Author Topic: Replaced piston/cylinder now won't fire  (Read 2511 times)

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Offline sharkey

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Re: Replaced piston/cylinder now won't fire
« Reply #10 on: October 19, 2013, 06:49:03 pm »
Basically you need to find out why the cylinder failed in the first place.  Was it drawing air somewhere?  How you find out is to pressure test the case.  You can buy a pump, you can set your compressor regulator down to 5psi, or you can go up to the drug store and buy a big horse syringe.  You dont need the needle, just need the end of the plastic syringe to fit your impulse hose.  Impulse is the alternating suction and pressure wave that is piped off from below the piston crown in the crankcase, and it is used to run the carb's fuel pump. 

To do the test you will need two rubber strips.  If you have an old inner tube cut a couple strips out of it 3 inches long by an 1 1/4 wide.  Place one rubber strip between the muffler and the cylinder, and the other between the carb and the cylinder.  Bolt the carb and muffler back into place crushing the rubber strip to create a seal.

Now take your horse syringe and plug it into that impulse hose.  Put a little air pressure into the case and use some windex or soapy water to find the leaks.  Common leaks are found at the crank seals, where the cylinder bolts to the case and where the carb attaches to the intake.  Make sure the spark plug is tight.       

 

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