Modern Vespa

Cleaned up the intake, put in Boyesen reeds to help with the intake. Already have a Mazzi crank, new bearings nd a Sito + exhaust installed. Now moving onto the DR177, it is already installed. I want to optimize it for riding a 55mph road with small hills. Going to remeasure the squish to verify what I have, want to get to 1mm. Clean up the cylinder ports, any pictures of the DR177 and what exactly I should clean up? How about optimal timings? Going to get a degree wheel also, what do I need for mounting, what’s the largest diameter that will fit?

More questions to come!!

If you can do it, try to get your port timing up to 124TD/172ED. That'd match a Polini 177. You'll probably find that's not possible without altering the ports in the cylinder. I have some blown up DR's on the shelf. I'll get some measurements and see what they might look like by default.

You'll also want to cut the bar out of the reed cage and possibly widen it. Then, blend/flow all the channels. Carb to airbox, airbox to reed block, reed block to case, cylinder ports to case. This would be the time to open it all up, too, especially the ports on the DR.

You're already into my Porting 101 thread, which covers a lot of this.

Once you have your port timings sorted and everything flowed, then you can worry about squish. I've always found that squish on the DR by default is in the neighborhood of 2.5mm by default, so be prepared either have the cylinder or head milled down, or spend some quality time lapping the head.

You're using the stock ignition, right? You'll need to adjust timing to 18 degrees BTDC, too.

Good luck!

I'm using the stock ignition for now, I cleaned up the intake path, opened it up so all the pieces flow together better, cut out the center support in the deadlock and put in Boyesen reeds. The reeds seem really stiff, but I did leave out the metal support since Boyesen says it's not needed. I would say my squish is in that 2.54 area where I measured it. I don't know what the head looks like yet, thinking of going out and taking a look and getting a few pictures of what I've got.

There was no head gasket is there supposed to be one in this setup? The base gasket is 0.25mm thick aluminum, the piston dome is above the top of the cylinder. The cylinder and piston look to be in good shape. The stroke measure around a 57mm.


Should I take off the front red line, non exhaust side, as part of the porting?

The base side red marking is what I would need to remove to match the cylinder to my case ports.

Does it do any good to open the cylinder ports beyond the hole in the piston ? If I open up the non exhaust side the port will align with the piston. If I open up the rear or exhaust side the opening would be larger than the piston hole.


The red on the front non exhaust side is what it looks like I can open up to make it line up with my Stella case.

The red on the exhaust side of the port is what would need to be removed to open it up to match my Stella case.

Random pictures

Opened up the two intake ports on the side, now they are about the same or a little bigger than the piston. Just took a look at the third port in the front. The DR port is 25mm wide factory and the case port is 20mm. Going to open it up a bit to 25mm looks like there is plenty of casing there and looking at other people who opened up their third port it shouldn't be an issue.

Working on assembling a 10.5" degree wheel so I can try and measure my exhaust port timing and anything that would be good to check while I'm not in a hurry. I need to find a port measuring for dummies video. Trying to read and watch videos to get an idea of good touring settings.

https://www.scooterhelp.com/tips/timing/timing.disc.pdf

degree wheel with only the use of a printer and some scissors to cut it out / paste it to some cardboard.

I feel like I get better accuracy from using vernier calipers, myself, but different 2-strokes for different 2-folks

yeah verniers for port timings, wheel for ignition timing

does this cylinder have 3 exhaust ports?

My $.02
I found that using the ring method he shows was the most consistent.
Gave me a level of certainty I could not achieve with other methods.
Used magnifying reading glasses - a flashlight - and a pic tool to tell when I had the ring truly flush with the top of the port - (pick tool to feel if there was any edge or if I was totally flush).
Used an old set of rings and his gluing method to hold in place when I did the grinding - really allowed .05 type accuracy I could not have managed without.
Broadly (and regularly) recommend this method having tried a range of them:

Yes, a large center one and two smaller auxiliary ports.

