Puch Magnum MKII gasket leak?

I've got a nice '72 Magnum MKII that I just got running. When I go to revv it up it dies unless I almost completely cover the intake on the carb, and when I do that it runs fine. It also makes a small really high pitched hissing sound when it's just above an idle. Could this be the base gasket? I know that it's ripped, so would this be the cause? Or maybe the intake gasket? I've run puch 1 speed motors with no base gasket and there was absolutley no problem, but maybe this needs to be sealed up really well?

If I have to make a gasked, would a few layers of aluminum foil work well? Or should I get some of that liquid gasket stuff?

Re: Puch Magnum MKII gasket leak?

See Ya Moped Army /

Replace the base gasket with the "correct" Puch gasket for your motor. Base gaskets are made of paper, not foil. Head gaskets are made of foil. If it's a Hi-Torque motor, you don't need a head gasket. NEVER use liquid gasket as a base gasket. I would also replace the intake gasket as well.

Re: Puch Magnum MKII gasket leak?

covering the air intake restricts air. This forces the air:fuel mixture ratio to be more rich .. something the carb should be doing without your help. So, it could be assumed the carb is having trouble delivering enough fuel... you'd trace fuel flow and find the retriction.

but since you've other issues, the fault could be elsewhere.

A 2-stroke's crankcase takes part in the engine's pumping action.. Mixture is pulled into the crankcase and is then forced up above the piston.

If the cylinder base (or intake manifold) has a leak, fresh air could be sucked into the crankcase through the leak. This fresh air would upset the air:fuel mixture that came in through the carburetor. This extra air would lean the mixture. (too much air for the amount of fuel)

Choking off some air at the carb may artificially correct the problem.

Consider yourself fortunate just to be aware of a problem like a torn gasket .. don't ignore it or try to work around it. Fix the things that you discover to be wrong as you go along.. Replace or repair that gasket. They are easy to cut from gasket paper.

I wouldn't be suprised if the hissing noise along with the carb metering problem were both cured.

To test for leaks, get a can of Starter Fluid and spray the area.. if this affects engine speed, there' a leak.

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