Over a Barrel (BGM187)
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Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Fri Sep 13, 2019 11:50 am quote
Thanks for that; you can be sure I'll take care with it.

As numbers get closer to being fixed, I thought I'd have a check of compression ratio.
Doing calcs with recessed head and big PBT does get a bit fiddly, so to make it easier to picture (and reduce chances of me making a cock-up) I've taken deck reference point as being underside of squish band on head, and PBT (finished deck height) as squish (0.9mm). To check I was getting it right, I compared my results for 0.9mm Squish with BGM's; it's pretty close. I think my slight increase is either my method of measuring (I've done my best, but I haven't got lab kit; just basic stuff), the reduction in my head due to tidying up the detonation marks off the head squish band, or BGM's dome volume, which I just don't agree with. Anyway, the purpose of that first one was mainly to make sure I was using the right numbers, which I am pretty confident about.
Having established that, I did a new calc for the mods to raise the cylinder (and reduce head gasket) by 0.4mm, and cut the Exhaust port 1.6mm higher to get 125/181/28 (I note you say it may go higher; I'm just checking and keeping up to date with what we have now).

For 125/181/28 – 125/66, I'm getting CR=11.34:1 and CCR=7.03:1.

I'll just leave that there; the weekend forecast here is very good, and I have outdoor jobs to do on my scooter tomorrow, and hopefully time for a ride on Sunday, so, especially as I'm part-way through doing an engine build shopping list anyway, this job goes onto back-burner for a few days.

Here's images of method and working; should I clean the squish band more? I can take more out of the bowl to tweak the head volume if necessary:

Combustion Chamber Volume is 19.5cc.jpg
As accurate as I can; 19.5cc

CR 0.9mm - Check against BGM.jpg
Checking against BGM Data

CR 0.9mm - Check for 125-181-28 Including Exhaust mod.jpg
To latest tweaks for 125/181/28

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Sat Sep 14, 2019 11:17 pm quote
meniscus
Piston dome is a tricky one to calculate. Putting the piston in the cylinder and filling with oil to the top of crown will give the 'not dome' volume, which in terms of accuracy is second only to full assembly at TDC and filling through the plug hole (very messy).

Did you use a sheet of perspex with a hole to fill the head? If not the volume will be a little bit over with the surface tension adding to the volume.

0.9mm squish seems to work out well. The compression is right on where it should be for this kind of build. With another 0.4mm up on the exhaust things change slightly , so maybe 0.8mm squish would correct the deficit if going this way.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Sun Sep 15, 2019 1:07 am quote
I did it with and without perspex (for perspex, read clear CD cover with small hole drilled in it), the oil lifted perspex, so I lost some oil and there was still a small bubble under the perspex too, so I wasn't too happy with my method; (I got an imprecise 19cc that way). Had I been concerned about the result (CCC = 7:1), or had I known I wasn't going to clean the squish band more (should I?), I'd have done it again with the perspex weighted down (I'll do that in future). I'm aware of inaccuracy due to the surface tension meniscus; I still think my old method was more accurate – as I said, not a lab test; just a bloke checking some numbers. Had the numbers been close to limits I'd maybe have had another go, as it is I'm satisfied it's going to be pretty much 'right on'.

Yes, my measured volume is without dome, and my working in the spreadsheet calculates dome volume, and how much of that volume is within the combustion chamber volume due to squish. You'll maybe remember, from years ago now, I did it all long-hand with pen/paper/formulae/calculator the first time, then did the spreadsheet after I understood the maths, and made sure I was getting the same results with both methods.

When I said I don't agree with BGM, I was being polite; what I should have said is I think BGM is wrong; by my calculator, and two other online calculators (see image below) the volume for an r185mm*, h2.7**mm dome (partial sphere) is 4.2cc, but BGM states 1.9cc. Either they're accounting for squish and that's dome volume within combustion chamber, or its another typo, but I'm confident my number is correct – I was confident when I posted on Friday, and I've just checked it again this morning before posting. I think some difficulty arises from BGM half-calculating figures and giving data without being precise what it means, which is partly why I ignore them until I've done mine, then compare results afterwards.

*BGM state r185 in their data sheet
**2.7mm measured and cross-checked by drawing in ACAD; it's not wrong unless BGM's r185 is wrong (see image and calcs).

Little tweaks, like the exhaust final dimension, can be decided on and recalculated when I re-measure with 60 crank; what I'm doing now is checking over everything else (casings, gearbox etc.) to do a shopping list that includes as much stuff as I need in one order. ScooterCentre don't help because when something becomes unavailable, they just remove it from your shopping cart without warning, so I have to keep checking back! They've also been crap at simple technical queries. If they weren't cheapest, and free delivery over €199, I'd go back to Sip for the main order.

