Modern Vespa

Starting this thread to document (and inevitably ask for help) in building my LML VMC187 Crono race bike. The build spec will be as follows:

VMC 187 crono top end
Sip 60mm toothed crank
VMC 10molle toothed clutch
68/21 stock Stella gearing
Mrp reed intake
SIP reed block
Vape variable ignition

-If anyone wants to chime in on what carb to use, I was planning on a phbh30. -The exhaust I was thinking was the racing SIP performance 2.0 right hand expansion chamber exhaust, mostly due to the large frame Indonesian racers all using right hand expansion exhausts, so clearance must not be an issue? Assuming you'd hit selector box before exhaust, but Open to suggestions.
-used stock Stella gearing to have as much acceleration, top speed not too important for the track, open to gearing suggestions though.

To make things worse for myself, this is my first full motor build, so doing everything with no real blue print will be…interesting. Hope yall enjoy, appreciate the help along the way.

Is that a full circle crank? Inlet doesn't look like it's opened out? Assuming it is and it isn't. Not the ideal recipe for the fastest.

It's this crank. I was having such a hard time figuring out what one would be best, I kept reading conflicting things and differences between reed and rotary. This was the one that was recommended specifically for this top end.

https://www.sip-scootershop.com/en/product/long-stroke-crankshaft-sip-premium-for-vespa-125-gtr-2-ts-2-150-sprint-v-2-super-2-p125-150x-px125-150-e-lusso-my-cosa_45021530

If this engine is going into a true track bike for racing, then a close ratio transmission would be an absolute game changer for acceleration. Use a looong 1st, long 2nd, standard 3rd, and short 4th. Pair it with a correct toothed primary gear. Of course you'll rebuild the cush drive gear with new reinforced springs while you're in there.

Option 2, just use your existing transmission gearing for a full race season. If at the end of the season you want to be more competitive, then switch to a close ratio transmission at that point.

I guess it's worth noting, my previous "race bike" was a bolt on malossi 177 with a stock mazzy crank and a si20/20 carb and a road 2 exhaust lightened flywheel. That's it. And with that set up I haven't lost a race yet against built p200's and built small frames. (Sure there is operator factor as well). So I'm just hoping this build to be even powerful/more able to be beat on than the malossi bolt on build. This is also I guess just gonna be a bolt on build as I don't plan on doing any more dremeling. And for this season I'm going to run the stock gearing before spending a couple hundred on another gearbox. Budget is pretty small now after all the other stuff.

It's going to run ok but there will be a lot of metal in the way of the inlet flow. These cranks are the best for power in when the reed inlet is direct into the cylinder.

Slip the flyside case on. Turn the big end to the inlet hole (middle of the intake duration). Take a picture down the inlet. Let's see how it looks.

Okay will do tomorrow when I get back in the garage. I know there will be some things I'm gonna have to skip on like measuring timing and opening ports etc as that's just beyond my skillset. The cases are already grinded out as big as the cylinder gasket by previous owner so that's pretty much as far as I'll go with the grinder (for this build). And I'm stuck with this crank as I'm not buying another one, not till this motor blows up anyway.

You probably won't need to dremel the cylinder at all, just use appropriate packers top and bottom to reach the best port timing you can. Jack can advise on that.
Also, if you can take any kind of measurement, you can measure port timing. It's not hard, it's just following the right method.

Sounds like fun!

What type of tracks do you use? I found on a kart track with tight low-speed corners, scraping the selector was almost inevitable unless you push the scooter more upright and hang off the side.

There's only one right turn anyways Good luck with the build!!

If your beating tuned and built up PX200's and small frames, on your "Basic builds" then I'm all ears and no one here is going to give you any tips or tricks to better your endeavours. Your obviously very experienced and the so called experts here with constant misguided and contradictive information, could learn a trick or two.

Rage welding. I feel like i have seen these cases before online?

Haha the previous owner said you were the one that welded them. I wasn't 100% sure if I had that info correct so I didn't want to make a false claim.

