Puch won't run -- HELP!

i have a brand new carb, air filter, and spark plug. My piston is in great shape, I have compression, and I have spark. The bike ran for a day or so with all of these parts and then crapped out on me. I can turn it over but unless i continue pedaling with the clutch engaged it dies right away.

also, after this happened i decided to drain the transm. fluid and refilled it with type F (9 1/2 oz.) This made no difference except it was a tad easier to turn over. However, it is still VERY hard to turn the wheel with the clutch engaged.

I really need any help with this I can get. I don't know what else could be causing these two problems.

AIM: mayfliesarescary

e-mail: davisonj@umich.edu

or just comment here :)

Re: Puch won't run -- HELP!

you should check out fred's guide on this website


from what you say, i think that it sounds like a fuel flow problem. like maybe you have something (like rust) in the tank clogging your carb and stopping fuel flow?

also i do believe that it should be harder to pedal with the clutch engaged. this is because you're moving the engine in addition to the rest of the bike. unless you think it's harder than it should normally be.

Re: Puch won't run -- HELP!

what was the previous condition of the bike .. like why the new carb and air filter? It does seem like a fuel problem .. maybe some crap in the dirty (?) tank or fuel line is now preventing fuel flow.. Does it run if you spray some Starter Fluid into the carb's intake (or spark plug hole)?

more clues would be nice...

Re: Puch won't run -- HELP!

I took out the petcock and it was cracked in half so i ran it on reserve without the fuel filter but nothing was different. also, there wasn't any sediment in the tank. ive drained the tank a few times and it seems to be clear each time i run fuel through it.

Re: Puch won't run -- HELP!

the reason i replaced the carb was because the clamp over that elbow from the intake was busted and couldnt clamp on at all. i bought a 17mm perf. carb and then it ran really hard with the old air filter on. i took it off and it ran much better so i bought a performance air filter as well. i ordered a new petcock but i dont know that it is the problem. i pushed in the primer and gas is definately getting to the carb.

Re: Puch won't run -- HELP!

also, i know it is supposed to be hard to pedal with the clutch engaged but i can stand on the pedal and it wont budge unless i reeeaaalllyyy push it hard. i thought the trans fluid change would help but only a little.

Re: Puch won't run -- HELP!

is the difficulty with pedaling a new development? If so it could indicate mechanical troubles.. like a piston that's partially seized..

Remove the spark plug and attempt to turn the engine over.. If it's still very difficult, remove the drive belt or anything else that moves along with the crankshaft and could be causing resistance..

If the piston has difficulty moving up and down although nothing is interfering with it, it might be time to pull the head and perhaps the cylinder.. and see whats up in there.

Re: Puch won't run -- HELP!

no it isn't new. actually before the new carb and air filter it was nearly impossible to turn. we checked the piston today and it appears to be functioning well. it moves freely--no scratches or deposits on it. actually it looks quite nice for it's age.

btw, this is a puch maxi mkII sport.

im not very clear on how to work with the drive belt or crankshaft. do you know of any good guides on working with this. im very new with moped repairs.

Re: Puch won't run -- HELP!

If you don't have any Puch manual go HERE and grab one or two.. basic operation as well as tuning and adjusting things like drive belts, chains, brakes etc. will undoubtedly be covered.

If the bike ran ok although it always seemed hard to pedal, i'd rule it out as the cause of the current non-running problem for the time being..

As toonces suggested, take a look at Fred's Guide.. a thorough checkup is in order.

Re: Puch won't run -- HELP!

Smitty Smith /

Is the spark plug wet after you've tried to crank it, and pulled the plug to check for spark? This would be an indication of flooding, and would also add compression, and make it harder to pedal over.

Re: Puch won't run -- HELP!

another thought, maybe your main bearings are shot. if so it might cause the difficulty in pedaling and the engine may not produce enough power to turn the crankshaft causing it to die.

taking off the "drive belt" just means the chain that drives the wheel. you want to try to move the engine only. not the engine and the back wheel. if you take off the chain and it moves freely, then the problem is with the wheel. if it doesn't then the problem is in the motor.

Re: Puch won't run -- HELP!

I might be way off base here, but is there a chance that the entire bottom end is filled up with fuel? The piston might still move freely over most of the stroke, but could be encountering a hydraulic lock near the bottom. This would also prevent the engine from running at all.

Hydro-lock can be very strong; strong enough to pop the dome off of the piston like a bottlecap, if the engine is running. Customer had this happen on a T-500 once.. gas was pouring out of the carb, cylinder was dead, and they kept driving it till the piston flew apart.

Re: Puch won't run -- HELP!

yea there is a little oil on the plug which is new, though i still have a nice spark. what can i do about this? i doubt it's just normal flooding from trying to start it too much because i havent really done that.

Re: Puch won't run -- HELP!

hmm... i will try that out tonight (if it isn't pouring outside still). i will get back to you on that. this sounds ridiculous but where are your main bearings? the back tire?

Re: Puch won't run -- HELP!

there is fuel in the carb... it isn't leaking all over unless you push the primer in a few times. how can i check this. yesterday we took off the intake manifold and checked out the piston and no oil came out.

Re: Puch won't run -- HELP!

by bearings he means 'crank' breakings, they transfer power from the piston to the transmission.

IF and when you get the engine running you should listen for a harsh screeching sound as you gun the throttle, if you can hear that sound then replace your crank bearings. i had the same problem about a month ago and lost power

Re: Puch won't run -- HELP!

a pic of the bearings can be found on page 34 of this manual.


hope that helps.

Re: Puch won't run -- HELP!

Make sure your clutch engaging lever isn't sticking(personally I wonder if maybe you lost a clutch shoe return spring),keeping the pedals engaged and defeating the auto-clutch. Just make sure the clutch lever is releasing down on the tranny. don-ohio

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