give up?, puch 2sp polini, no low, rpm related?

but there is so much more than just that to it.

this is a polini kit that was seized before i got it, honed, ran really well, but i was lazzzzy on the chamfering, and WAY lazy on fixing that even after i realized, so i then broke a ring in the kit.

smoothed it out again, chamfered a ton, probably too much in some places, there is one little discoloration of a groove left where the ring had cut into it as well.(which could be smoothed out more, but at this point i am worried about having an oblong cylinder)(would that be a HUGE problem?)

so i know there are already some of you out there who are saying its dead

but anyway, i got a new ring and put it together and its been.. spotty

worked ok, didnt work ok, i fucked with the timing, and had ONE awesome run, then decided to tweak it more, so lost that setting, but also stripped a cylinder nut during that run so now had air leak problems.

put it back together, new stud

and sometimes it runs ok, sometimes it dies on idle, i think there are no air leaks left, but the last time it was reallly leaky for some reason, everywhere killed it with carb cleaner, even after being cleaned and redone and let sit for 24 hours before final tighten or run.......(silicone)

but then there are the good times.

when i have enough speed from momentum or pedaling to get the rpms high enough, the damn thing TEARS (14 bing, proma gp pipe) then pops into second, looses rpms for a second, holds back, hits the spot again and is offffffffffffffff.

but i live in san francisco so most of the time i hit a hill, i pedal as much as i can, i get just to decent rpms, the bike kicks in, pulls me up the hill, accelerating till the 2nd speed shift, but then my rpms drop and i am dead(still running actually but no ability to move me forward respectably)

i know i know, the kit is dead, but i still want to try. it can work, i have felt it, i need to raise compression or its something i am not thinking of.. i dont know.. any suggestions? how to get to higher rpms? how to change things so the pipe kicks in sooner? the cylinder is already used, so its not like i could make things worse porting something if anyone has any ideas....

thanks!

Re: give up?, puch 2sp polini, no low, rpm related

david,

the polini's are chromed bore kits, so they can barely be honed once. the chrome is like, on the order of micrometers thick, so i'm guessing its all chewed off from the honing and the rings aren't seating. bikes with poor ring seal can still be really fast at top end. a lot of machine shops can get the cylinder sent out to be rechromed, then a new set of rings will be all you need for that polini to be better than new. you can check for sure by running a compression test, but i had a 3-wheeler that i did the same thing to, and it will only get worse as the cast-iron rings eat more aluminum away. Take it to a machine shop, it should only cost like 20 or 30 bucks, and they'll get it chromed and put a professional hone job in it. if you really want to go all out, for like 90 they'll put nikasil in it, and it will get magic-fast.

Re: give up?, puch 2sp polini, no low, rpm related

damn! good to know! i might know someone who can do it AND that is way cheaper than a new cylinder!

i figured :(

Re: give up?, puch 2sp polini, no low, rpm related

Cleats Onionpockets /

or if you want to get back your low end, just rearrange your sprocket setup. I think stock was 18x45, so drop that front one down to 16 and you will be golden.

Re: give up?, puch 2sp polini, no low, rpm related

the lower front sprocket does increase bottom end(i have a 17 to put on maybe) but what does it to to RPM? cause my main issue seems to be around that

Re: give up?, puch 2sp polini, no low, rpm related

increasing torque by changing the gear ratios would increase your engine RPM's. I keep my gearing at 11x36 for regular runs or 11x42 if I want some torque back.

Re: give up?, puch 2sp polini, no low, rpm related

🇮🇹💦 Of the Loin /

11 in the front? damn why do you need to run such a low sprocket

Re: give up?, puch 2sp polini, no low, rpm related

well it's a Sachs engine, 11 in the front is stock. good thing too because my bike weighs about 145lbs plus a 182lb rider, so hills are a bitch even with the 65cckit. max on a 30degree incline is barely 25mph :(

I bet if I put the stock pipe back on and 11x46(stock) I'd take that hill with easy.

Re: give up?, puch 2sp polini, no low, rpm related

The RPM that the engine is going to make is fixed. What the sprocket or gearing change does is it lets the engine get into it's horsepower range sooner as you ride.

If you do not care about going 50mph but want better performance on the hills of San Francisco, then go to a smaller engine sprocket.

Re: give up?, puch 2sp polini, no low, rpm related

oh? That explanation makes more sense.

Re: give up?, puch 2sp polini, no low, rpm related

🇮🇹💦 Of the Loin /

oh i thought you rocked an 11 on a puch

Re: give up?, puch 2sp polini, no low, rpm related

For a two speed you should have stock gearing of 18x40, this should give you sweet all around performance with or without a kit. If you want more low end take off go lower in the front, if you want good top end go smaller in the rear.... you want to find a good balance of both. Balance the rpm and how you want your bike to feel, it may take some dinking around. With an 18 up front though with the two speed and a polini you should have great performance.

Re: give up?, puch 2sp polini, no low, rpm related

It sounds like you have an airleak. Where are you using silicone? I don't think there is any place appropriate for silicone.

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