Cylinder vs crankcase (reed) induction
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Molto Verboso
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Fri Mar 29, 2019 2:43 am quote
I have decided on a PX125 gearbox with 21/68 primaries and a 130/70-11 rear tyre. I'm using a 57T 1st from a P2 (PX125 is 58T) to make 1st gear a bit longer and I am considering a 40T 2nd to extend 2nd and bring it closer to 3rd. However, the 40T Crimaz or DRT cogs are quite costly. Would this be a good move and would the difference be enough to justify 100 on a gear cog?
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Fri Mar 29, 2019 5:02 am quote
The gearing will be a pain but as yours will be fully opened out reed valve and a 39mm carb, it should less of an issue. 21/68 with the big wheel is a good place to start. Ride it before you waste any money. Mine is in 2nd gear for about 2 seconds when accelerating away.

I have a feeling the 1mm packer is too much. It would be for mine but with your lower crankcase pressure it could just about be ok.
Expect high power and lots of rpm. When I tried mine with the higher duration's it was going way over 9000 rpm. GPS 70mph in 3rd gear
Molto Verboso
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Fri Mar 29, 2019 6:55 am quote
Cheers Jack. I have the option of a 20T clutch if needs be. Any other changes would require the cases to be split, so I'd like to get the core gearbox right first time.

As it stands, I have the 1.0mm packer under the cylinder, without the thin gasket which came with the kit, so the cylinder is only raised 0.8mm higher in real terms. This puts the piston 0.9mm out of the bore at TDC. With the 1.0mm head packer, I think I'll have exactly 1.0mm squish with the stock Malossi head. Final measurements with this setup give me:

Distance from top of bore to transfers: 45.5/45.3/45.5 = 45.4mm average
Distance from top of bore to exhaust: 31.8mm
Deck height to top of piston: -0.9mm
ED = 185.58
TD = 129
BD = 28.29

With this in mind and the planned gearing, would you advise a full-on expansion or do you think that a box like BGM BB Sport would still be a possibility?

On the subject of the base gasket, Malossi had included the one for what looks like the old 210 kit or maybe the Sport. The cutouts don't match the cylinder, as the side ports are quite a bit bigger on the MHR. The 1.0mm BGM packer cutouts are a perfect match.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Fri Mar 29, 2019 7:54 pm quote
A stock 200 ratio box with a 36 4th is everyone's favorite. I have 200 box and a 35 tooth 4th in mine as I am often on the motorway. If you put the 36 tooth in with your 68 primary, I doubt you will need to change it.

Be sure to measure your squish clearance. From those numbers I would guess 1.5mm!
0.8mm base better but still maybe too much. The more rpm the higher the powerband starts. Means thrashing it everywhere and this gets tedious. That said, I do think the MHR is not as high rpm orientated as they would make us believe. It's still pretty much ported like a motorcross bike to keep broad power because of the 4 gears. The issue for sure with the MHR is the secondary transfers, the higher these get the more gearbox issues there will be.
I have changed my packers 5 times already (mostly for the science). I have possibly the last planned for when I get home
Molto Verboso
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Posts: 1571

Fri Mar 29, 2019 9:32 pm quote
Re: Gearing dilemma
swa45 wrote:
I have decided on a PX125 gearbox with 21/68 primaries and a 130/70-11 rear tyre. I'm using a 57T 1st from a P2 (PX125 is 58T) to make 1st gear a bit longer and I am considering a 40T 2nd to extend 2nd and bring it closer to 3rd. However, the 40T Crimaz or DRT cogs are quite costly. Would this be a good move and would the difference be enough to justify 100 on a gear cog?
I'm not sure, but with a 130/70-11 tire, you might have to grind down the webbings on the swingarm so that the tire doesn't rub against it. Also with that huge 130, it's going to sap power quite a bit just because of the shear size and weight. Yes you can change to a more optimal gearing, but the rolling resistance and weight of a tire that size will definitely require a lot of torque.