I didn't mean what I said to come across as arrogant, and I also said that there's a lot of rider factor there with my racing experience, not specifically based on engine builds. I'm here to learn since i have very little wrenching, let alone tuning, experience.

I absolutely did NOT weld those.

So I was told/heard wrong. Glad I didn't initially make that mistake! These cases were listed online in Staten Island for months, maybe even over a year with a complete stella.

I guess I'm flattered?

A lot of that is unnecessary. Below is what I crank out. What does the gasket surface look like?

Here are some photos, if I interpreted what you said correctly. Today in the garage didn't get much progress on the motor. Just put in new kick start rubbers and made a backing plate for where the electric start was. Need to figure out how to mount the vape ignition coil, I remember another thread where someone just drilled into the case and made a little bracket and bolted it right on.

I didn't take a photo but it's machined flat, looks fine to me.

A flowed or bell crank would have been better than what you've got, but you'll have to decide how much you care about that for now.

You can probably sell that crank without losing your shirt if you want to, too. Which exact pipe are you looking at?

And the close ratio gears like whodat suggested would be ideal, for sure.

The close ratio gears will come next year when the budget renews itself. I blew it with the crank, but at this point unless anyone reading this wants to buy it off me in the next 2 weeks, it'll just have to do. Chalk that one up to learning experience. The pipe I'm planning on running (haven't bought yet and open to suggestions) is :
https://www.sip-scootershop.com/en/product/racing-exhaust-sip-performance-20-for-vespa-p80-150x-px80-150-e-lusso-98-my-cosa-1_20120CA?usrc=Racing%20Exhaust%20SIP%20Performance%202.0

just wondering if i repaired the cylinder gasket surface and milled it. yeah, i did not weld the side of that thang. LOL.

These are getting great reviews. Not sure if it scrapes any more or less than the SIP/JL.

https://www.sip-scootershop.com/en/product/racing-exhaust-sip-performance-r-t-25-design-by-nordspeed-for-vespa-200-rally-p200e-px200-e-lusso-94-cosa-1-200_2000250C

There is scope to do some work on the case and avoid buying a new crank. And allow Mr. Gick to show some more of his skills perhaps?
This guy did the work below pre-covid and achieved some nice results. He moved a case stud to allow excellent flow below the LML reed mount. Ran it for a couple of years at least like this from memory so didn't appear to lose strength. Alternatively I would think you could leave the stud in place... a port divider in a cylinder doesn't create too many problems for flow, the stud may not either.

Apparently the setup in the dyno is Crono cylinder (I think with unaltered port timings) on his LML case with PHBH 30, RD350 reed with intake manifold angled to shoot the gas flow exactly between the crank halves. Pipe was Megadella XL.

Very interesting reading. https://www.facebook.com/search/top?q=preparazione%20vespa%20px%20lml%20star

That crank has some cut out, so not as bad as first thought. It would be ok. Modifications of the type in Ginch's post are ideal. Can do a mild version of the same quite easily. Open the inlet at the front, as far as possible without moving the stud. Smooth and round the rough edges on the crankshaft where the flow enters. Make sure the manifold matches the port when bolted on. Dremel as necessary.

Next dilemma is setting up the cylinder. If not doing cylinder timing adjustment. This being a race bike, two conflicting things need to be true. The cylinder should be set as high as possible on the base. And the squish clearance should be as tight as possible, something near 0.8mm. How does it measure up on the dry fit with the piston attached?

I read somewhere that a guy was racing large built up 200's and small frames. On a basic 177 and Si20/20 carb.
I would get to know that guy and find out he's secrets. Not sure how long he's been racing but he hasn't lost a race yet.
I was really impressed. I'm going back to basics.

When I rebuilt my 177 to a 187 using the Polini cast iron cylinder, I used a stock type long stroke crank. I don't know whether a flowed or bell crank would have been a better choice especially considering the restrictive Stella reed.

