My 520H has gone hunting - needs some help

If replacing the switch helped it may have been a weak connection in the harness or inside the switch that caused a weaker current to the coil causing a weak spark as it heated up. Is that what you're thinking also?

We have a solution for the harness side lol. Indak Electrical Parts

Yep Gene, that's what I'm thinking. It seems like something is heating up and cutting power to the coil, or maybe just coil breakdown. I'll check out your Indak parts.

I'm thinking of running some temporary wires and bypassing all the connections. I wish that Onan coil was not so hard to reach.

Kurt

I just put a jumper clip from the coil pos to the battery when I have switch problems. Just the fact that the switch helped would take me away from the coil at first thought but the jumper is a good test.

Gene, you and I were thinking alike. I ran a jumper wire from the 12+ side of the battery to the coil. I mowed with it for about 20 minutes. No change, so it is not in wiring.

I guess it could be the coil or wire, but some how I doubt that.

Not much left to try. I'm going to check for intake leaks again and check the governor settings (again). I'll check the spark too once it cools off a bit.

The good news is that even with the surging, this thing is a mowing fool. I was cutting 12" high grass at full 48" width without any problems. I guess this was the good side of the Onan's.

Thanks

Yet another update:

I mowed for about 2 hours today. The surging is getting better. I can hardly hear or feel it now, but it shows up on the vacuum gauge. I think the Sea Foam is helping. When I can easily cut 10 inch grass, things can't be too bad. A couple of weeks ago, this would have stalled the engine.

Also, I noted some vibration in the deck. I pulled the deck and checked the blades for balance. One blade was off, so I ground that into spec. Seems to be better now.

I'm not a snake oil guy, but you've gotta love Sea Foam.

Kurt

Glad things are looking better for ya Kurt!!

Hopefully it will work itself the rest of the way out. Seafoam is a miracle cure.

Yet another update.

I started mowing this morning and the surging returned. Not what I was hoping for. I changed to non-ethanol premium gas and tractor seems to run smoother, but no effect on the surging.

So, I pulled the carburetor yet again. Cleaned it as best I could. This time I ground a screwdriver to remove the main jet. This carb is pristine clean now. I was hopeful, but the surging is the same. Not terrible, but noticeable. I was bummed out a bit as I am running out of ideas.

I decided to recheck the governor settings. Following the manual, it indicated that the linkage should be one hole inboard from the center hole where it had been. So I moved it. I started the 520H and the surging was horrible - much worse. So I thought, what the heck, and moved the linkage to the outboard hole on the governor arm. Guess what, the surging is GONE.

So I am declaring victory, and retiring from the field. At least until next time.

P.S. I can now pull a 520H carb, clean it and re-intsall in about 90 minutes. Not something I really want to crow about.

Thanks for all the help.

Kurt

Victory lol.

Congratulations, tenacity wins again.