Opened up the two larger intake ports on the cylinder to match my LML case. Measured the smaller third intake port in the case, mine is 20mm wide, the DR177 stock port is 25mm wide, going to open up the port in the case a few mm on both sides to match. Looking at videos and pictures it shouldn't be an issues breaking out of the case side.

Christopher - one other thing I found helpful.
Use a sanding drum on your Dremel tool whenever possible - rather than a grinding burr.
It is way way more forgiving - and gives a very nice finish.
Kinda helps make it look like you know what your are doing - which in my case - I didn't.
Bought a set off amazon for all of about $10.00, that had three different sizes. Found them very helpful.

Measured up the oblong exhaust port today, measured it at 60% of the diameter, believe that is a good size. The small side ports don't have much to them.

Rough cut the openings now to get out a small stone and Dremel to clean them up. I've been looking at this video and opening up the two larger side ports. I keep losing my orientation, in the video, the more I watch it the more it looks like more than one area was built up with epoxy.

https://www.google.com/search?ei=Fy7tXZzdKNDUsAXruYyIAw&q=dr177+lml+case+porting&oq=dr177+lml+casecporting&gs_l=mobile-gws-wiz-serp.1.0.30i10.2509259.2515177..2517553...0.1..0.236.2089.0j11j2......0....1.........0i71.l4xFffq5qag

I can't get the link to work for me, the video was s freak moped in the search engine link, FMP guide in the video title.


https://m.youtube.com/watch?feature=youtu.be&v=bcki-q6ORPY







The green is the front or non exhaust side if I'm looking at it correctly.

About 35 seconds in it look like he tried opening up the side port further forward and broke through the casing and had to fix it.

About 54 seconds in the repair or build up is on the front outside and rear inside?

About 1:41 there are circles and XX, the circle area looks like it has a repair also, did he take to much off the first time? Not enough material there to open it up? What is he trying to show?

Got my flywheel stop and puller in the mail. Going to pull flywheel off tomorrow and have a look at mounting a timing wheel. What measurements should I get with my calipers? And which calculator would you recommend? Also please try and spell out measurements etc, I read some abbreviations and have no idea what they mean.

Trying to get an idea of which cylinder base gasket to get for optimal touring timing of my DR177, opened up the transfer ports on both sides and front. To be as large or larger than the engine case ports.

minus the rotary inlet timing info...
https://www.youtube.com/watch?v=MvGNkw1g6C8

http://ddog.at/stz/rechnen.php
google translate to english works fine.

https://martysgarage.info/reference/two-stroke-port-duration/

Thank you, looks like I have a bit of fun ahead of me tomorrow, I've seen that calculator before and the video helped fill in some blanks. Well see what I get for numbers.

Put my cylinder back on with rings and bolted it down with two bolts. I measured the following with no base gasket. Squish is 2.25 mm with no base of head gasket. Want to get that down to 1.0 mm. The head has a ring around it that is 2.0 mm.

Stroke 57.25 mm
Piston from top 0.0 mm ( ran a straight edge from edge of cylinder and it touches the edge of the piston minutes the bevel)
Connecting rod 105 mm
Exhaust 36.83 mm
Transfer 47.60

Calculator says

Exhaust = 162.49°
Transfer = 110.30°
Blow down = 26.09°

Now what do I want to do with my new found information?







Last edited by Christopher_55934 on Sun Dec 15, 2019 3:46 pm; edited 1 time in total

Looking at suggested timings, of 124° transfer and 172° exhaust. I saw similar timings in the video for the Polini kit. Looks like I would have to take 2mm off the top and add it back to the bottom. Will have to look into the cost of getting some material shaved off the top.

I could change to a 60mm crank also, don't really want to crack the case open at this time. Would need to add a 1.5mm packer, also.


Would still need to shave the head, to get a decent squish.

Hi Chris I don't know the answers but I am following your thread with interest and am rooting for you. Hopefully some of the resident tuners will reply with some good suggestions. I did not know the DR has the extra exhaust ports.

You're a resident tuner too now Hibbert.

