Puch w/70cc kit runs too fast

Steve Cooper /

Got my Puch w/ newly installed Amal, 70cc cylinder-piston and biturbo running, but the engine idles so fast it's going to drive my neighbors crazy, plus it's running the rear wheel at at 10-15mph while on the center stand.

I backed the idle screw as far down as it can go, no drop in the idle speed. The mixture screw also seems to have no effect. The choke as well seems to make no difference. And there is slack in the throttle cable. Any suggestions for other steps to try?

thanks in advance,

Steve Cooper

Re: Puch w/70cc kit idles too fast

First thing... You say "newly installed Amal"... is there any possibility you have an air leak at the conection between the new carb and old manifold?

If so.. the air leak will act like a partly open throttle and the motor will rev up even though the real throttle is closed.

Start it and let it "idle" up on the stand and spray WD40 all around the carb and manifold connection and see if the idle goes down (or up)... that is your clue you have a leak.

Other than that...... Look into the carb somehow (mirror?)... to make sure that the slide (or butterfly?) is closing all the way.

Re: Puch w/70cc kit idles too fast

Steve Cooper /

the slide looks like it is a far down as it can possibly travel, there could be a possibility of a loose fit at the manifold, i didn't tightly clamp the carb down, although it's quite a tight fit. good idea about spraying to check for a leak.In the old pre-WD40 days, we'd use carb cleaner to test for manifold leaks. I'm in germany this week, will have to try your suggestions when i get back this weekend.

I have a fear that due to the tight fit of the Amal aqgainst the e3ngine's magneto housing and the straight rear facing design of the intake, the slight angle to the side of the Amal, it may be wreaking havoc with the float; there doesn't seem to be any adjustment for the float height.

Thanks for the good suggestions, looking forward to getting home now...

Steve Cooper

Re: Puch w/70cc kit idles too fast

rich king /

Thank you for the info, I too have a 70cc on my 76 Puch and it seems to idle fast. It was ok when it came back from the moped shop, but a friend "adjusted" the idle screw while the engine was hot. I need to readjust the idle screw. My question here is which of the 2 screws is the idle screw, the upper one or the lower one. Also is it better to make the adjustment on a "cold" engine or should I let it "warm up" for, say 5 min..

thanks, Rich

Re: Puch w/70cc kit idles too fast

Chris Robertson /

Always adjust the idle on a hot engine.

Chris.

Re: Puch w/70cc kit idles too fast

Steve Cooper /

I believe the idle adjustment screw is the top one, but I'm not in the US so can't check to be sure. But you can very easily determine if the top screw is the idle adjuster. Simply remove the air filter, and watch the slide when you slowly turn the top screw. If the slide moves when you turn the screw it is the idle adjustment screw.

Steve Cooper

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