803A Hits a Wall at 9.3kW

[Tinstar]

Might I suggest that you add a bit of seafoam to the oil before changing it.
It does a great job of cleaning inside the engine and hopefully freeing up piston rings.

Yes it’s safe for that, says it right on the can.
Just can’t run it forever.
I don’t remember the max amount of time it can stay in before dropping the drain plug.

If that doesn’t work, then try the methods already mentioned.

I would try all sound suggestions before tearing down the engine.

 

[cstumpf750]

The proof will be when you run it under load. If your oil pressure is higher and it will sustain a load longer than before, that’s progress. I would load it to just below the previous max and see what it does.

 

[Ray70]

Got to run it today. Definitely has blow-by. Not as much as some people have posted about on here. Not shooting oil out of the fill hole, and doesn't pop the dipstick out when running, but definitely positive pressure in the bottom end. I can feel each cylinder's compression compression stroke. It's still holding right at 20psi oil pressure.

Since I've put about 6.5hrs on it, would you suspect a full engine rebuild is needed, or just some engine restore and a couple of hours of hard running?

Haven't even begun to look in the manual for engine rebuild instructions and part numbers, so no idea the time I'd have to put into it. Only ever fully rebuilt small gas engines that can be done easily in a day.

How are you measuring the backpressure? Are you using a manometer, of judging it simply by feel?
The 803 and by far worse, the 802 can be deceiving if you just go by feel with the oil fill cap off because of the crank and pistons pulsing up and down.

To test compression I made a steel tube the shape and size of an injector that bolts right in place of an injector. It has an o-ring on the face to seal to the bottom of the injector hole and the center is threaded with a 1/4" NPT to accept any compression gage.

I have also seen the old school automotive compression testers with a rubber tip that you just push against the hole, but the gages usually won't go up to the needed 350+ PSI and I'm not sure you could old back 350 psi by hand.

 

[CallMeColt]

This seems to be exactly what mine did in this video series..... head gasket was bad. It eventually kept getting worse & ate all the coolant & blew the engine.

 

[handyjay03]

This seems to be exactly what mine did in this video series..... head gasket was bad. It eventually kept getting worse & ate all the coolant & blew the engine.

Not losing coolant or gaining oil. In fact, when I changed the oil from the previous owner, it looked well used (no burnt smell, but black). This would indicate to me that no coolant is getting into the oil. Looks like yours was smoking much more than mine, and then had the telltale white smoke. None of that.

Haven't had time to mess with it because of the holidays. I'm sort of leaning towards a combo of stuck rings and bearing clearance being the two problems with this machine.


Ray, I am not actually testing back pressure. Just putting my fingers over the oil fill port or the dipstick tube. I can feel positive pressure there

 

[CallMeColt]

Not losing coolant or gaining oil. In fact, when I changed the oil from the previous owner, it looked well used (no burnt smell, but black). This would indicate to me that no coolant is getting into the oil. Looks like yours was smoking much more than mine, and then had the telltale white smoke. None of that.

Haven't had time to mess with it because of the holidays. I'm sort of leaning towards a combo of stuck rings and bearing clearance being the two problems with this machine.


Ray, I am not actually testing back pressure. Just putting my fingers over the oil fill port or the dipstick tube. I can feel positive pressure there

That's good. The video I shared is when it was at it's worst. It was barley showing at the beginning & I suspected stuck rings. Just a suggestion!

 

[handyjay03]

That's good. The video I shared is when it was at it's worst. It was barley showing at the beginning & I suspected stuck rings. Just a suggestion!

Had some time before I picked up the kids to start working on it. Man, I feel like whoever makes 5/16" bolts had an "in" with the feds. After soaking half of the bolts, took like 30 minutes to get the top cover off and not lose any nuts. Soaked the muffler bolts with PB Blaster and plan on pulling that tomorrow so I can pull injectors and pour some seafoam in the cylinders. Will let that soak all day while I work on some cars, and get everything back together hopefully tomorrow night

 

[handyjay03]

Well, got all injectors out except the third one. Doesn't want to budge, and looks like it hasn't ever been out.

Muffler had some unburned fuel on the gasket. Injectors were full of carbon, so probably need a soak. Fuel return line going to injectors is original and broke in one spot behind the engine when I was wiggling it out of the way. One big concern I have is when I started, I unbolted the hard fuel line from the top of the valve covers. On two of the nuts, the o-ring came out intact. One, it came out in three pieces, but I had to dig the last piece out. The fourth o-ring was in a bunch of pieces, most of which went into the valve cover. I did notice it was oily by that nut before I removed it, so there's a possibility it has been damaged for a while. I guess that one is coming off (hopefully with a beautiful looking gasket). Are these just standard viton o-rings?

 

[handyjay03]

double post