I just remembered you talked about a 60cc kit on a Vespa? Could you describe how much of a power increase you obtained?I'm ready to mail the money for my stuff today,and I'm pretty excited about it.How long and how did you break yours in?Did your rpms increase much?Did you have to re-jet up very much?Or buy a bigger carb?Just some info. would be appreciated.That's exactly what I'm getting,a 60cc kit.It comes with intake and reed valve also.Thanks!
Don,
Sorry I took so long to respond, I haven't gotten the chance to get online today. To be specific, the Polini kit I have is 57 cc. (Bore=41mm, Stroke =43mm). This kit is bolt-on. It requires a plug that is one step colder than stock, but uses the same carb as original. Mathematically, this amounts to a 14.5% increase in power. It is noticable on hills and accelerating. When I put the stock pipe on, the rpms don't really change, but the power is better. When I put the performance pipe (expansion chamber) on, the rpms increase by perhaps 1000. You can hear a difference. I go up one jet size when I use the performance pipe, but not when I have the stock pipe on, and it seems fine. Also, with the bigger jet and perf. pipe, I run a more open airbox, although I'm not sure it is necessary. Basically, if you are not changing pipes, you probably don't need to make any major changes--perhaps just a change in jet. It will tell you which jet to use in the instructions based on your combination of pipe and cylinder kit.
Let me know how it works.
Chris
Hey,THANKS a lot,Chris! That's good info.! I wasn't particularly wanting to upgrade the exhaust,but I do need the power boost on hills.Top speed doesn't matter to me as much as good torque.But if you think I'd gain considerable power at say mid-range rpm I'd change to a performance exhaust.I should get the kit in 3 or 4 days.Would the jet be larger than a #60?Or #62?I'll appreciate any help you give me when I install that thing,but after tomorrow I'm off work for 7 days and I won't be near a computer unless I go to the library.I'm waiting to buy a computer that's not fed by phoneline but by Satellite only.They are a bit too expensive right now,but I'm hoping they come down in price.
I don't think you need the bigger pipe. Mine seems to give me better top end speed because the pipe is essentially unrestricted. To be honest, I rarely use it. I run with it on for fun on occasion, but it is pretty loud and the rpms race a lot faster. I really just needed the better torque. The kit seems to extend the power band throughout the rpm range. The Polini specs. show that this kit adds about a half horsepower overall. They rate the max rpms at 8800 (the stock kit is rated at 7800). I'm confident I hit 8800 or more with the pipe on and it is unnecessary. I prefer the low rpms. If I really wanted the pipe, I'd probably gear the hub down. The kit gives the best bang for the buck in terms of power and is adequate by itself. It added a few mph to my top end, but the exhaust restriction keeps it within reason. I'm not sure of the answer to your jet question because I don't know the stock jet for your bike. Usually it needs an increase of one or two sizes. I looked at mine this morning after posting my previous post last night and realized a slight error. I am running one jet size bigger with stock pipe and two sizes with perf. pipe. I was thinking that I was running stock jet with stock pipe, but I was wrong. I did increase it. Too much experimenting and I've already forgotten what I'm doing.
eMail me off list if you wish and I'll send my phone number if you want to call while you are away from a computer next week.
Chris
Okay,Chris! I'll be glad to get your phone no. for sure! And my standard jet was a #48 but I have a #52 in there now and my plug chop tests have been perfect,although I know the compression isn't too good right now.Still,the bike pulls along at 30mph with a 270lb.total laden weight,AND the bike is fairly heavy itself.But without the 2-speed tranny I'd be dead on the hills,and I sometimes have to put my feet down and push myself along or pedal like mad.My Minarelli Sebring is a more powerful motor but a single-speed only.I know what you're saying about forgetting while experimenting;I'm bad about not writing stuff down myself.So you think I would gain considerable power without a bi-turbo?That will suit me fine as I don't like loud noise while I'm sightseeing anyways.THANKS!
The torque increases as a result of the larger displacement. This translates into greater horsepower. You'll notice on hills and will get to top speed faster. Your top end won't change much due to exhaust restrictions, but if you don't need any more top end, why worry about it? I think the piston kit provides the best bang for the buck regarding power. If you're interested in speed, that's another story.
Chrisr
No,Chris,that sounds like just what I want.We have some NASTY hills here in southern Ohio and the bad thing is,they're usually a short-cut that will save you miles of humdrum State highway driving dodging 55+mph motorists.That's gonna improve my scenic routes dramatically,I hope.Speed is only necessary to me if I'm trying to get to a pull-off place before some reckless driver I see coming up behind me forces me to `hunt grass'.Know what I mean?Thanks for your descriptions.
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