dome volume.jpg
Dome Volume = 4.2cc

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Sun Sep 15, 2019 7:50 pm quote
Not all domes are domes anymore. Many of the newer piston crowns are more like a pimple. These have the crown dome reduced in the squish band. This lowers the squish velocity. Doesn't make them quicker but does make them slightly torquier and way more reliable. If BGM are saying its 1.9 for the dome it just might be not exactly a dome at all. If it is this will drop the compression somewhat.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Sun Sep 15, 2019 10:06 pm quote
Maybe, but if that were the case it wouldn't be able to be defined as 'Piston Crown Radius 185', which BGM have clearly stated, also I measured to confirm the 2.7mm height.
If it isn't a regular dome, but some other irregular shape, then I can't calculate how much (volume) is in or out of the combustion chamber when doing fine tweaks.
I can fudge 1.9cc into my calcs and see the difference, but I think it seems unlikely to be less than half of the regular dome volume (4.2cc); I'm more inclined to think it's a BGM typo or dome in combustion chamber (after dome in squish removed) - I know it wouldn't be a constant 1.9cc, but it's a feasible explanation of what they may have done there, and maybe explains why it's less than half the actual dome volume.
Let's also not forget that I've been rubbing out the detonation marks, so if ever it had some other shape, it might be in my vacuum cleaner now (it still looks like a dome to me).

Anyway, an interesting point, but no point getting bogged down on it if it is unknown; I've recorded the discrepancy and will keep aware of it in future calcs.

I've inserted a photo of my dome profile into the dimensioned ACAD drawing I posted yesterday; I think it confirms it's a dome (or at least that it isn't less than half the volume of that dome):

Piston Crown in ACAD.jpg

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 7101
Location: Victoria, Australia
Mon Sep 16, 2019 12:14 am quote
sime66 wrote:
If it isn't a regular dome, but some other irregular shape, then I can't calculate how much (volume) is in or out of the combustion chamber when doing fine tweaks.
I have used a method to calculate volume using Play-Doh - not sure if that's a thing where you live but it's a bit like plasticene or modelling clay, but softer if memory serves. You can put it into the greased bore in a ball with the piston above the exhaust port, then rotate the crank like you'd measure squish. You should have enough in there so that some will ooze out of the spark plug hole. If you've greased it up it should come out easily enough... guess you would have to make an allowance for the plug.
Then you drop it into a container of water that has an accurate measure on he side and calculate volume from that.
I couldn't find the right stuff for my test and made some from a recipe I found, but it ebnded up way too sticky and inconclusive, and pushed my persistence level to slightly beyond what I thought was reasonable!

If you can't be arsed doing that then you could just push the piston into a lump of Play-Doh and measure using oil like you are doing with the head already.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Mon Sep 16, 2019 12:33 am quote
I think my photo/drawing above shows it is a dome, and you're right I could prove it by making an impression and measuring it, but all evidence tells me my 4.2cc is correct, and the more I investigate it the more 'not-a-dome' theory isn't as convincing as 'BGM-typo' theory.
To try to prove it I calculated the dome volume (in chamber) for 1mm squish (BGM's rec.) to check; this gives a dome height of 1.7mm and a volume of 1.67cc - this is what I think BGM are trying to give, but as I said above, that volume depends on squish, so the 1.9cc is best just ignored.
Or, looking at it another way, from the image and dimensions above, what's the working to achieve 1.9cc?
Your first method is fine, except we'd probably spend another week arguing about the volume of a spark plug!
Time to move on, I think.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Mon Sep 16, 2019 8:15 pm quote
Looks like a standard dome to me too. So, BGM info is wrong. Measuring it won't be any different to the calculation. Decide the final squish on the dry fit.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Wed Sep 18, 2019 11:57 am quote
Moving on....
I've been giving the casings a bit of TLC – I wanted to give them a thorough check before doing my big order, which was dispatched today. I've cleaned-up all my stud threads, decided what needs replacing, ground out the flange that obstructs the Cosa clutch (and on the clutch cover too), and am going to hoik the silent blocks out next job before having another good scrub, ready for the Dremel; it's not an imminent job, just something to think about whilst my stuff is on its way from Germany.
So, my mind wandered to the Transfers in the casings, and as a starting point I dug out the base gasket template for the casings for my DR engine.
On the images below, I started by using that template to mark those transfers in green on the casings and the barrel; They seemed big at the time, but it looks like I can do a fair bit more with BGM177.
On the barrel, in red, I've marked where the mating surface restricts the transfers already cast, and can be removed (where corresponding cutting of casings is possible to match). Then on the casings I've superimposed (just by eye for now; I'll make a template after I've done the barrel and seen how far I go) those extra cut-outs on the casings.
They will need filling behind with JB Weld first, particularly on the main casing; I did this before on the DR engine, and although I didn't break-through anywhere, the JB Weld has held well.
So to recap; the green is to match the DR casings (taken from the base gasket template), and the red is from looking at what more can be gained by using all of the cast-in Transfers by removing metal from the mating surface. I'll need some guidance about how much skirt to remove, especially as it's a Nikasil barrel: leave where it is, take flush with mating surface, take below mating surface into barrel? – see DR image at bottom for example of that, which is what I did before -. swa45, I saw that you left the skirt alone; probably wise, and I've seen your finished casings (17 Jul), which is about how I expect to finish up; pretty-much my red dotted line.

