Polini Exhaust on Stock P200. Jetting suggestions please

I was recently received a polini exhaust as a gift. this one:http://www.sip-scootershop.com/EN/products/racing+exhaust+polini+for_20020230

I see that it mentions SIP-TIP: A larger main jet and adjusted ignition timing are absolutely necessary for optimal and reliable use of this exhaust system. 139 and 177cc setups are ideally combined with a 24mm DELLORTO SI carb., a higher ratio primary drive kit and do not forget a lighter flywheel. 200 and 220cc setups also benefit from larger diameter carbs, taller primary drives and lighter flywheels.

I am running a stock P200 with a 24/24 carb. Any suggestions as to where I might start with the up jetting?


You're welcome. If you try the polini and you are not satisfied by the performance, but you like the sound, there is a modification that make performance increase at all rews but also a bit the noise.

In the pic you can see a polini open. You have to eliminate only the first bulkhead (arrow), so you need not open all the exhaust like in the pic.


The polini exhaust does not work very well with your stock engine (in my opinion it is not very good also with tuned engines: bad at low rpm, just decent at mid and high), you risk a great disappointment. Get a sip road or a proper expansion for mid rpm.

Anyway, the only thing that you have to care about with a different exhaust on your stock engine is the main jet. If your vespa is with autolube you have a 116 min jet, if without autolube you have a 118. You need 2-4 points more (i.e 118-120 with autolube, 120-122 without, but only 2 pints more shoud be sufficient). Bye

Well in my opinion it is not convenient with the stock cylinder. The timing is set on "A" (about 23 degrees), you could set it on "IT" (about 18 degrees) or in the middle; the advantage is that the engine gets less hot and reaches more rews (but to be honest I am not sure that a stock 200cc can really take a significant advantage); the disadvantage is loss of torque at low rews.

Well, since it didn't cost me anything I have nothing to lose but time.

Thanks for the information.

Thanks again. I'll let you know how I like it.

There is also mention of advancing the timing. How crucial is this, and how much of an advance is needed?



It's been a while,

I've had the polini on for several months now. I am fairly please with it.

After several upjets I was still running very lean. I ended up needing a 126 main jet. after a lot of experimenting with jets and mixture and spending a small fortune on spark plug chops, I was finally able to dial it in, I think. If anything I am a bit rich right now.

I haven't noticed a whole lot of difference in terms of performance. Most of my riding is done in town. I was noticing a bit of bogging in the top end of the revs at first, but after getting the jetting right and warming up the engine, this is no longer a problem.

I am curious about the modification you mentioned in the previous post? Would you tell me about it, please?