Modern Vespa

The PWK is an enigma wrapped in a fortune cookie. I guess I should've known that judging by SDJohn's exploits here among others.

Haven't even gotten to the main jet yet. Things are pointing to the slide cut out but I'd like to avoid that if possible seeing as each slide costs more than what I paid for the carb itself.

Idle, 1/8, 1/4 and 1/2 throttle seem to be content individually yet incongruous together.

Setting 1/2 throttle aside and just focusing on 1/4, I've tried JJH, JJK, JJL, JJM, and JJN. All needles were set to leanest clip since I've just been focusing on idle to 1/4 throttle. All the needles worked well with PJ145 but JJN needed PJ150 and 3rd clip just to run reasonably well.

Thought JJN may be the one since it was requiring different jetting and clip position but it was always just out of tune regardless.

This is why I believe it needs a different cut out. Have done 5 needles and 10 pilot jets and 1/8 and 1/4 won't dial in together. Can sometimes get one position good but some other one will get worse.

Currently have the NAPE needle it came with back in with a PJ45 which is the pilot jet that needle liked best. Have yet to test ride but seemed good on stand. Basically just a last ditch test in the hopes that needle matches the 3.5 slide it has. If that fails to catch it's back to research.

The amount of variables this rinky dink carb has is maddening and mildly hilarious.

I have a spare cylinder head with more squish area I may try as well to rule out pinging vs fueling. I know they aren't mutually exclusive but it would be one less variable. The squish currently is 1.5mm but I'm not sure the combustion chamber is compatible. It'll start out great on the test run then run like crap after about 50 feet lately. Even after switching back to known decent jetting combos. That's why I'm suspicious of the head.

The lights are all wired up and work great. The increase in brightness alone made this swap worth it even if it never runs worth a damn again.

For reference these are the two heads I have. Currently the Polini 208 head is on it.

https://www.sip-scootershop.com/en/product/cylinder-head-mmw-px200-for-polini-208cc-for-vespa-200-rally-p200e-px200-e-lusso-98-my-cosa-200_13013975

https://www.sip-scootershop.com/en/product/cylinder-head-mmw-px200-for-malossi-210cm-old-sport-mhr-for-vespa-200-rally-p200e-px200-e-lusso-98-my-cosa-200_13013855

The NAPE needle works excellent. During the test ride from about half throttle up it was cooking! It was great! Just gotta keep ironing out the rest.

The NAPE is a double taper needle that's a mm or two longer than a J and the straight diameter is equivalent to D. I'm running it on the leanest clip with a PJ35.

I still think it needs more air on the bottom around 1/8 - 1/4 throttle. The NAPE is very skinny at the bottom so it's very rich compared to the usual 46 series needles. Still waiting on smaller pilot jets so can't test that out. Need to look into the NA series needles and see if any are leaner just on the bottom. Lastly is the slide again. I found a NOS 5 slide (bigger cut out) for $40 I'm going to try. Currently have the standard 3.5 slide. Hopefully that cleans up the bottom throttle.

Main in it now is the recommended 170 tuning jet. It's actually not far off. At WOT it's close and just a little boggy but if I pull the choke it will bog hard. Have a 168 to try out tomorrow.

Still piddling about. No parts yet to address bottom end.

WOT is flat. Have tried 170, 168, 165, and 162. There was virtually no difference between 165 and 162. There is some very slight resistance but no other symptoms. Going to try 160 and hope there is some noticeable improvement.

Things I'll be looking into are jetting, compression/chamber profile, timing, plug range and carb size.

Carb being too small was a similar issue when it had the Pinasco 177 and a 20/20. I've run into it on a couple motorcycles as well.

I'm hoping I didn't end up with a weird 2T powerband with it flying in the middle and dead on both ends. I can live with it dead on the bottom but dead on the top will be a tragedy. Anyone have a PWK30 sitting on a shelf?

Plug was too cold at WOT with the variable timing. Went one hotter and previous flat jets responded. Retested 162 and also tested 158. Both had rich and lean stutter respectively. 160 has next to no stutter.

Half tempted to try the knockoff PWK28 I have since it has a powerjet. It's so damn close but just needs a little 🤏 something. Mid range was also better with 158 so it'd allow me to step down to that. Best of both worlds in theory.

The gearing worked out well. Went with a different 2nd and 3rd vs a short 4th. Zero issues with the 3rd to 4th shift some people mention with an Old Malossi kit. Only downside is I don't think I have much more top speed than I did before. Zero to 60 is amazing though and it gets there quicker. No more needing a tail breeze going downhill.

Going to keep fiddling with the top and bottom but happy otherwise.

Kept messing around but wasn't making any progress. Still waiting on other carb tuning parts.