BGM 177 install (Page 3)

Will I go BIG to the red and rely on the JB Weld? Or will I tone it down a bit, especially as my Inlet is, though still adequate, not as big as the DR casings Inlet due to the timing on the l/s crank restricting the Ic cutting? I suppose as this is 187cc, I'll be going big.
Some images below, with asterisks marking areas that look like they won't allow full opening to transfers in barrel without relying on JB Weld.

To pre-empt other queries potentially arising from photos:
The white marking inside the barrel is grease not wear in the Nikasil; don't worry.
I haven't done the cylinder studs; I have new Piaggio ones, which I'll Loctite in, but that's much later on.
Yes they're a matching pair – 209.

Transfers in Casings.jpg
Asterisks where it looks like JB Weld might be needed

Transfers in Barrel.jpg
Green is little DR, Red is BIG BGM!

DR Barrel Skirt.jpg
Skirt detail for DR - what to do with BGM skirt though

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Thu Sep 19, 2019 12:57 am quote
BGM base transfers are a bit small. I think we'll have bigger ones.

Green line should be enough. Not worth going through the aluminum, just leave the JB weld as support. As big as possible without going through.

Skirt can be same as the DR. Right in. Plenty of Dremelling practice before doing the exhaust port.

transfers_in_barrel_13742.jpg
Cut these bits out of the skirt. Keep the same round edge

Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Thu Sep 19, 2019 12:50 pm quote
Thanks Jack; nice and clear, no questions arising from that. I'd also thought it might be a good place to practice the Nikasil before the crucial cut.
Silent blocks are out; they tried to resist, but it's a job that gets easier the more times you tackle it.
The exhaust port in the barrel is pretty coked, so I'm going to clean that whilst waiting for the parcel. I also noticed that the exhaust stub is slightly deformed, over-tightened I imagine; I've shown it in case it's a concern, and I don't intend to weaken it more by reshaping, but it's here for comment if necessary. My exhaust is on springs, so I hope it won't be an issue, or maybe some sealant in the gap if it is.

Barrel Exhaust Inspection.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Fri Sep 20, 2019 12:03 am quote
That exhaust port carbon is probably costing a few BHP. The jetting before must have been quite a mess. Rich at the top and lean at the bottom is most likely.
By the time you have re-worked all the base transfers, you'll be so happy with cutting Nicasil you'll be working out how to drop the transfers at BDC.
Exhaust stub annoyingly normal. Usually is ok at the exhaust ring is in the middle and the deformation is less up there. Might be a JB weld option if you have time.
https://www.amazon.co.uk/JB-Weld-8297-DEU-Heat-Resistant-Temperature/dp/B010LMLS3E
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Fri Sep 20, 2019 12:46 am quote
Plenty of time!
(But Rugby World Cup starts today, so ask me again in a few weeks....)

I saw that High temp JB weld last night, so will get some; keep the aluminum stub deformed and reshape the outer?

£8.49 on Ebay (JB Weld 8297):
https://www.ebay.co.uk/itm/J-B-WELD-STEEL-STIK-WATER-WELD-HIGH-HEAT-WORLDs-STRONGEST-BOND-EPOXY-PUTTY/173425914080?epid=2187392870&hash=item2860fd70e0:m:mFj0WD7I9T4wxVjUWTRwyKA

Had first bash at cleaning up the exhaust for half hour earlier this morning after soaking it overnight; looking much better already – going near the Nikasil lip is a bit scary, so I knocked it on the head when my hand got tired and started to miss.

Next job; unpacking SC parcel, which is due today.

(Found a few horses already! - I noted, with a smile, the comment about Transfers at BDC; dry build with l/s will shed more light on that no doubt....)

cleaning exhaust.jpg
looking better already

Member
Motovespa P200e
Joined: 23 Aug 2018
Posts: 8
Location: Muffspeed, Derry, Ireland
Fri Sep 20, 2019 2:10 am quote
Nice thread folks, following intently. Have a couple of BGM177 engines to build for club mates over the winter so this will be of great help
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Fri Sep 20, 2019 12:04 pm quote
Hello, Boomshakalak; Derry looks a nice spot for a buzz round on a Vespa; I see Muff on the map, is that your home, just into Ireland? I expect you'll have your engines done before me; I like to go slow and steady with all this stuff 'cos I'm not really all that sure what I'm doing.

Back to the plot; for this evening's little task I've checked the timing on the l/s Mazz crank, which arrived earlier today; it's not exactly as I expected, but still OK.
From measurements of my rubbing, Io = 7° Ic = 137°, giving actual opening of 130° (I'd reckoned on 132° from published data); anyway 137/7 is close enough.
But both cuts on the crank are angled, so there's a bit more; the start of the Io is earlier (by 3mm), and end of the Ic is later (by 5mm); adding that difference into my measurements this corresponds to 9° more inlet duration, finally closing at 142.5°, not 137°; so now actually Io = 3.5°, Ic = 142.5°, total opening in crank is 139°; 142.5/3.5 - that's first opening to last closing – or should I use when it starts to close?