You probably wouldn't need to change tooth count the 1st through 3rd gears. Most engines (even a stock 200) will pull fine through 3rd gear with an oversized tire...it's just 4th gear which saps all the power. I think DRT still makes a 37 tooth super short 4th? You might look at using a 120/70-11 instead? It will look awesome tucked under there as well, but your engine will be able to pull better with that smaller diameter tire. I've had a oversized tires on 3 different motors, and I've always been fairly disappointed with the performance. I finally went to a super wide tire (110/70-11) whose diameter was close to a 3.5x10. Anyhow, just something to think about.
Molto Verboso
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Sat Mar 30, 2019 12:16 am quote
No matter how many times I measure it, I'm only seeing 0.8mm (maybe 0.9mm) squish in the stock MHR head. Therefore, to get squish to the recommended 1.2mm, I'm going to need the piston to stop at least 0.3mm below the deck.

With a 1.0mm base packer, the piston protrudes by 0.9mm out of bore at TDC. Therefore, with a 1.00m head packer, I would achieve 0.9-1.0mm squish, still at least 0.2mm short of Malossi's recommendation.

With just the stock base gasket, the piston protrudes by 1.5mm exactly. If I went with this, I would need at least 1.8mm of head packer to achieve the recommended squish, or 1.6mm if 1.0mm SBC is the way to go.

Should the stock head have 1.0mm clearance? Do they vary? Will the compressed 'O' ring give me an extra 0.1-0.2mm of clearance?

Maybe I have a bad set of Verniers or dodgy eyesight

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Sat Mar 30, 2019 3:36 am quote
When I said measure your squish clearance, I was meaning with solder wire. Whenever measuring head, piston and gasket with verniers the number always comes out smaller than with solder wire. The solder wire test is the only one that matters.

Unfortunately all of the parts we buy vary. They need adjusting to each engine to get the best performance. If they were really bolt on anyone could do it

WDC What's the biggest tyre that goes on a 350/10 rim and doesn't rub or need an offset?
Molto Verboso
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Sat Mar 30, 2019 7:08 am quote
I had a 120/90-10 on my P215 a while back. The assembly i used was the SIP "wide tire kit". I had to grind down the web gussets on the swingarm and modify the JL "Right" exhaust bracket that bolts to the swingarm. The SIP left hand rear disc brake fit with no problems though. I recently mounted up a 120/70-11 rear on a SIP 3"x11" tubeless rim on my pink PK200. It was pretty close clearance wise to rubbing on the swingarm webbing. I think a tire any taller might just rub in it. I don't think it's too big of a deal to grind them down, but i figure i'd share my experience. My stock 200 (with a T5 4th) pulled 1st though 3rd just fine with the 120/70-11, but it was just too much rolling weight to be sucssessful. My P215 (also with a T5 4th) scoot also pulled excellent 1st though 3rd (even up hills) with that huge 120/90-10, but it couldn't even come close to winding out on a flat straightaway. I currently mounted a 110/70-11 on my stock 200. It has 95% of the looks of a huge 130/70-11, but the scoot can pull it with no problems.

Here's a sweet tire chart to play with...
https://www.tacomaworld.com/tirecalc?tires=100-90r10-130-70r11
Molto Verboso
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Sat Mar 30, 2019 12:04 pm quote
Thanks WDC. Nice link. I plan to use a 21T clutch and 68T primary gear to counter act the larger wheel and tyre. I'm not expecting any performance or weight issues so long as I get the power delivery correct with the cylinder height adjustment. I'll grind whatever I need to in order to get the fit.

I've just ordered the Jockeys wide tyre engine mounts, so once I've cut 1cm off the swingarm, there's no going back.
Molto Verboso
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Sun Mar 31, 2019 2:51 am quote
Jack, I'm thinking to settle on a 0.5mm base packer (without gasket), which will give me 183.7/126.6/28.7. I'm confident this will put the piston 1.4mm above the deck at TDC with my cylinder, so I would still need a 1.5mm head packer, or perhaps the MMW 60 stroke head, milled with an extra 1.5mm of clearance. I could use sandpaper and glass to take 0.2mm off the sealing surface if necessary, aiming for 1.1-1.2mm SBC.