You have a few options with the Stella reed. The most common modifications if you want to keep the SI carb are to cut out the center bar and open up the reed block itself by reducing the width of the edges. You'll have to drop in a fiberglass reed at that point, but you would want to do that anyway.

The one thing to be aware of is that the autolube reed blocks seem to be unobtanium, so be sure you have a spare on hand if you're not 100% certain you're in for the long haul on that mod.

My first tuning efforts on a Stella, I ran mine with the modified reed block, 24/24, flowed 57mm crank, DR 180, and a SIP Road exhaust. That put out about 15-16 HP per GSF Dyno, but not a lot of top speed (I blame the DR).

With a better top end and 60mm crank, I see no reason that setup wouldn't get you up in the 19-20HP range.

Take a look at a BGM177 for the top end. It's cheap and has a deeply inset head, like 3.5mm, so you potentially have loads of room for getting port timing and squish dialed in just how you like it (I had that .8mm squish on my GL motor and still used a .5mm head spacer). It's also torque-y as hell with an immensely wide power band, but still will happily run up to 75+ MPH on stock gearing if you want to.

I GSF-Dyno'ed the SprintV's motor at 18 HP a while back, and that's with a RoadXL, so throw a race pipe on and you're over 20 HP.

It goes pretty good with the VMC kit. Opening up the reed block helped a lot and wasn't hard to do. Sounds like the BGM kit tends to work better with the Stella reed. I have no idea what the power output is. Since it will end up in my VBB, I will probably be changing the primary since I'm keeping it on 8's.

I think the OP made a good choice by going with a side draft carb for his application. Probably more flexibility for tuning than with the SI. Last thing I was working on was jetting out a flat spot at mid range. But not critical for an open road going bike.

I missed that he's going side draft. In that case, get an RD350 block and let that puppy BREATHE!

Yeah, I'm thinking he will be way ahead that way. The Si can be made to work with a 187 and Stella reed, but my impression is that it is harder. Also from reading up on it, the BGM kit seems to work better with the Stella reed…or at least people have had an easier time setting it up compared to the VMC. The loss of autolube seems like a small price to pay though, especially on a track bike.

Yeah I already have the sip version of the rd350 reeds and already have the VMC187 top end. Haven't bought the carb yet, was thinking a phbh30 since thats what I have on another scooter, and would be nice to just keep some unformity in the garage. I barely have a grasp on tuning SI carbs, so Im sure I will have a hell of a time tuning a side draft. Everyone says they're easier, but the more I read about them the more I get confused/intimidated. I just finished rebuilding my daily p200 motor over the Christmas break (malossi 210, new mazzy 57mm crank) so now that I have that squared away, Ill be able to hopefully get this LML motor atleast sealed up and maybe squish/top end figured out next week. Ill take photos and post an update for you guys once i get on it. You truly have no idea how grateful I am for your guys feedback and knowledge.

Watch this series of 3 videos, some extremely useful info (if slightly long-winded). https://youtu.be/mJLO9R6bG4I?si=q1eGq0JJCF7FpJot

?si=q1eGq0JJCF7FpJot

Guess it's about time for me to chime in about GEARING...
Save your $$$ & get a 2nd hand exhaust (someone here will have something appropriate.
Consider their advice on changing crank.
Spend ya $$$ on GEARING...
3 items required... Long primary, long 2nd, very short 4th.

Here is a bit on the topic:
modify VBC1. 2-port - Fuel... Gimme MORE FUEL ! (Page 2)?highlight=fast+vbc

Finally was able to make some progress, lots of little things holding up any forward movement on the motor. Today I got the rear brake assembly all put together, cases put together, motor bushings in (I shoulda went klauss but I'm trying to pinch Pennie's now that I'm grossly over budget). Got the clutch and clutch cover all sorted, wasn't sure if I 'needed' to grind the cover for the VMC Molle clutch, since my last cover was already grinded when I installed my other Molle clutch, but I went ahead and did it anyway. When I put it all together I noticed there was hardly any play in the clutch arm. I took off the cover, reinstalled with a glob of grease on the plunger and didn't touch the arm, then took the cover back off and sure enough it was touching. I installed the old/normal style pressure plate (instead of the fun little spinny one vmc provides) and now I have seemingly the right amount of free play in the clutch arm. Oh well.