Looks like my previous Inlet timing 125/66 will end up more like 125/71, but I guess that's OK. It'll all get checked many times more before any cutting, and I'll confirm with degree wheel too.

Next job is another dry build with l/s for PBT, squish etc. and pin timings and gaskets down.

Quick image of crank, with a few dims and angles, for the record.

My Mazz Longstroke Marked with angles - 142-3 - ACAD.jpg

Member
Motovespa P200e
Joined: 23 Aug 2018
Posts: 8
Location: Muffspeed, Derry, Ireland
Sun Sep 22, 2019 11:55 pm quote
Sime it`s a lovely spot, 5mins from the border and Donegal which is spectacular for a day out on the scoots. Used to live in Muff running a small resto shop hence the Muffspeed name.

I`ve been catching up on all the old threads on here and can safely say you know fine well what you`re at now from all the coaching from Jack.

Any way I`ll be following this as i do most of the engine build threads and will join the party and start a thread when I get a start on my Polossi 210 build
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Mon Sep 23, 2019 1:52 am quote
I think 125/71 would be a very good place to end up. Any Dremel work over the weekend?
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Tue Sep 24, 2019 4:01 am quote
OK, who broke the forum last night?
It's true, Jack has been a great tutor, so it's about time I got the hang of it, but I do still like to have someone making sure I don't do anything stooopid.

Here below is an update of all current facts and figures, together in one post, after checking dry-build with l/s crank. These will be the figures I'm working to now. I've triple-checked PBT (feelers, vernier, depth gauge) and I'm happier with my accuracy now, though it didn't change the result. At the bottom, I'll put some images, which aren't critical to following the plot; just an update of current numbers, which it helps me to refer back to when I'm checking myself. There's also a photo showing Base Transfer skirt mod potential, which shows BGM already allowed for it in the piston cut-outs, bless 'em.

Measured PBT: 3.1mm (no gaskets).
Finished PBT: 3.9mm.
Finished Squish: 0.85mm (Note 1)

Finished Timings: 125/181/28 & 125/71.


Exhaust raised 1.6mm to achieve 181° (Note 3)
Bottom of Transfers may drop about 0.59mm to be flush at PBT (Note 2)
Base transfers widened to suit casings/barrel mods, and dropped about 8mm to top of splitter in Transfer channel.
I've done a sketch of piston/barrel alignment at TDC and BDC, which might highlight any other mods to barrel/piston; I'll tweak it as I go – I need to check the boost Transfers, missed a measurement.

Base Gasket: 0.8mm (0.6mm Al + 0.2mm Cu for tweaks)
Head Gasket: 0.8mm (0.5mmCu + 0.3mm Cu for tweaks)

C.R. = 11.43:1, C.C.R. = 7.08:1.

Notes:
1) I need to make a base gaskets before I can confirm Squish; 0.85mm is a compromise towards 0.8mm and makes the base gaskets work well.
2) Again, I need base gasket to confirm this, and maybe it's too small (within the existing chamfer) to bother with and risk the Nikasil in such a confined space with difficult access for Dremel, when the Transfer bottoms are all straight, neat and chamfered as they are – is there a real benefit from it?
3) Will shape of top of Exhaust be the same, or bulgier with a flat middle section?

Rough order of next jobs:
Make base and head gaskets to check squish and BDC level before removing old cylinder studs – base gaskets roughly as DR template, but will get modified more as I do transfers in barrel and casings.
Remove old studs and check/clean threads.
J.B.Weld casings.
Use base gasket as template to open transfers in barrel and casings, transposing any tweaks from one to the other as I go, so all three are the same when done.
Finish base transfers in skirt to suit base gasket width and down to top of divider in barrel transfers.
Cut exhaust port top in barrel (having practiced on skirt).
Decide about bottom of transfers at BDC. - What about exhaust BDC?
Fix exhaust stub with J.B. Weld High Temp; I've bought this and made a ring to use as a mould.

Then on Wednesday..........(Seriously, that list will take as long as it takes – this is a winter project, now I have all the parts and the design I can go at my own pace).

After the list I'll go on to the Inlet; getting it smooth through carb, carb box, casings, and opening casings (and cutting crank) to achieve 125/71. The gearbox should be fairly straight forward; I've inspected it all and checked driveshaft shims/end play. I will need to re-do cush-drive with both sets of springs, but fitting full EFL into P150X isn't going to be a problem with the stepped primary shaft.

Here's some images, drawings, calcs and photos - mainly for me to refer to later:

1 Port timing for TD125 AND Bd 28.jpg

2 Barrel Dimensions and Compression Calcs.jpg

3 Barrel Cuts.jpg

4 Crank Timing calculator for 125-71 with ls Crank.jpg

5 Barrel Base Transfers mod.jpg

6 Cutting Gaskets BGM187 125-181-28.jpg

Inlet timing Crank and Pad mods.jpg
(not changed, just checked and added to post)



Last edited by sime66 on Thu Sep 26, 2019 1:16 am; edited 2 times in total
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Tue Sep 24, 2019 7:37 pm quote
This is coming along quite nicely. I would doubt the DR engine will be your favorite once this BGM is alive.

