800 weak spark

[stevenh]

I rebuilt the ignition on my 800 new points, condensers and coils and got timed in good by the manual. Started right up and ran good. Ran a couple fast laps around the hay field and then it developed a miss. Got back to the shop and the #1 plug was damp and is showing a weak spark. Now I’m stumped. Any suggestions. TIA

[400brian]

Here is how you narrow this down: You have two wires coming out from under the flywheel that feed the two external coils on the side of the engine.
You have a white and a red, and they connect to a white and a red. Carefully unplug them and plug them in opposite. With the spark plugs laying ontop of the engine, roll it over and note the spark you see. Is the weak side still number one, or has it switched to number two? If the weak side is still number one, the problem is external of the flywheel ( coil, plug wire, cap, or even plug ). If it switches to number two, the problem is under the flywheel.

[stevenh]

Thanks I’ll check that and see what happens

[stevenh]

So I found a few problems. When checking for spark again I was getting major spark leakage off the plug wires and through my hands to ground. So I replaced the plug wires and put new champion rn2c in it. I also took the carb off and found the silencer and the carb throat had sucked a bunch of belt dust into them. So cleaned it all and found my carb needle lever was set to high. Fixed all that and the heat shield so it was tight to keep the belt dust out. Reassembled and it fired right up and ran good. Took it out and it ran great! Once it was warmed up started pushing it harder and was running great at all speeds... then it suddenly faltered. Made it back to the shop and shut it down. Had good spark and the plugs looked good. A quick compression test and PTO side is 0! Oh no

E-clip is gone

Hammered up piston dome

Cracked skirt

[AirborneX4Special]

Ouch. Check those crank seals while you have it apart.

[Platinum_2]

Bummer. Looks like it got real lean....

[stevenh]

I am thinking it’s more of a mechanical breakdown with the piston pin walking out instead of a lean fuel problem. I replaced the crank seals before running it as this is the first winter I’ve had it and I had the carb set by the book. Unless the reeds on that side are bad. I could be wrong and I guess it doesn’t change anything now. I can tell this isn’t the first time it’s been apart also

[400brian]

There was oil in the gas, right? I have never saw such scoring on the side of a piston. Looks like some detonation going on on top of the piston as well.

The wrist pin circlip was gone, so yeah, that is a biggie, but wow!

Do both pistons look the same?

[stevenh]

The mag side piston looks normal to me. It’s slick and coated with oil film.

I haven’t got the clutch off yet to check the status of the new seal I put in there. The reeds were clean. I think the circlip jumped out of its groove and parts of it got by to the top that’s what made all the marks in the piston dome and scored up the piston and cylinder. Either that or the circlip was never installed on the last rebuild and the wrist pin walked over and scored up the sides. The wrist pin bearing had pieces of the shell broke off. The wrecked piston is OEM, the mag side is aftermarket. Anyway I am I search of a pto side cylinder for a CCW 440/22

[400brian]

OK, that side looks more typical. The circlip issue no doubt contributed to the massive failure. I would be concerned about that side of the crank as well. Like how much metal found its way into the crank.