Series II low on power
 

The last 3-4 times I've used my 682, it seems low on power compared to normal and after 30+ minutes gets worse until it doesn't want to cut. Throttle down and it runs fine but high idle no power. Carb is adjustable and I've played with that. I figured it was a head gasket but both cylinders push 85 lbs hot. The plugs burn white and the motor has less than 500 hours on it. Points looked good this spring at least. Maybe a condenser or something? I wouldn't think governor but possible I guess? This started suddenly 3 or 4 times ago.

Is it running smoothly with no power, or does it misfire?

Runs smooth as can be, just lacks power and gets worse the longer you run it. After 30 mins or so it will start to miss a beat when pushing the hydro forward quick or something that requires sudden power until finally it doesn't want to run over half idle.
Also, I replaced all fuels lines, carb is rebuilt, and screen in the tank is clean. Symptoms are consistent every time you use it unlike a sticky exhaust valve or something. Never backfires, never dies, doesn't sputter like it isn't getting gas.

Plugged gas cap, fuel pump, something floating in the tank, vapor lock? Had the Vanguard in my 1210 start to act up the other day sort of like what is going on with yours. I could see that the filter was empty when it would do it. Pulled the tank and cleaned it even though I had done that a couple months ago. Didn't help. Screen was nice and clean, new fuel lines. Ran it without the side covers and no more problems. All I can guess is I had a vapor lock issue. Can't blame ethanol for this one because I run Shell 93 no ethanol in it and the gas was fresh. Looks like I need to insulate the fuel line. :biggrin2:

I've pretty well ruled out everything there except an outside chance the fuel pump could be going, but it still starts fine and runs smooth and never wants to die whereas a fuel pump would get weak when hot and the tractor quit. This just doesn't have the right power from the get-go and gets a little worse as you keep going until it doesn't want to pull a hill or go forward with the mower engaged unless you idle down. It never sputters like it lacks gas, just loses power. I've seen it all on these but this one has me thinking. I'm almost wondering if the timing slipped on the points or the governor gear isn't doing its job. I really hope it isn't the governor.

Does it start hard, too? Have you checked the valve lash?

I have not checked the valves. No, it doesn't start hard at all. Pretty much turn-key. Even when acting up you can fire it right up and it run normal until under a load

So did you change the coil and the condenser?Is your carb loose? Throttle cable loose?Check for any mouse house in the shrouds?just throwing out some Ideas....

It won't have mice nests in it. I've had it apart and cleaned out. Throttle cable isn't loose but I'm wondering if perhaps the linkage somewhere is binding and not allowing it to govern freely. I highly doubt coil but don't have a second one to throw on and would like to be sure before buying another just to eliminate. They aren't like the single coils when you go to buy :biggrin2: I'm thinking of throwing a condenser on it tomorrow and checking the points again just to be sure. The Mag 18 I had in my 782 was so much easier to eliminate issues with the magneto :bash2: I'm also going to take another gander at my blue ribbon service manual and see what it has to offer. My 782 actually did have a similar issue a few years ago and it was the fuel pump, but on that one it ran perfect then 20 mins later sputtered and wouldn't even start for a while. It just wouldn't work when the motor got hot.

If it runs normal till under load maybe check your pto and tensioners. When it acts up does it help to pull choke?