Any thoughts on the power delivery of this setup and the match to my gearing and wheel choices?
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Sun Mar 31, 2019 7:43 pm quote
swa45 wrote:
Jack, I'm thinking to settle on a 0.5mm base packer (without gasket), which will give me 183.7/126.6/28.7. I'm confident this will put the piston 1.4mm above the deck at TDC with my cylinder, so I would still need a 1.5mm head packer, or perhaps the MMW 60 stroke head, milled with an extra 1.5mm of clearance. I could use sandpaper and glass to take 0.2mm off the sealing surface if necessary, aiming for 1.1-1.2mm SBC.

Any thoughts on the power delivery of this setup and the match to my gearing and wheel choices?
0.5mm is a good place to start. Should still have max power somewhere around 8000rpm. At 21/68 with a 36, its really should pull. You're going to need to adjust it at some point but this will get you run in (twice round the block?) and rough jetted.

Need to measure the squish with solder, the rest is a guide. Can't really sand a head with an O ring so much. Will need a few gasket choices. As long as the squish solder test is 1.2 or under. Think about another head in a few months. If you do get a 39mm carb, that regular Malossi head will be on the limit.
Molto Verboso
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Sun Mar 31, 2019 10:16 pm quote
Thanks Jack. I would only need to shave/sand an aftermarket head such as MMW or MRP, as the in-built 1.5mm packing would be too much. I'll see if I can get where I need with the stock head and a combination of gaskets and packers. I'll also get the solder out
Molto Verboso
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Thu Apr 04, 2019 11:17 pm quote
I have a number of cylinder height options should I need to change the power spread to suit the gearing:

1.00mm base packer (effective 0.8mm raise with no gasket) - original plan
0.5mm base packer (effective 0.3mm raise) - current plan A
0.2mm Malossi base gasket (effective 0.0mm raise) - plan B

With the 68T primary, there is a good choice of gears....20, 21, 22, 23(DRT). So long as I can make final adjustment with the clutch gear, I'll be happy.
Molto Verboso
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Fri Apr 05, 2019 1:37 pm quote
Just like London buses, three deliveries turned up today. One from SIP with some more spacers, the 2.50-10 front rim, and the Jockeys wide tyre mounts, another with the Heidi 120/70-11 tyre for the rear, and the third with the PWK 35. The tyre looks crazy big next to a 3.50-10 and the carb looks awesome.

I need to get a bit of welding done on the casing, the clutch adjuster case thread needs retapping to M6, and I need to get the 68T primary back onto the input shaft with doubled up springs and new cush plates. Otherwise, the final assembly can commence.
Molto Verboso
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Sat Apr 06, 2019 10:52 pm quote
120/70-11? Before you said 130/70-11. This makes a difference. Both great big tyres but will need different gearing to start off with. 120/70-11 could start with 22/68 & 36.

Wouldn't a helicoil work better than welding?
Molto Verboso
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Sun Apr 07, 2019 12:22 am quote
Jack, I took a steer from whodatschrome's comment about possibly needing to grind away at the casing to clear the 130 tyre. I'm also conscious of what you had said re: gearing flexibility. The gearbox already has a 36T 4th. The main thing for me is to be able to fine tune the gearing with the clutch ie. without having to go back into the main gearbox or primary.

I'll tap or helicoil the normally M5 clutch adjuster hole out to an M6 or even M8, as the existing thread is buggered. The welding is required around the hole for the exhaust bracket.
Molto Verboso
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Sun Apr 14, 2019 7:03 am quote
Found this recent video
and thought of your build.
Don't think there is much different except exhaust, between yours and our favorite Turkish scooter.
This one is a few hundred rpm quicker than mine but no reason yours shouldn't be smililar.
Molto Verboso
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Mon Apr 15, 2019 1:16 am quote
Let the fun begin...finally
Life has a habit of getting in the way, but I'm finally getting the time to make some progress. Here are the casings and the porting and matching that I've done. I used JB Weld to fill the original factory ports and then ground back using my Dremel, finishing up with a small flap wheel to smooth it all off. I took a long time to clean the ports and rough them up, prior to using the JB, taking cues from Ginch, Jack and SaFiS. Cheers all.