Decided to throw on the no name carb with the powerjet. Now have mid throttle to WOT dialed in and it RIPS! 🛵💨

NAPE on 4th clip and MJ152

Quarter throttle is still elusive. No name slide with no numbers and it's an oddball size so can't swap out.

I do have some leaner NAP* needles on the way and also a nicer aftermarket PWK28 with an adjustable powerjet. I don't trust this one for the finer adjustments down low.

Don't think top speed is going to be much higher but this thing gets up to speed QUICK! I'm rechristianing it BIG Ripper!

Sorted an idle air issue. Bad o-ring. Wanted a much smaller pilot jet after that. Cleaned up the very bottom end some. Quarter throttle is very close. Maybe one needle off.

Went for a nice long ride and it rode very nicely. Got some video and audio and working on getting that edited together.

Wasn't shooting for absolute top speed but hit 68 mph (109 kph). Maybe in the right conditions I could hit 70 mph.

The gearing is about as tall as it can possibly go to run the 8s unfortunately so no highway cruising for me.

That gearing site has to be off. According to the site I'm only hitting 6500 rpm which I find hard to believe. If I was to hit 8k it says I would be doing 80 mph. I don't think those dirtbike tachs are accurate so I doubt I'll ever know what my rpm is.

I was optimistic and hopeful, but to the surprise of no one, the nice blingy aftermarket carb with the adjustable powerjet had two major design flaws.

One was the A/F screw was set up like a fuel screw vs an air screw. Instead of a large o-ring at the threaded end it had a tiny o-ring at the tip which did nothing for an air screw. I couldn't swap to a conventional air screw either due to the surface finish of the carb.

Secondly, the tower of power, ie the jet holder, was 1 mm taller than stock so it made everything richer. Granted I could adjust the float to compensate but it wasn't worth the hassle.

So I'm back full circle running the knock off carb. I originally bought it off Marketplace before I knew about knockoffs. It says Keihin on it but it's a bit chintsy. It's got a fixed powerjet though and genuine parts fit. The Keihin slide fits as well but they're a tad loose. Not by much though. I swapped over all the Keihin parts except the slide because it has a more favorable cut out vs the standard. The cut out is narrower but taller. No numbers. Will eventually get around to ID'ing it so I know which way I went at least.

Now idle is great at 30 and 1.5, 1/2 is perfect at 4 on the NAPE, 3/4 is perfect on the NAPE double taper, and WOT is amazing at 150 with a little nudge from the powerjet. 1/4 is still a tick off but I have a couple NAP* needles on backorder.

Regardless of all the issues it flies now! Maybe I'll get into the 70s now. Going to try to get a ride vid soon.

Thanks again for the archive all the help along the way! 🏆

Did some more fine tuning. Got another mph or two. As far as performance I believe I got what I set out to do. Snapped this one while out for a test ride.

Made further tuning adjustments after finally getting the NAPF and NAPG needles off back order. Was running better than ever. Hit 67 mph and it was still pulling and I bet it could hit 70 mph but I was erring on the side of caution. Not that it mattered.

Turned onto my street to bring it in and rocks in a coffee can. Crank snapped at the clutch. Clean brake tho and luckily I was just turned onto the street and still going slow.

Guess it's back to four stroke motorcycles for a while. 😅

Had a standard version Mazzy 57mm race cut crank that came in the engine. Any suggestions for good performance 57mm rotary cranks? Might just get the heavy duty version of the current crank but more power is fine with me since I have to do it anyway.

Yikes sorry to see this. No info on a good crank, but someone will pipe up with a recommendation...

Thanks. Seems to be no other damage luckily. Looking at flowed cranks currently.

O M G!

Awful. Thought this was done. What crank was that?

Plenty of cranks to choose from. The sip ones are good for the money.
https://www.sip-scootershop.com/en/product/long-stroke-crankshaft-sip-premium-for-vespa-200-rally-vse1t-33997-p200e-px200-e-lusso-my-cosa_45021510

So sorry mate but once again, Mazzucchelli confirming their quality downhill…

Damn.
I had a mazzy crank shit the bed during the build phase on my vnb when I torqued in the flywheel. IIRC I went with a Tameni.

Correction. It was a Tameni crank that pooped the bed. Replaced with Mazzy. And it was when I was removing the flywheel to adjust timing.

Note the dark spot in the meat of the steal. Manufacturing defect.

Yeah. It was a Mazzy race cut crank. I believe the standard version. Figured if it was going to fail it would've done so already.

Been perusing SIP. Thinking flowed 57 cut crank. Going 60 will screw up my port timing. It's very nice currently. Seems to be very balanced power band. Just reading up on it for now.

Thanks. I've read about Mazzys and that problem but figured if it were to happen it would've already done so. Least it offed at slow speed and seems minimal collateral damage.