Exhaust port at BDC should be flush across the centre. This improves torque, power and temperature, so it matters.

Transfer ports at BDC are a subject of much controversy. If they are flush great. If they are not who cares. I make all the ones I do flush (or nearly, depending on packer of the day). I think for yours the risk benefit doesn't stack up.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Sat Sep 28, 2019 12:00 pm quote
Jack221 wrote:
I would doubt the DR engine will be your favorite once this BGM is alive.
The problem with that thought is that the DR is going so well at the moment I'm not going to want to go through the hassle of swapping over until something goes wrong; it's taken quite a lot of work to get it right. I'm not going to worry about that yet, I just want to enjoy having the build to fiddle with over winter.

Very quick update; all going to plan.
Gaskets all made.
Squish closer to 0.9mm, but main base gasket is also a little thick, so when that's finished and cleaned-up, and PBT exact at 3.9mm, the squish will be spot on – easy enough.
Old studs came out clean and free of any bits of casings thread. Threads in casings are all good, and I was able to screw in M7 bolts, which I'll use to hold gasket as I match it to casings. I didn't need to run a tap down them, but I'll do a thorough clean before fitting the new ones; I'm leaving them alone as much as possible 'til then.
I've JB Welded casings; I'll tidy them up when it's properly dry; it was still too tacky to sand this morning before I photographed.
I've repaired the exhaust stub; that High-Heat JB weld seems very good – if it stays in place while I'm Dremelling the barrel it'll be a good job.
Next job is to do the casings to 90%, and then match the barrel and tweak that to any obvious extra cuts I can do without going through the casings. Then finish the transfers in the casings, cut barrel skirt, cut top (timing) and bottom (flush BDC) of exhaust, and crank case inlet pad and crank work (I added a drawing of that in previous post above with other sketches and calcs).

This morning, though, I had a few jobs on the scooter outside; my new rear hub was getting quite hot – I had a good dual carriageway run last Sunday – cruising 7000rpm 4th and 162°C, which is nice for me, the detune has taken about 10 kph off top speed but I'm happier at 105 rather than 115kph anyway especially as CHT is under control now, but I noticed the hot hub after. I made sure it was still torqued, then took it off, see if there was any odd rubbing, made sure it was still tight and both splines are still OK, and torqued it more than before with a long bar and an interested dog-walker (I get a lot of passers-by stopping to talk to me now I'm working in a car park), who I volunteered to help by sitting on the scooter with the brake on so I could really lean on it – I was pulling it across the car park last time, trying to do it on my own. Of course I used a new split pin and the hub spins freely when jacked up, so it isn't rubbing anywhere – should be sorted; might get to test it tomorrow.

That's about it, other than a few photos – no proper cutting this time, but next post should be more 'swarfy'.......

1 Base Gaskets.jpg
Base Gaskets

2 Head Gaskets.jpg
Head Gaskets

3 All Together.jpg
All Together to Check Squish

4 Studs Out.jpg
Old Studs

5 JB Weld Jobs.jpg
J.B. Weld Where Needed

6 First Cuts.jpg
Time to Make Some Swarf!

Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Mon Sep 30, 2019 1:36 pm quote
A little progress; I'll transfer this much over to the barrel, open it a bit more if I can, then tidy it all up before going onto the crucial bits – skirt first to get the feel for Nikasil.
I also updated the barrel cutting drawing to remove BDC Transfers, and include BDC Exhaust.

2 Transfers 90 percent.jpg

Barrel Cuts.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Mon Sep 30, 2019 11:59 pm quote
Looking much bigger already. Think that will be plenty. Once the barrel is on its all going to look way bigger than the original BGM. Doesn't look like you went through to the JB weld either. Sure its close but not through.
Inlet next or cylinder?
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Tue Oct 01, 2019 7:40 am quote
I'm going to finish the mating surface and base gasket next; it's a bit of a mess top and bottom of these ports where previous chap has had a half-hearted bash with a little flat needle file. This will make the base Transfers a little wider than I currently have in the casings, and will need to be matched in the skirt too. I'll probably have to finish the skirt while I sort it, but not the exhaust port yet because I'm not sure if I have the shape of it correct. The Inlet pad and crank don't really worry me much; most of the pad opening is with files, it's time consuming, but not much chance of messing up.
These are the areas I'm trying to tidy next; I've just bolted it together and am having a bit of a think about it for now, with cast iron I'd just plough the opening in the skirt straight down through the lot, but with Nikasil I just want to go at it a bit more carefully; probably get rid of as much meat inside the port as possible, without touching the Nikasil, then work straight, down the skirt when it's thinner and I can concentrate on not messing up the edge........