20190415_095826.jpg

Molto Verboso
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Thu May 30, 2019 6:35 am quote
After several false starts, it's all systems go!!
The final bit of case work will be complete tomorrow. I could not secure the clutch cable adjuster due to previous owner of the cases having threaded the f&@k out of it. I'm getting it tapped for an M6 adjuster. I've also had the 120/70 tyre mounted onto the 3.00-11" rim.

Thinking ahead, I'm going to need a starting point for the jetting and I'd like to order in a few needles and jets to get it dialled in. Can anyone suggest some likely candidates for a Keihin PWK 35 AirStriker on RD350 reeds, on a ported and matched MHR221 motor with bell crank and BGM BigBox pipe? The carb was delivered with:

Needle: DEK-48
Pilot: 48
Main: 160


This weekend is going to be fun!!
Veni, Vidi, Posti
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Thu May 30, 2019 2:39 pm quote
Vader would have been your man there. I'll go through my fb messages and see if he mentions his jetting. Remind me if I don't reply within a couple of days.
Molto Verboso
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Thu May 30, 2019 8:03 pm quote
160 and 48 are an ok place to start. As with sdjohn's 30mm, the atomiser and neeedle will be the main issue.
That DEK is probably too weak. JJK is a needle that is widely used and would seem a safe place to start. You know you will have a small fortune in parts by the time its done.
Veni, Vidi, Posti
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Fri May 31, 2019 8:00 pm quote
Jack221 wrote:
160 and 48 are an ok place to start. As with sdjohn's 30mm, the atomiser and neeedle will be the main issue.
That DEK is probably too weak. JJK is a needle that is widely used and would seem a safe place to start. You know you will have a small fortune in parts by the time its done.
I'm pretty sure that the needles are different in the up-to-30mm carbs than in the 33 and bigger. So you can't use a jjk in the 35.
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Sprint
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Fri May 31, 2019 10:40 pm quote
Ginch wrote:
Jack221 wrote:
160 and 48 are an ok place to start. As with sdjohn's 30mm, the atomiser and neeedle will be the main issue.
That DEK is probably too weak. JJK is a needle that is widely used and would seem a safe place to start. You know you will have a small fortune in parts by the time its done.
I'm pretty sure that the needles are different in the up-to-30mm carbs than in the 33 and bigger. So you can't use a jjk in the 35.
The needles are different, the ones that work best for me are CCN, CCM, CCK and other people use BGM, BGN, what I found was it was always very rich on tick over to 1/8 throttle and, a #6 slide is recommended. my set up is 48 pilot, 158 main, CCK needle and # 6 slide running a dumbo hose to frame
Molto Verboso
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Sun Jun 02, 2019 10:17 am quote
Made good progress over the weekend, but managed to mess up the clutch side oil seal installation. I've ordered a Malossi one as I always succeed with installation of those, but when using the brown viton Corteco ones, sometimes they just won't go in. I tapped too hard with the little hammer and one side of the seal got distorted.

Most of the build was standard stuff, so I won't post commentary or photos.......bearing installs, primary rebuild (new double springs), input shaft installation, gear shimming etc. However one thing that has not yet been documented in this forum is the installation of the CMD Mighty Kong. They claim it provides extra rigidity and strength to the case where the input shaft comes through. I guess this area takes a lot of lateral pressure in high power motors and it's common for the case to crack here.

I'm not convinced, but I hope it's a worthwhile upgrade. Just the crankshaft to go in now, before I bolt the cases together. Then it's time for the MHR

20190601_115145.jpg
New backplate

20190601_115215.jpg
Backplate with input shaft support

Molto Verboso
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Tue Jun 04, 2019 11:44 pm quote
Ready to install the crank. Am I right in thinking that the bell crank and big reed inlet will result in low(er) pressure at the bottom end? How will this effect the top end requirements (compression ratio, squish) and the carb jetting vs rotary and cut crank?

20190531_195041.jpg
The marks on the inner race is just residue from protection tape used on the large socket. All traces have been removed with WD-40.