Hi Chris, you seem to be on the right lines with your progress so far, which is a chunky base packer and big skim. I found getting someone to skim the head and barrel quite difficult, which made it quite expensive.
I did a summary of mine here (see Apr 23 2017):

http://modernvespa.com/forum/post2154415?highlight=#2154415

To get my 123/173/25 I used a 2.2mm base packer and a 3mm skim (1.4mm off head, 1.6mm off barrel), and still ended up with 1.35mm squish, so that could have been tighter too. I've since gone to 2mm packer and 1.15mm squish.

You give a measurement for Exhaust as 36.83mm, but none for Transfers; it is the Transfers you should use to set the base packer, and tweak (raise) the Exhaust to suit. I'd start by measuring everything again precisely, and see what base packer you need to get Transfers at 124°, what you then need to do with Exhaust, and then the squish you want will determine your skim.

I used a standard 57mm crank and did a lot of work on the casings , which I see you don't want to do yet, but with the opening up of the pad and cutting the crank I got 125/55 Inlet timing, and with big transfers, opened in casings and barrel, I ended up about 17PS/BHP – (see link above). You have a Stella that has reeds fitted? You don't want to check whether 60mm crank would make the base packer/skim situation easier because you don't want to split casings again? I think that's the situation from a quick read back.

Limiting factor of the kit was the 2mm rings on the DR Piston, so it's wise to look for an alternative, though the widely recommended GS piston with 1mm rings is expensive and never in stock anyway.

I also had trouble keeping mine cool, but that might well be because I'm heavy, and carry as many spares and tools as I can, so it's like I'm permanently two-up. It's been very reliable for a good few years since I built it in 2015 though, and I'll be reluctant to swap it out for my new BGM187-based engine that I recently finished.

I'll leave it there for now, because whatever I say will be improved upon when our proper resident tuner stops messing about with his leaky reeds, and gets back to helping all his new mates out!

I haven't read the whole thread yet, but will do if there's any need to add to it. All the best with it, I'll keep an eye and chip in if you get stuck.

Ooops fixed my other post 47.60mm.

If I take that much off the cylinder, the raised area that is currently there in the shape of a head gasket will be gone. Do you have any pictures of what your cylinder top looked like skimmed? Going to call a local cycle shop and ask about machining some off the top of the cylinder.

Anybody know what the squish band height is on this cylinder? Looking for something with a 1.0mm or preferably less. Going to ask local cycle shop about head also.


https://www.sip-scootershop.com/en/products/cylinder+head+pinasco+177+cc+_84120000

No upstand left on barrel, I took a bit off first fin too to make more of an air gap.

I changed head to Malossi Mk3 177 to get more air around/under it.

https://www.sip-scootershop.com/en/products/cylinder+head+malossi+mk+iii+_38348510

Of course, by the time you've paid for the skim, and bought a better piston and different head, you'll be wondering why you chose the DR in the first place.




Maybe the reduced gap between cylinder and head was part of the cooling problem....

.... which the Malossi head resolved

Found a local shop that specializes in small engine repair. I explained I wanted to shave a two stroke head, taking just about all the squish ring height area off and the guy knew what I was talking about. He works on snowmobiles, go karts etc. He said bring it by he may already have a fixture that would work. If it is possible for a decent price I could move the cylinder around 1mm and keep a good squish clearance also. Well see what he thinks machining will cost.

The offset spark plug vs a centered spark plug makes a one off setup for.figuring cost prohibitive. Back to getting something like a big 177 cylinder head and spacers. Wonder how the exhaust will fit if I move the cylinder up 2 mm?

Why take it from the head, take it from the top of the barrel.

The exhaust will fit but require persuasion to mount, by a bit of muscle.

I may end up going the route of barrel material removal, doing the head first to get squish down where I want it. The current head has a squish band that is over 2.5mm nothing I can do to get compression up until I get the squish band and head volume down.