Base Transfers in Barrel.jpg
Messy corners to tidy

Base Transfers in Barrel Top View.jpg
Perhaps not as wide as I'd initially thought

Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Tue Oct 01, 2019 7:47 am quote
Swa45 and Hibbert, I've seen you discussing Nikasil cutting, and not sure which thread to post this on, so hope you see it here; there's a chap on Youtube who suggests a diamond burr or sanding stone to take the Nikasil off the edge before using the carbide burrs, and elsewhere I read a blunted carbide burr is less likely to grab and chip; this seems like a good plan to me. So, on mine, where I need to take about 1 - 1.6mm off, I'm going to start by removing the Nikasil from the edge with those cheap diamond cutters or a stone – whichever works best, and then remove the meat with a carbide burr as usual. It'll still take a bit of practice to get tools and method right, and I have the skirt to practice on, but this seems sensible and achievable with care:

.
For those using Chrome: "https://www.youtube.com/watch?v=8zIUhIrNk14"

http://www.macdizzy.com/update102.html

Cutting Tools.jpg
I have a plan.....

Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1216
Location: UK (South East)
Tue Oct 01, 2019 8:02 am quote
I hate those bloody corners on the BGM base transfers!

Thanks sime for taking the lead on this. Although I may not open up my MHR exhaust port just yet, I am still going to get some practice with the [almost] scrap cylinder that I have (Pinasco Magny Cours).

Back story: I was trying to keep elestart with the Pinasco, so shaved the side transfer to accommodate the flywheel gear. Must have shaved a little too much, took it for a thrash and blew a big hole in the transfer. I got an 'expert' alloy wheel specialist to repair it with weld, but he managed to warp the gasket face
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Tue Oct 01, 2019 10:52 am quote
Ouch; that sounds like an expensive lesson.
I'll stick to chopping up old stuff and watching the rich kids play with the big-bucks parts; the most expensive part of my build is the crank, which cost the same as the kit and casings combined – I'm strictly low-stakes, and I'm still a bit sore that I didn't manage to use my old 57mm crank to make it even cheaper!
I won't have corners when I'm done; it'll be a 'T'/'L' shape there as the skirt carries on down past the mating surface – I can picture the end result, it's just figuring how best to tackle it, and a bit of hands-off cogitating for a while helps me not make a (cheap) doorstop.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Fri Oct 04, 2019 6:04 am quote
Work in progress:
This is 1st pass with a Dremel 952 Stone (aluminum Oxide - pink), for 45 minutes this morning (top photo), which is about the limit before my hand is too shaky to trust not to slip. It's a slow job. Even being really careful, I've had two roughly 0.5x2.5mm flakes, but had enough room left to cut to put them right; it ain't a job I fancy much when I've only got the narrow cut on the exhaust, and no room to clean up flakes; I'll see how the diamond cutters work when I get to cleaning up, and maybe use those on the exhaust. Still plenty of time left doing these to practice and get better at it, but I reckon only about 50/50 chance of completing the barrel without a nice doorstop. I wouldn't choose to do this on an expensive barrel myself.
I've also got into the corners of the mating surface with a narrow carbide bit; it still looks untidy for now, but I think this side of the job will end up OK. Very slow and steady with the Nikasil though.

...Had 2nd pass with Dremel; another 45 minutes this afternoon (bottom photo). No more flakes, so maybe my method is improving (doing the Nikasil surface first about 1mm, then the 'rough side', then flatten and repeat), but also, as I go below mating surface, it's getting trickier to get an angle with Dremel and stone that doesn't threaten something else – very tricky. There might be a point to accept going further might not be worth the risk, but for now I'm going to get the other side to this point – a couple of hours. I'll see if there's any feedback before going further with this side; it'll all get a final tidy and straighten up of sides and corners when overall size is final; want to try to get the skirt window past the mating surface to get the corners really tidy. Optimism for exhaust port improving....

Base Transfers in Barrel 1st Pass Cutting Skirt.jpg

Base Transfers in Barrel 2nd Pass Cutting Skirt.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Fri Oct 04, 2019 7:29 pm quote
All going well by the looks of it. Those windows can go down to the divider, so still a few 45 minutes sessions to go. If you frequently oil up the carbide burrs they don't clog up so much and cut faster. Wouldn't be over concerned about the Nicasil until a few mm from the end but good for practice. I like the cheap diamond burrs for the fine work. The cheap ones are better for finishing as they hardly cut.

This is going to turn out way quicker than the DR. You're not going to be able to not run it.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Fri Oct 04, 2019 11:01 pm quote
Cheers Jack; wet and windy weather forecast is perfect – for aluminum mining...
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Sat Oct 05, 2019 6:55 am quote
It's not often I'm upbeat about these things, but I'm actually pretty happy with this now, so I'm going to get the other one to this point, then we can decide whether its enough or not; gone 6mm lower today, so 9mm in total to 39 chord x 37mm now. I think the other side will be quicker now I have a feel for it, not that time is an issue, but every session is a potential cock-up. If that goes OK, I think I'll do the exhaust before the Pad Inlet; might as well while I've got my eye in. Still a long way off yet anyway.
These photos are not the best, so I did a quick film to give a bit of a 3D feel:

.
For Chrome users: “https://youtu.be/eSunDHvHzZ8”

Base Transfers in Barrel Millionth Pass Cutting Skirt 1.jpg

Base Transfers in Barrel Millionth Pass Cutting Skirt 2.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Sat Oct 05, 2019 8:56 pm quote
I would go a little bit lower yet but looking good. Nice and smooth ready for shining up. The bore wall on this cylinder is way too thick. It doesn't need to be like that with higher transfers. If you get a long carbide burr down each of the 4 transfers a few mm could be taken out of that thickness between the transfer and the bore.

