Chain saw won't start hot

JP

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#1
I've inherited a Mcculloch Chainsaw and it starts right up cold. Simply will not start hot, so I have either to gas/oil it up while running or wait 30-40 minutes or so for it to cool down...then it starts right up again.

Ideas?
 
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#3
I second Nick's diagnosis. Run the engine until it heats up and quits. Then, check for spark when you try to start it.
 

JP

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#4
I'll check that. But...in theory...it runs fine when hot, just won't restart until it cools down. If the magneto is wonky, wouldn't it stop running or run poorly when hot?
 

JP

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#6
Starting requires a hotter spark than running I have found
Makes sense.

I really like this saw, runs and cuts like a champ otherwise. I'll look into it, thanks much.
 

billr

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#7
Try a quick blast of starting fluid. It's not the most elegant solution, but can be the most practical in a case like this.
 

jd

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#8
Test it Cold and Hot with one of these
Find a semi-dark place to do it. You can see the intensity of the spark. If it's a wide snappy blue streak cold, and narrow, quiet and yellow hot, weak coil. Breaking down from heat.
Take the saw's spark plug out so it spins fast when you pull the starter. Just keep the tester away from the spark plug hole. Fuel vapors can come out and be ignited by the spark in the tester.
Tester I pictured is from K-D for $15. I think I've seen similar ones around $5. Made mine from an old plug, a copper pipe fitting, alligator clamp and a screw.
 

JP

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#9
Dang. Nobody has a replacement magneto new. Too old, I guess. I bought a used one and will try it out today.
 

nickb2

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#11
A buddy at work the other day telling me the john deer tractor caught fire, was to far away from a water source, burnt the carb to smithereens. Found a chink carb for 46$
 

nickb2

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#15
I think I've seen similar ones around $5. Made mine from an old plug, a copper pipe fitting, alligator clamp and a screw.
I second this in a big way. Even until this day, I use this tool heavily. I think I bought it otc.

Here is a link. Thexton, probably just a branch office of otc or amazon, anyway, best tool for COP, magneto and god forbid I have still fun with distributor systems. Best tool. With the other model, it cuts out and wont really tell you if the coil can PUSH.

https://www.amazon.com/Thexton-THE404-Spark-Tester/dp/B0002STSBM