Then I moved onto figuring out the squish, there were lots of gaskets provided with the VMC CRONO top end, a green, black, and then 3 tan ones. I tried the green, the thinnest tan, and the black one together and got a surprisingly low number of roughly .6mm. And the measurement of the remaining two gaskets was roughly .6 which would put me just barely at the recommended squish of 1-1.2. Weird to have to use all 5 gaskets provided. I had to leave before I could try the others, so I won't really know till I give it a proper install and measurement. I also found it kind of crazy how low of torque the head bolts require. 10nm (7-8ft lbs) which is odd to me. Even though there are like 8? Head bolts, still seems kinda low.

Does anyone have any experience with using those fixed quick throttle tubes that you install traditional motorcycle throttles on? I'm planning on going that route so I can actually have a proper quick throttle for the phbh carb.

I've installed two different MX throttle tubes on PX style scooters (i used a Magura). I found that the stock throttle tube works just as well and is easier to set up. Perhaps there's a PX quick action throttle pulley that SIP sells? https://www.sip-scootershop.com/en/product/throttle-pulley-steering-head-sip-quick-throttle-disc-139797-for-vespa-pk50-125-s-ss-lusso-xl-ets-rush-n-px80-200-pe-lusso-98-my-11-t5_13978730?cr=e993ab67-6807-4109-bbed-f6374ebf9f9b&gad_source=1&gbraid=0AAAAADw9MG7iHIfiMFnC3gqG9TAc9Pss2&gclid=CjwKCAiAhP67BhAVEiwA2E_9gxV2ugzEt77LLq_P6CcbX5msUEWwRHQoxSOyQqBGpUWKut-rLtGkVhoCdkwQAvD_BwE I still like the factory plastic throttle pulley the best. The throttle cable will last longer with plastic (vs the SIP aluminum).

And the way you're checking the squish is inaccurate. Don't have 3 different points of squish with your solder. The piston will rock in the bore and will give an inaccurate measurement (just like you posted up in your pic). Just use two points for squish. Place the solder on the piston directly above and inline with the wrist pin. That will give you an accurate squish. Any other placement of the solder and it will be inaccurate.

I have also used a few different mx throttles on various scoots. Currently I'm using this throttle pulley above, and am very happy with it. Fits within the headset, and allows the PHBH 30mm carb to open fully.

One thing I dont like about the exterior mounted mx style quick throttles is that they push the throttle grip further out from center, some by an 1"-1.5". It will also require a much longer cable, and that will need to be routed outside the headset to reach the throttle, which may require drilling or cutting of the headset. Something to be aware of.

Ugh thats so annoying.

2nd whodatschrome regarding squish. The left leg of your upside-down U is the one in the best position. Cut solder the width of the bore and place it directly above the piston pin. Remeasure and see how squish is now.

If I remember right, EP got a VMC for his smallie and had the same problem. I'm not sure if he was able to fix it.

Try all the gaskets or a combo and see if that gets recommended squish. Then take measurements between top of cyl to top of piston at TDC, top of transfers, and top of exhaust opening to get some rough durations from the online calcs. Post results here for peeps to chime in.

I only measured squish that way cause I saw a bunch of two stroke dirtbike guys measuring it that way. The straight line directly above the wrist pin makes most sense to me as well. I'll remeasure with same set of gaskets and see where I'm at. Still kind of concerning to use 5 damn gaskets, all I can think about is an air leak. Anyone ever have to use so many?

don't use 5 gaskets. get a base packer of the right thickness from sip and then use sealant. 5 is asking for trouble.

I completely forgot about the MX tube being further out on the left side bar. I ended up extending my clutch side tube the same amount (by way of a welder) so that the bars would be equidistant. MX tube definitely isn't plug and play.

Agreed. My personal standard is two base gaskets max.