Yep. Go straight into the exhaust once the base is done. If you do the exhaust BDC first for a last practice, then into the 'all or nothing' stage.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Sun Oct 06, 2019 11:32 am quote
Another 5mm; flush with the lowest part of the divider, which now forms a wonky 'T'-piece with the bottom of the window. Opened inside both channels, mainly by removing from cylinder wall, which was thick, and was causing the difficulty going lower as you spotted. I can tidy the inside of the walls up to get even thinner and a more constant thickness (I see more bits needing a little tickle when I check photos), they'll get a tidy as I match both sides of the barrel anyway, but that's as far as it's going for today; other side during the week....

Any change needed from original shape of exhaust port, or just same but higher and lower?

.
Chrome users: “https://youtu.be/UQgQPfytJd8”

P1100308.jpg

P1100324.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Sun Oct 06, 2019 11:50 pm quote
Don't they look big now? That side is plenty large enough. Was really getting in the way. You just swapped some bottom end torque for mid range power. Will go way better on the road.

Exhaust shape is already quite sporty on this. You should just work on the centre 3/4 and leave the edges to reduce the risk of chipping. The overall shape will look slightly rounder but thats the kind of performance I think you're after.
Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Mon Oct 07, 2019 11:17 pm quote
Thanks for that, Jack; fairly confident about the exhaust now, and below is a view through the opened casings to show just how BIG it is now; it was mainly to check where else needs a tweak, and I see a few little areas. Unable to post yesterday – the forum was down again, so my mind went back to a note I'd seen in the Mazz crank instructions.....

Main reason for this post then, and I'm bracing myself for more expense, is the subject of flywheel weight. I'm aware of pros and cons, and have read all I can find to refresh my memory of the subject.
On my DR engine, which has an old Piaggio flywheel with the starter ring taken off, I have none of the downsides of either too light or too heavy; it seems perfect to me as simply not being an issue.

The instructions with that bleedin' Mazz 60mm crank, that I didn't even want to buy, says that a 1600g flywheel is max:

'to avoid great vibrations and the inevitable breaking of flywheel shaft'!
(they make something knowing the shaft breaking is inevitable!? - made me think of your's again).

Anyway 1600g seems very light, but the flywheel I wanted to use, with the ring off, is 2100g.
I looked last night at options, excluding Pinasco plastic, HP4 and anything with reduced fins, ranging from 1600g to 1900g (Sip Touren 1600-1900g/PKXL 1750g-small fins though?). So question(s):

1) What would be my perfect flywheel weight?
2) What would be my max weight (surely not Mazz's 1600g)?
3) Is my 2100g flywheel definitely too heavy?
4) If I thought about removing some mass from this flywheel, if I need to, how much would be ideal? - Seems it's this, or a Sip option, or back to drawing board with 57 crank.

I'm not interested in the performance upsides of being light, and am aware of the downsides of it. I like the pros of the ~2kg flywheel I'm using now, and this build is not intended to be much different, but I can't use something I know is too heavy for the stress it's going to put on the weak crank.

If the cost of the decision to go 60mm has just doubled because I need a flywheel to go with the weak crank, then I'm going to look again at sticking with 57 crank; I don't want to buy loads of shoddy new stuff, and still be left with a load of good unused stuff, when the aim of the build was to use it.

Of course, this won't matter unless I do the exhaust without messing it up, but that'll be last chance to re-think crank.

Opened Transfers in Opened Casings.jpg

Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Tue Oct 08, 2019 5:52 am quote
I've had a read back through the previous incarnation of this engine design, and I was told that flywheel was too heavy before, so have to wind-back previous comment there; I should have remembered.
However question remains whether I need to go as light as Mazz's 1600g. Below is a list of options in weight order, all options that I can find involve smaller fins, which after the battle I had getting DR cool without too much loss of performance, seems like a bad idea. It would seem that getting mine lightened would enable me to keep the full fins (subject to deciding on an ideal weight, and there being enough meat to remove without chopping the front face), and would let me use this flywheel, which would make me happier, not for the sake of £130, but because using the old stuff makes me happy. Having to farm out a job doesn't make me happy, but I seem to have to have something lighter than 2100g, so it's that or new.
Also, if 1600g really is the ideal weight not to shear my chocolate crank, then what's going to break instead (clutch/primary springs), and will it be so bad to ride like 1100g HP4? I particularly do not want to build something that is worse at climbing; I'm a big chap and I live in a hilly part of the country, I have a 16% hill just 2 minutes up the lane from me, and I climb it easily in 2nd at 6500-6750rpm – throttling back to keep revs low because it just can't quite get on top of 3rd – that's my benchmark.

Here's my list, at present I favour lightening my Piaggio 2100g flywheel, but if so, by how much?