Last edited by Christopher_55934 on Sun Dec 22, 2019 5:48 am; edited 1 time in total

But taking it from the top of the barrel will get your squish down and compression up, and the cut is symmetrical so your guy should be able to swing it.

I get all of that, the top edge of the piston is level with the cylinder now. I don't know that I trust taking 1.50 mm off the top of the cylinder and having the piston sticking out of the top of the cylinder 1.5 mm, and into the head 1.5 mm and having the top ring within 1.5 mm of the cylinder top.

Keeping the 57mm crankshaft for now, not.sure I want to split the case, if I didn't mind splitting the case I would go for a 60 mm crankshaft. Might save that for next winter's project when I'm a little more comfortable with this scooter and tuning it.

Using the figures from your previous posts above, to hopefully give this a push in the right direction, or at least an idea of what would be involved if you went for the Malossi (Sip #38348210) head scheme:

Sat Dec 14, 2019 2:56
“If I Measured Correctly -
Stroke 57.25 mm
Piston from top 0.0 mm ( ran a straight edge from edge of cylinder and it touches the edge of the piston minutes the bevel)
Connecting rod 105 mm
Exhaust 36.83 mm
Transfer 47.60”

Sat Dec 14, 2019 8:29
“Looking at suggested timings, of 124° transfer and 172° exhaust”

See what you'd get with a 2.4mm base gasket and a 2mm barrel skim..........?

Yeah, that gets back to a BGM 177 head. With a few spacers I can get the timings mentioned here with no machine work.

https://www.scooter-center.com/en/cylinder-head-spacer-bgm-pro-177/187-cc-vespa-px125-px150-cosa125-cosa150-gtr125-ts125-sprint-veloce-vlb1t-0150001-0.8mm-bgm1770hs08?number=BGM1770HS08

Got board sitting around the house and removed a bit of the squish band on the DR head, left 0.06mm. If my math is correct with a 1mm thick base gasket, and a 0.25mm cylinder head gasket I will end up with the specifications listed below. Squish is a little higher than I would like, won't know the exact numbers until I get gaskets and assemble it.

166.84 exhaust
116.21 intake
25.31 blow down
17cc cylinder head volume
10.97:1 static compression ratio
1.25 mm squish


Thinking about using spray copper on, copper gasket on the head. That should get my squish down to 1.00 mm. If the psi is to high or squish band to tight I'll add spacers under the cylinder. Estimating head gasket thickness from another 50 cc gasket I have laying around.

Went out this afternoon, slid the cylinder over the studs, slid the head on, didn't put on any gaskets or nuts. Pushing down on the cylinder head with one hand and rotating the flywheel with the other. The piston barely touches the cylinder head, you can feel it and see the cylinder get lifted off the engine case. Should get a squish of less then 1.0 mm with a 1.0 mm base gasket, maybe a 0.95 mm. Now I need to order one, from somewhere. Thinking I might call Gick since he puts them together he may have a spacer. Looking at Scootermercato I can't find one on the website. If I knew the factory Stella gasket thickness I would just order a couple of the rebuild kits and take out the base gaskets and trim to fit.

https://www.amazon.com/AUSTOR-Pieces-Abrasive-Buffing-Polishing/dp/B07NKRD2S4/ref=pd_cp_469_4/141-5445264-3280506?_encoding=UTF8&pd_rd_i=B07NKRD2S4&pd_rd_r=c82574d5-3a00-45f1-9378-5efbaa479341&pd_rd_w=eIQjF&pd_rd_wg=C8tYB&pf_rd_p=0e5324e1-c848-4872-bbd5-5be6baedf80e&pf_rd_r=35EQXH0WC8K5KX1WZB6A&psc=1&refRID=35EQXH0WC8K5KX1WZB6A


I'll post some pictures after I warm up a bit. I bought the Dremel version of these and used them to polish up my exhaust port and combustion chamber in my head. Unlike sandpaper they aren't as aggressive if you slip and don't gouge up the surrounding surfaces and flex to get into tight spots.

Nice and cheap. and lots of spares/options. Thanks!