Havin' trouble with Puch...

Perfekt Timing Angel /

So here's the deal...I was helping a friend get his bike back together after his 70cc Airsal ate the crank bushing. We installed a new TOP crank, new main seals (we didn't touch the output seal since we didn't have the right one) and installed a new bearing on the flywheel side. The clutch side bearing had this weird bearing with a groove/lockring in it, so we pulled it from the old crank and put it on the TOP crank. He is running a DMP pipe, and a 14 Bingalingadingdong with a 92? jet. He was running this carb and pipe set-up prior to the break down and repair of this engine, and it ran beautifully.

So, we slap everything back together, the bike kicks over after about 4 kicks, idles fine. Throttle response is slow, and it lacks power, and seems to top roughly around 25mph. Currently, there is no air filter on the carb. Pulled the plug after a few minutes, it was blackity black.

So, does this sound like an overcompensated airleak, or does this sound like wayyy too rich jetting? Could the new crank have a longer or shorter stroke that may be causing the trouble?

I figured that if there was an airleak, the idle screw would not have any response when adjusted. The bike reacts to the idle screw. Thoughts? Suggestions? Thanks!

Re: Havin' trouble with Puch...

Perfekt Timing Angel /

Oh ja, forgot to mention he installed a brand new 70cc Airsal it with his set up...so yea, other than the crank, bearing, and seals, the set up did not change much from his original set-up. Thanks!

Re: Havin' trouble with Puch...

92 seems kinda big for a 70 airsal, usually on a 15 bing, those run in the low to mid 80's. the 14 will be even lower. try an 84, 82 maybe.

make sure you guys slather stuff real good when re-installing bearings, con rods, pistons, etc... thats usually why crank bushings go right after putting on a kit.

Re: Havin' trouble with Puch...

Cleats Onionpockets /

Also, make sure you check the timing.

Re: Havin' trouble with Puch...

yeah jetting is way rich girlfriend.

listen to Graham.

Re: Havin' trouble with Puch...

Perfekt Timing Angel /

Cool. We were up to 4 am working on that thing, so we didn't get to change the jetting. I just wanted to get opinions since I was afraid that we would have to rip that thing apart again.

Also, the timing was dead on before we dismantled the thing, and we both put a score mark on the stator. So, timing SHOULD be perfect/close to perfect.

His kit was running beautifully before, do you think he was compensating an airleak? The old plug was grey in color, and he claims that his tranny oil was disappearing...

Thanks for the help!

Re: Havin' trouble with Puch...

Perfekt Timing Angel /

So, tried an 82, 78, and now a 70. Still running slow/rich at low RPM's, then seems to get lean and bogs at WOT. Needle position has been tried at various notches, and the current set-up with a 70 jet, it is at the lowest notch.

Plugs aren't wet, but it is pretty black. It is an NGK B7HS. Timing is dead on.

Compression is at 130PSI. Could we still have a vac leak?? Is there anything else we might be overlooking?

Re: Havin' trouble with Puch...

sounds lean with the bog at wot. don't always judge by the plug color, it can be deceiving, especially if it hasn't been changed. judge it by how its running. was it four stroking with the 82, 78 jet? If so, I would go down from there jet by jet till is stops four stroking and and runs smooth all the way to WOT. of course check for an airleak, by spraying the intake with carb cleaner. if it dies or changes, you have an airleak. fix that first. i think a 76 might be your lucky jet.

Re: Havin' trouble with Puch...

It sounds like there was an air leak before and you fixed it. rejet, throw in a new plug and do a plug chop.

Re: Havin' trouble with Puch...

I'm running an athena 70cc with the bing 15 @ an 82 jet and I think that is a little jich

Re: Havin' trouble with Puch...

the timing could change when you put on the new crank, double check it.

Re: Havin' trouble with Puch...

Perfekt Timing Angel /

There was a tiny airleak by the intake when we first put it back together, but we fixed that. The exhaust was loose, we fixed that as well. It still isn't doing too much better.

I don't think it's an airleak on the outside, I'm concerned there is an airleak on the inside. I checked the tranny oil, it looked ok. It wasn't grey as far as I could tell.

I will double check the timing. I hope it is just that. We took the plug out of the head and did a manual test. I turned the flywheel to where the points opened, and my friend had an extension that he stuck inside the cylinder to feel for piston position. The points opened at TDC.

Bah. He really wants to take this bike to KZoo. Is anyone going who might be able to help him out in the event that he doesn't get it running? I'm trying to help him, but I'm still getting used to Puch silliness.

Re: Havin' trouble with Puch...

try advancing your timing....turn stator CCW to advance timing. point should start to open at about 2mm btdc.

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