Pach Maxi - Carb, fuel problem

Hi everyone.

I have a 77 Puch Maxi 2hp and can't seem to keep the engine running right.

I can't get the engine to run with the air filter on. The air filter is clear and you can blow right through it with virtually no restriction. So WHY then does it run like crap with the filter on?????

Engine runs ok with the air filter off. I can reach full speed (rpm) but I have to baby it, and it takes a minute or two. I should be able to twist the throttle and have it put down the torque, but the way it is now (with the air filter off) it gives a little torque. If you open the throttle wide open it bogs down, but if you give it a little more, a little more, a little more gas as it speeds up it can get up to 30+ MPH.

These are all the things I have done wthin the last week or two regarding the fuel system (in other words, very recently):

1. New fuel line.

2. New inline fuel filter (large size, see through).

3. Complete disassembly of carb, soaked all metal parts in carb cleaner, blew out under high pressure with an air compressor, reassembly with new float bowl gasket (thick enough to avoid float getting stuck on bowl).

4. Checked to make sure exhaust system was clear.

5. New spark plug (strong spark).

6. Cleared any blockage from petcock.

Any help you can give would be greatly appreciated.

Thanks, Bill Johnson, Turlock, CA

Re: Pach Maxi - Carb, fuel problem

To simplify the reason you need to allow more air to keep it running right is that the carb is delivering too much fuel.. its running rich.

Adding air corrects the mixture.. adding air leans the mix.


This is kinda peculiar:

_reassembly with new float bowl gasket (thick enough to avoid float getting stuck on bowl_

Are you saying the float hits something if there's no gasket? Is that float installed correctly and is the bowl oriented correctly?

Re: Pach Maxi - Carb, fuel problem

Jason Luther /

is this puch new to you? was it ever running right, and then not? sounds like a carb problem.

Re: Pach Maxi - Carb, fuel problem

Brian Mikami /

I went through/did almost exactly the same things you did. Same results too. The thin (1/8") foam filter, even though it looked very pourous and see-through, had collected enough fuel/oil to restrict air. I took it off and the bike screamed to life. I'm only using 2 bug screens now instead of foam. Plug chop looks great and I'm using a 40:1 mix. Does sound like a rich issue, did you change the carb, jet or filter?

Re: Pach Maxi - Carb, fuel problem

I have a 77 Newport and went through the exact same problem... those Puchs are super sensitive to the air filter setup and if the air filter isn't right one jet size up or down will cause the thing to bog and die when you open up the throttle

First.. I'm assuming its a Bing carb in which case there shouldn't be any contact between the float and carb bowl/body with or withoug a gasket... if it's the right float it will hang freely either way.. if it's rubbing its probably sticking and flooding your carb in which case it would be obvious because it would drip like hell lol

It would help to know what size jet you have in there and the nuber on the carb for that matter...

okay.. I'm assuming it has the stock square black air filter... there is a round plug on the back of the air flter where it seats into the body of the ped... sometimes there is a snorkel type hose attached and sometimes not.. either way that doesnt affect anything... that round plug with the air inlet hole in it can be popped out to allow more air into the carb... which most people do when they upjet and add a biturbo to increase air flow..

I would suggest popping out the plug with a screwdriver and seeing if your performance improves.. if it does you are probably overjetted a tad and can either leave it out and do plug chops to nail down the right jet size or keep it in and probably downjet one or two sizes... the balance is so tricky that one size up or down will make a huge difference with the plug in or out... its just a matter of experimentation.... I tried like 30 different combinations of jets/12-15mm manifold sizes and 12-15mm carbs and finally nailed it!

I hope this helps :P

Re: Pach Maxi - Carb, fuel problem

Jason Luther /

my puch came without a filter, so i bought an after market one, so i never had a snorkle. i have made several mods to the stock set up, so what i did was drill 3 or 4 1/4'' holes in the back of the airfilter assembly. that way depending on what mods i do, i can increase or decrease the amount of air by just covering the holes with duct tape.

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