Molto Verboso
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Wed Jun 05, 2019 11:04 pm quote
Bell crank complements the reeds better, both give more mid range. Some say slightly less max power, as there is less pressure for the high rpm transfer flow. With your inlet size you're not going to worry about that.

Compression and squish should be as much your happy with. For me this is 12:1 and 0.9mm. Mines been running a year now and ok so far.

Fine tuning the durations is the difficult part. I have some MHR Dremelling to do, which will suit my new exhaust. There's definately a bit more in it
Molto Verboso
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Thu Jun 06, 2019 12:44 pm quote
I should have spotted this before, but since studying FMP's video on clutch side seals, I've just realised that my cases do have the grooved seal housing. Does this mean that I have to use the rubber seal, or can I 'upgrade' to a metal one? Does this seem normal for a 1985 casing? The previous owner of the cases had used a brown Corteco metal seal.

[edit] SIP's website has two statements that seem to contradict each other on this subject. Surely a Rally motor would have the groove as it pre-dates the P2, let alone a 1985 EFL:

"The oil seals made of metal, from later PX models, can be retro-fitted to the GTR/TS/Sprint/V/Rally models motors, replacing the original rubber item. The deciding factor is whether the seat of the oil seal has a groove cut into it or not. The PX 200 crankcases produced by MALOSSI do not feature this groove, meaning they can also benefit from the use of this seal type. If this groove is present within the motor the rubber version must be used. Attention to this difference can be crucial for an oil-tight motor!"
Molto Verboso
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Thu Jun 06, 2019 7:36 pm quote
I would use a blue grooved one with 603. Or a Malossi metal one with 638.

Last edited by Jack221 on Sun Jun 23, 2019 9:25 pm; edited 1 time in total
Molto Verboso
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Mon Jun 10, 2019 3:31 am quote
Went with the blue rubber seal and 603 in the end and got it nice and flush. Having never used one of these seals, the fit and finish was actually very reassuring and satisfying, but only time will tell if the basic blue type is up to the job in a high revving motor.

Crank now installed, so I'll get the cases closed up, then it's time to work on the top end

seal.jpg

crank.jpg

Molto Verboso
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Tue Jun 11, 2019 3:18 am quote
Timings update
Got the flywheel side on and bolted. With the 0.5mm base spacer only, I am getting the following timings and will use these as the starting point. Now to find the head centring sleeves, get torqued down, then measure the squish. Should be ~1.1mm.

Screenshot 2019-06-11 at 12.11.14.png

Molto Verboso
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Tue Jun 11, 2019 6:19 am quote
Hmmm......squish = 0.85mm with solder, so probably a little tight? The question is how to get an extra 0.2mm? Use the stock base gasket under the 0.5mm spacer or use a thicker head gasket? Trouble is, head gaskets come in increments of 0.5mm, so using the next size up would mean squish = 1.35mm.
Hooked
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Tue Jun 11, 2019 12:48 pm quote
Fantastic info here.
Dont forget one of the most important things to harmonise with all your hard work
https://www.mbscooters.co.uk/info//mb-*-tech-articles/engine-tech-*-advance-boxes+282.html
Hooked
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Tue Jun 11, 2019 2:34 pm quote
swa45 wrote:
Got the flywheel side on and bolted. With the 0.5mm base spacer only, I am getting the following timings and will use these as the starting point. Now to find the head centring sleeves, get torqued down, then measure the squish. Should be ~1.1mm.
swa45 in the calculator you have entered -1,20 for PBT does this mean the piston is above the deck 1,20?
Veni, Vidi, Posti
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Tue Jun 11, 2019 2:35 pm quote
swa45 wrote:
Hmmm......squish = 0.85mm with solder, so probably a little tight? The question is how to get an extra 0.2mm? Use the stock base gasket under the 0.5mm spacer or use a thicker head gasket? Trouble is, head gaskets come in increments of 0.5mm, so using the next size up would mean squish = 1.35mm.
The standard aluminum gasket is generally 0.25mm... you probably have some kicking about you could adapt.
jimscoot wrote:
Fantastic info here.
Dont forget one of the most important things to harmonise with all your hard work
https://www.mbscooters.co.uk/info//mb-*-tech-articles/engine-tech-*-advance-boxes+282.html
Link was broken for some reason Jimscoot - https://tinyurl.com/y3r2efyb
Molto Verboso
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Tue Jun 11, 2019 7:13 pm quote
swa45 wrote:
Hmmm......squish = 0.85mm with solder, so probably a little tight? The question is how to get an extra 0.2mm? Use the stock base gasket under the 0.5mm spacer or use a thicker head gasket? Trouble is, head gaskets come in increments of 0.5mm, so using the next size up would mean squish = 1.35mm.
0.85mm is tight but not too tight. Mine is still running at 0.9mm.
If you feel you can't leave it then add 0.1mm to the base somehow. The cheap P200 ones are 0.1mm. I have a few of those in my collection of base packers. Running squish clearance more than 1.0mm is less powerful and I'm sure that it not your intention.

