Spark plug issue?

specter22 · Apr 30, 2022

I haven’t done a LOT of work on small engines, but I haven’t seen this before - I’ve been working on a McCulloch 1-41. The saw will start right up and run… for anywhere from 1-30 seconds, then die without any hiccups. It took me a while to find the problem, but what’s happening is that what appears to be a copper ball is becoming lodged in the electrode gap in the spark plug. Each time I’ve removed the ball, and blown out the cylinder with compressed air, thinking maybe there was some debris or something causing this, but each time it comes back. What is going on?

Wood Doctor · Apr 30, 2022

Could be something in the fuel that's causing a this buildup. Also, try increasing the gap slightly to 0.025" or try yet another plug.

Pioneer · Apr 30, 2022

The last time I saw something like that was back in the 70's, lead build up caused bridging of the gap and shorted out the plug.
I'm guessing contaminated fuel or deposits in the tank. Stay away from ethanol fuel, it has a corrosive effect on some metals, brass for one example.

Chevboy0167 · May 1, 2022

I was thinking a bronze fuel filter of some sorts coming apart. Bearing cage material???

ChillyB · May 1, 2022

Describe what you are using for fuel. It’s not debris, it’s a deposit. Debris would be 1/1,000,000 chance of a tiny ball lodging in just the wrong spot even once. Every time? Nope. Has to be fuel related.