Modern Vespa

D'oh!

Trace the base and get a spacer cut?

Grind what's not needed off the float bowl. Make some clearance in the fin. Cut a hole in the cylinder cowl. Won't cause a new problem with the carb to frame. And $0.

Zero squish head got here. Measured squish and it ended up being 1.3mm. Fine by me. Sealed it up and torqued it down.

The -1mm clutch spacer got here as well. It helped but cover and clutch are still inseparable. Spent some quality time with the dremel but still a ways off. Don't want to ruin it in the process. Going to look at covers and spacers.

Carb studs should be here soon. Looking forward to installing the carb and to start working towards installing the engine.

BGM sells a billet clutch cover if you don't want to do a spacer.

Still haven't decided on exhaust. I'm trying to split the difference between HP & TQ. Lots of conflicting info via dyno charts from different sources. Have been focused mostly on SIP Road 3.1 and Polini but have seen praises for others. The Malossi pipe, which seems to be a rebranded FACO, has some good charts and so does Megadella but they've been unresponsive so far. I can't use any big box due to 8" wheels so that rules out others I've looked at.

Anyone have any exhaust suggestions for these timings? I want to stay with a box exhaust. Carb I'm going to use is a Keihin PWK28.

Intake=184
Exhaust=182
Transfer=122
BD=30

If it not a personal question. How heavy are you?

About 200~ lbs. Not sure what that is in stones or gram crackers.

The Pinasco 177 and SIP Road 3 that's in it currently pulls perfectly fine so hopefully you aren't going to say I'm too heavy for a kitted 200. lol

In the zone for either, Polini box or 3.1. If you ride mostly at higher speed then the 3.1. If you ride around trying to stay in one gear, then the Polini.

The actual performance, even with a perfectly assembled and focused engine build, completely depends on how the carb and timing are set up.

Good to know, thanks! I'll take that into account.

Timing is just going to be whatever Parmakit says which is 18° I believe. Carb will be set to whatever performs best.

Redline is a shift point for me more often than not so I'll probably go for a higher redline box. Not that I have anything to compare it to but I've liked the SIP 3 that's on it now.

Thought this was a Malossi? With custom port timing and a different head the specified kit timing may no longer be ideal. Although, 18 degrees is never that far out.
If only carb settings were that easy. What performs the best is often too lean for long term road use. Work down from where you're absolutely sure it's rich to where it's not too rich, for each adjusted carb component and all will be fine.

I used to think, nice simple Vespa scoot. My eyes have been opened, these motor builds I have been reading about are ! Great job with the build, looking like you will be enjoying the fruits of your labor soon.

Parmakit is the ignition. Was my understanding it's one of the first ones to come out. I'll adjust the timing if it needs to be. The CDI has variable timing. Seems people think these are voodoo or something. I may switch to a CDI with a fixed curve.

Wasn't expecting that. Variable ignition is better for any 2 stroke, even bone stock. Initial setup is fairly straightforward but pragmatism is required for the finer adjustment. A good feel for the engine makes all the difference.

That's good to hear. I'll stay the course with the current CDI. I figured it would be better since it retards the timing. Not like it advances it.

I'm trying to find some original instructions for it so I can be sure to set it as recommended. Also want to see the wiring. Nothing's turning up though. Pretty surprising.

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It's probably no different than wiring up a Vespatronic ignition.

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Motor is together. Mocked it up. Had to get a few fasteners here and there.

When testing after assembly, neutral was notchy and it would sometimes jump into gear. After researching it I opted to replace the selector box with a new one based on the motor's history. NeutraI is now smooth and it shifts very well. I also picked a selector box that doesn't have the neutral switch fitting.

Got the billet clutch cover installed. Very nice bit of kit as some say.

The wiring off the ignition is borderline hacky. Should be interesting sorting it out.

That clutch cover does look pretty darn trick! My T5 currently has a spacer under the stock clutch cover. I've love to ditch that setup and get a billet version for that scooter.

That clutch cover does look pretty darn trick!

Barber is definitely worth the trip. They had a pretty good scooter display when I last visited in 2019 for Barber Small Bore.

registered user: Netweasel
Tue Jun 09, 2015 3:40 am

Here is a PWK how-to I posted on the LCUSA forum:

I recently picked up a GP200 that had a OKO/PWK 30mm fitted with an old PM Style [redacted] pipe. Although it ran, it was jetted poorly, not to mention that whoever last rebuilt the carb stripped most of the housing and jet threads. So I picked up a few 30mm powerjet OKO/KOSO/PWK carbs cheap off of ebay and decided to try various setups until I had it jetted perfectly.

These carbs seem to come from various manufacturing facilities. There are 5 modifications that you must perform.
1). Check and drill the float needle area to 5mm. (The large area of the brass insert. Be careful, and go slow. If you mess up you can pull out the brass insert, or drill through the bottom of the brass insert.)
2). Check and drill the float needle center fuel inlet to 2.5mm. (The small area of the brass insert.)
3). Check and drill the float needle area horizontal feeder holes to 2mm.
4). Check and drill the idle/slow jet outlet in the venturi to 1.2mm. To do this you will need to first unscrew the jet holder from the bottom of the carb. Start at .5mm or .6mm and work your way up to 1.2mm
5). If the OKO/KOSO/PWK carb you have uses round jets, swap out the atomizer/diffuser for a Keihin style hex jet one.

One of the main problems people encounter with these carbs is that they can't get them to idle without turning the idle adjuster all the way in. This issue is because of two reasons:
1). The first is that the idle circuit needs to be drilled out.
2). The second is that people are running way too lean idle jets. People always think that if it is lean it will cause the engine to race, which is true for main jets and slightly smaller than required idle/slow jets, but if you don't give it enough fuel to begin with it will not run at all and will mimic a too-rich condition at idle. To compensate for the too lean idle jet, people turn the idle adjuster all the way in which uses the slide cutaway to add more fuel allowing it to somewhat idle at a higher rev. Another side effect of a way too small idle/slow jet is that it will idle with the choke on.

The jetting I used was:

slow/idle jet: 48
slide: stock 3.5
needle: JJH
needle position: 3
main jet: 125
air mixture screw: 1.5 turns out
filter: stock air bellow w/ oiled foam UNI pod filter.

I used a set of Dormer metric drill bits for the 2, 2.5, and 5mm holes, and the Harbor Freight micro drill bit set for the 1.2 mm hole.

At WOT I can see the Powerjet being utilized. There are no flat spots, and the throttle response is crisp. The plug is a nice chocolate brown. I did these mods to three individual carbs, and they all respond the same on the scooter.