Re: Mcculloch 4hp no start

[joesnuffy]

Bills advice is dead on and should help find the issue. Please take of pics of the reed valve assembly. You have pretty much ruled out timing as your issue. You can put a bolt or screw or something into the spark plug boot or where it connects to plug to see how far you can get the spark to jump to see how far it will jump. I did read that those particular motors need a minimum of 90lbs psi compression to run but I also think 80 should be in the ballpark. Is your compression gauge accurate? Putting some gear oil into the cylinder like bill said will bump up your compression and if the motor hits a lick then you know it will need new rings. The man that taught at the night school I went to told a story of being a kid and having to put a small amount of oil into the spark plug hole to get his 2 stroke Jacobsen (i think jacobsen) to start since it didn’t have enough compression then he could mow. You could try that first since motor is still together along with how far the spark is jumping before taking reed valves off.

Once you try the oil trick to see if you can get it to hit re-check your compression with the gauge and let us know what psi is with the oil please.

Joe

ps the motor looks to be air cooled so the rings could in fact be worn out since the motor runs hotter than a water cooled engine and is mostly run in the summer months. I had a leaf blower that got like that once it would not start had fuel, spark, etc but not enough compression it needed a new ring or rings I had used it like 10 years at that point. If all else fails a person could pull the piston and carefully remove a ring and put it into cylinder and push it down like 1/2 inch using the piston and measure the gap in the rings using feeler gauges. Having said all that I still think 80psi should be good to go unless that number jumps dramatically once the oil is added thats why I would like to know what compression is after the oil is added.

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