Flywheel Options.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1557
Location: London UK
Tue Oct 08, 2019 6:56 am quote
Base transfers looking good. Back to the casings to line it up better and round off the sharp endges.

Flywheel. 1600g is about the minimum you want. 1900g about ideal. Wouldn't worry about what Mazz says. Safis turns down his own maybe he'll take 200g out of yours for some euro beer tokens?
Molto Verboso
1979 P150X, 1983 P200E, 1987 T5, 1996 PX200E, 2011 Yamaha Fazer 600 S2
Joined: 02 Aug 2015
Posts: 1619
Location: Veria, Greece
Tue Oct 08, 2019 8:11 am quote
My second one (Red) came to 1830g. Took a bit between the fins to clear the missing pieces after someone had used a flat-head screwdriver to take out the flywheel. Started from the surface the starter ring sits on and moved inwards. Stopped at the green arrow on the second photo (there's a metal core that also holds the magnets that starts from there). This way you don't mess with its' balancing since you're taking out solid aluminum (I had mine checked before and after machining and they balanced the same). If you want to keep the dust seal you can start after the outer lip (red arrow). To mount the flywheel onto the lathe we first skimmed a "hair" of the rivets from the outside so to bring the flywheel "parallel" to the lathe. Then we mounted the flywheel puller and used it to "catch" the flywheel to the lathe...

IMG_1314.JPG

IMG_0532.JPG

Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Tue Oct 08, 2019 10:09 am quote
Thanks Jack for the magic number; makes it all seem far simpler, and more sensible than 1600g.
So cutting this one it is; happy with that, and my first thought was where to start and finish, and how to make sure it's balanced, and your post, SaFiS is so helpful there; thank you very much indeed for doing that – it's like you read my mind with my next thoughts before I'd even managed to even get them organised in my head. Then using the puller to mount it on the lathe – the solution to something before I've even thought of the problem.
I'm looking at the same item, can clearly see the indent where the magnet-holding core starts, and that the balancing is inside that. My fins, and the webs in between are intact, so cutting there is optional, and dust isn't an issue, so again it's whether or not I need to lose the weight there – mud and cow shit is more of a problem here than dust.

It is 2120g now, so allowing some tolerance whilst cutting and weighing, if I said:
Not less than 220g to remove to give 1900g target.
Not more than 270g to remove to give 1850g.
Start at whichever red arrow achieves this, but don't touch the fins.
Don't go inside Green arrow.
It'd be pretty hard to get wrong.

Thanks very much chaps, I'm glad I asked; it's been nagging at me since I saw that Mazz sheet a couple of weeks ago.

Back down the aluminum mines for me tomorrow afternoon, make some progress with the barrel.....

My Flywheel Marked up.jpg

Hooked
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 201
Location: Cornwall UK
Fri Oct 11, 2019 8:31 am quote
I've found a friendly chap to do my flywheel; a modest little machine shop a 15 minute walk from me:

https://www.jamespinderengineering.co.uk/

He listened to the cunning plan, asked a few questions, and showed me round his workshop and what he's working on, and we're going to cut the flywheel together on Monday morning. He's got lots of nice toys, so should be a good contact for any future jobs too, if all goes well I might get him to media blast it to make it shiny.

I also finished the second of the base and the boost transfers yesterday afternoon, subject as always to a final clean-up when I've checked my photos, I've matched and finished the base gaskets, cleaned them up, and transferred the final tweaks to the casings, done dry half-case builds to check and tweak, so that job is done (some photos at the bottom, which it will inevitably lead to more work when bits I've missed are pointed out to me, and which have been updated a little since I took these anyway, and not too important now, especially as I've worked myself up to tackle the exhaust now).

After a good de-swarfing of everything so I didn't scratch the barrel, I put crank and piston back in, re-checked PBT and squish, and then marked how much needed to come off the exhaust port at BDC (drawing/calcs says 1.55mm).

PBT is perfect now, squish still a little over, so that's just a small tweak of head gaskets needed; I'll do that when the cylinder studs are Locited in and I've done full-torque. I can swap the 0.3mm for a 0.2mm if it proves necessary; no worries, I've just made a note to check when the time is right; it will be spot on when I'm done. My studs are fairly loose, which isn't a big problem, but I want to install and remove them as few times as possible until it's time to Loctite them in; after this measure and tweak, and after the exhaust port is finished, I think they can come out for good until final build.

I marked Exhaust bottom at BDC, then cut very gently until my hand was too tired to continue without risking a slip. By eye it was almost there, and by measurement bottom to Deck = 63.4mm, when it should be 63.85mm, so just a tiny bit lower to go sometime over the weekend and that job will be done.

So, there's no getting away from it, the time has come to do the crucial cut. To follow next then, all being well: completed exhaust (top and bottom), and lightened flywheel.......

1 base transfers.jpg

2 matched to barrel.jpg

3 matched to casings.jpg

4 exhaust at BDC marked up.jpg

5 exhaust at BDC first cut.jpg

Addicted
Honda elite
Joined: 19 Jun 2007
Posts: 631
Location: California
Fri Oct 11, 2019 9:27 am quote
it looks spectacular sime66
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