2135 issue. Overheating?

[dqdave1]

Pull the spark plug; what does it look like? White - lean; gray - normal; black - rich.
Does it have points and condensor? If it does; change points and condensor, while you are at it, change the plug. Coil is a possibility; they normally act up when they get hot.

 

[rb608]

Tonight, I made it 3 minutes before it quit. Last weekend, it ran for almost 15 minutes before giving up. If this were predictably reproducible, it would be easier.

To answer a few previous questions: It appears to be electronic ignition. No, I haven't pulled the spark plug.

I tell ya, when you first get on, it starts and runs perfectly. Then it quits when it feels like it. Because it behaves as though the timing just goes to heck all of a sudden, that at least supports the ignition module hypothesis.

The only other "new" symptom I'll offer is that #1 Son pulled the dipstick after one of these episodes, and it has a few small bubbles on it. Oil level is within the limits on the stick, but is at the high end. No clue if that's pertinent.

 

[rb608]

Since I got some good suggestions here, I thought I'd post the ultimate resolution of the saga:

I finally broke down & took it to a local shop. They let it run for an hour, but it never shut off. So the next day, they went for an hour and a half. Still fine. I suggested that it probably needed to be under a bigger load, and they should cut some grass until it quit.

That was a good idea, except that in running it so long on previous days, a hole in the muffler melted the deck belt. Okay, a few more days to get that fixed, then they were finally able to reproduce the problem.

When it quit, his first thought was ignition coil. (Everyone who suggested that was right.) But it was a bit worse than that; I had a mouse nest in behind the blower cover, and they'd chewed the insulation off of everything.

The shop pulled the engine & fixed it all. $427 (including the new belt & muffler repair.). Ouch; but I was able to cut the entire lawn at one time for the first time all year.

 

[OldMachinist]

Glad you got it all figured out.
Critters of all kinds can cause problems with air cooled engines. The best way I've found to cut down on the nests built while equipment is being stored is to cover the engine with a plastic trash bag and put a cloth bag of moth balls inside. Seems to work for rodents, spiders and wasps.

 

[diesel_nut]

I'd think when there is an over heating issue the shop would check for that FIRST!

 

[OldMachinist]

I agree, if you look at any air cooled engine troubleshooting chart for overheating the first thing on the list will be clogged cooling fins.

 

[Donsyl]

The closed in side panels dont help the overheating issue either. There is no open sides for the engine to breath. The older cubs in the 60's and 70's never really had those issues. I had a 2135 model and it overheated on me, but by then i was already so disappointed in it that i didnt care anymore. I never should have traded the 1964 model 100 that i had for it. I now have a 1988 model 1811 that i just love, but it has the closed in side panels, and the engine compartment gets hot pretty fast.

 

[rb608]

I'd think when there is an over heating issue the shop would check for that FIRST!

To be fair to them, I did not diagnose it to them as an overheating issue, I only tried to describe the symptoms. Once they were able to reproduce the problem, the fix was quick.