Puch bogging down

I recently bought a biturbo pipe, 15mm Bing carb, performance air filter, new clutch and throttle cables; cleaned all the carbon of the head/piston, cleaned points, changed transmission fluid (type F), de-rusted/kreened the gas tank, replaced the petcock, new fuel filter and checked the timing on my 78' Puch MKII. It was running great, but now it is bogging down at low-midrange to midrange. If I barley lay on the gas it quits bogging, but barley accelerates. I barley advanced the timing, but am now running on a higher octane gasoline. Just did a plug chop and it comes out coffee brown. Is this a jetting problem (The new carb came with a *82)? Or, could I possibly need to adjust the clutch cable, since I put in a new one, or adjust the needle inside the carb that regulates midrange fuel output?

Re: Puch bogging down

1. compression. you don't mention it.

2. remove air cleaner and exhaust.

3. i believe in stock parts, no kind of tweaking.

4. a complete go-through of fuel related components.

Re: Puch bogging down

Figured it out. Yeah I did all of that, minus putting those performance parts on. I just adjusted the needle jet. I dropped the clip one notch, which raised the needle, and the bogging disappeared. Still noticed a lag at midrange, but I have heard of biturbo pipes not being good at midrange. Well, for shits and giggles I dropped the clip again to the lowest notch, and now she runs like a dream, no loss of power at all. So for all you Puch owners with biturbo pipes try dropping the clip on the needle jet a notch or two.

Re: Puch bogging down

I am having a similar problem. What do mean when you say you dropped the clip on the needle jet a notch or two. Like where is it and how do you do it. Thanks.

Re: Puch bogging down

It's in your carb. Check out this link which is a expanded view of a bing carb http://www.mopedriders.org/html/manuals/puch/sm/puchsm.htm. The jet needle is #10. There are four notches in it that an e-clip, #9, fits into, and a washer #8 on top of that. You need to pull the clip out and lower it a notch on the needle. This actually raises the needle and allows a richer mixture at the midrange. Take it one notch at a time, put it back together and take it for a spin, and see at which level it runs the best. Just loosen the screw that attaches the carb to the manifold, it's not numbered on this view but it's to the left of the #27 bolt. Then you can turn the carb toward you to get to the top two bolts #26. The top will come off along with the slide and some other parts #7-11, & #23-25. Push in on the round cylinder, #11, below the spring and the throttle cable will push out, and then can be taken out through the bigger hole. Now remove the washer out of #11, and then the e-clip and needle to adjust them. Put back together in reverse order. Don't tighten the top two screws, or the manifold screw too tight, or you could strip them. The whole thing's aluminium, so they're like spark plug threads. I screwed my old carb doing this.

Re: Puch bogging down

Patrick Mattison /

that's what those are for? hmm. i just threw the carb together and hoped it worked. i wonder if i can get better mid by playing with that. thanks.

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