Oof! That divot looks similar to mine. There's one on the clutch side but an inverse matching protrusion on the crank side. If your's was just an air pocket that's pretty shocking. Just about the worst place for it. Sheesh

Still on the fence about 57 or 60 due to timing but saw Mazzy and Polini side by side. Both have the same inlet timing as my current crank. Mazzy looks DIY compared to the Polini. A lot less mass on the Polini as well. May give that a go if I decide to do 60.

https://www.sip-scootershop.com/en/product/long-stroke-crankshaft-sip-performance-for-vespa-200-rally-vse1t-33997-p200e-px200-e-lusso-my-cosa_45021600

I like the rod on that but don't know if I could go back to that stock timing. Kinda got used to the cut crank timing. I ended up going with the Polini 60 cut crank. Will see what port timing looks like with a 60.

Decided to give the cut Polini 60 a try just based on mass and apparent quality vs another Mazzy. Was still same price range as well. The Polini also looks like it would be easy to add a few degrees to intake if wanted.

I had the Polini, it's a nice overall crank but SIP cranks are superior (made in Italy by Primatist)…

Yeah I'm sure but compared to the same spec Mazzy it looks a lot better quality. Also balanced which the Mazzy wasn't.

The last suggested SIP crank was pushing $400. If I was going to get into the $400 range for cranks I'd just go reed. That's a whole other can of worms for some other day. 😅

I don't see any oiling holes in the top or bottom end of the polini con rod. I do know the SIP con rods have them.

That's why I mentioned I liked the rod on the one you suggested. I didn't like the timing tho. The Polini was already ordered by then. I'll have to check it out when it gets here. The Mazzy doesn't seem to have any either. Maybe it can be shipped off somewhere like Worb5 and upgraded.

Nothing seized on mine. I believe there may have been a defect or damage on the clutch side thread area from previous owners that I missed.

Got crank in. Did some measurements. Gonna be about the same with a 60.

Previous timing with 57 and 1.5 base:
In: 184
Ex: 182
T: 122
BD: 30

Projected timing with 60 and 2 base:
In: 183
Ex: 185
T: 128.5
BD: 29

Have to order a 2mm base packer. I have 0.8mm, 1mm, and 1.5mm spacers currently and tried different combos. 2mm timing from the average of 1.5mm and 2.5mm results. 2mm base spacing will give me 1.5mm squish as well with an MMW head I have.

2.5 spacer:
Ex: 187
T: 131
BD: 28

2.3 spacer:
Ex: 187
T: 130
BD: 28.5
SQ with same MMW head 1.8mm

2mm base spacer seems the best overall but 2.3 spacer looks good as well.

Break Time

Back together. Fired up pretty easy once primed. Idles and runs well.

The timings other than transfer are almost identical so it won't need much tuning. For now I went up two on the main jet to be safe and left the rest alone.

A bonus of the 60mm crank is that it will probably lean out the 1/4 throttle area to where it needs to be. Was stubbornly rich in that area with the 57mm crank. Currently no hesitation at all in that area on the stand.

Added a hardened kick sprocket and Rally kick quadrant while in there.

Weather spotty so not test riding just yet.

https://youtube.com/shorts/oazoswpLqEM?si=CD73WDfxZDUPt9oj

Sun came out and so did lil' Ripper!

It was similar but better everywhere like it's stats got turned up 15% or something. From half throttle up it sounds almost like a turbine. Dialed in two strokes just sound so precise winding up!

As far as tuning, it seemed to like the 155 main. Pulled hard but fell on it's face when I pulled the choke. Could maybe go down one but I'd like to keep it safe.

When I got back I checked the idle jet while warm and it seemed to want another two as well. Went from 45 to 50. Very snappy now and no throttle delay on the stand.

Quarter throttle, my nemesis, is slightly better but still a tad off. Mainly when I roll off to maintain legal speeds. It improves slightly with choke, so with a little more fuel I may finally have quarter sorted as well.

Thought I was almost done dialing it in... nope. This engine has no mercy for clutches. Mercy is for the weak I guess.

No damage to the crank. Starting to wonder about these cases.

Maybe I'm making too much power and it can't be contained!



Side note, I hit 69 mph on a test run right before this.

Been a while and finished a while ago as well. Went with BGM clutch components. Finished dialing in carb. Added a steering damper. Very quick and is an absolute hoot! Thanks again!

That's a very nifty damper. Where can one find it?

It's a Honda CRF dirtbike steering damper. Can buy new or find decent used ones on ebay for a little less. The mounts are from that bike as well and can be ordered from Honda. You will have to drill and tap so measure twice. If you just want a kit I saw something similar on Scooter Center's site. This is a Showa shock but the one in the kit is a knockoff.

Funcktastic! A friend of mine owns a CRF, I'll be visiting him with a box of tools while he's being distracted. 😁

Thanks 👍🏻