dsc_0507_15188.jpg
From the first page of my MHR thread

Molto Verboso
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Tue Jun 11, 2019 10:20 pm quote
I must say I'm surprised at how little squish there is. I have a 0.5mm spacer at the base and 1.5mm at the head, so in theory I should have at least 1.0mm. Could my cylinder or stroke be a little out of spec, or are my verniers getting an inaccurate reading from the solder? I'm only dry fitting at this stage, so maybe the gasket sealer will give me a precious 0.05 or so.

I've noticed that the piston ring sits very tight in the groove vs other kits that I've used and it's pretty tight. Is this typical with MHRs?
Molto Verboso
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Tue Jun 11, 2019 11:01 pm quote
hibbert wrote:
swa45 wrote:
Got the flywheel side on and bolted. With the 0.5mm base spacer only, I am getting the following timings and will use these as the starting point. Now to find the head centring sleeves, get torqued down, then measure the squish. Should be ~1.1mm.
swa45 in the calculator you have entered -1,20 for PBT does this mean the piston is above the deck 1,20?
@Hibbert, yes that's correct. The cylinder is meant for a 57mm stroke, but I'm using 60mm. In theory, the piston is 1.5mm higher at TDC, but in my case 1.7mm, so 1.2mm taking the 0.5mm base packer into account.
Molto Verboso
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Tue Jun 11, 2019 11:42 pm quote
Nothing will be out of spec but it all has tolerances. Its always difficult with squish. Whatever you measure it always ends up smaller on the solder test. 0.85mm is nice. Like you say some gasket sealer and your nearer 0.9mm. Mines been running at 0.89 for something like 4000 miles now.

MHR parts are all tight at the start, they soon loosen up once rpm begins.

Ready for a pressure test soon then?
Molto Verboso
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Location: UK (South East)
Wed Jun 12, 2019 12:07 am quote
Yep, pressure test coming soon. I'll use RTV gloop at the base, then I'll coat the head gasket with the copper spray stuff. A little tackiness will hold the gasket in the right place when I locate the head. My OCD tells me I should have bought the MRP head with the extra 1.5mm built in, instead of the thick head gasket, but the spending had to be reigned in to some extent. The base packer is a poor fit around the studs and will need a little adjustment, but from what I've read, Malossi kit installations on Piaggio 200 cases often run into stud spacing and tolerance issues.

I have just taken delivery of CR80 plates, which I will use in a SIP Sport 22T Cosa clutch that I bought last year for a different build. It's not a Superstrong, but it does have a ring around the basket, stronger centre and it's a 16 spring, albeit with only 8 XL springs installed currently.
Molto Verboso
One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
Posts: 1110
Location: UK (South East)
Wed Jun 12, 2019 12:31 am quote
jimscoot wrote:
Fantastic info here.
Dont forget one of the most important things to harmonise with all your hard work
https://www.mbscooters.co.uk/info//mb-*-tech-articles/engine-tech-*-advance-boxes+282.html
@jimscoot, I have a Kytronik available, so will use that initially. Funds permitting, I'll look at SIP Vape for next year.
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