GX 270 low compression, oil consumption

[mark123]

I have a Honda GX 270 which will run but is very hard to start. It consumes a lot of oil and only has 50 PSI compression. There are approx 10 000 hours on it so I decided I would replace the rings and head gasket. I opened it today and the head gasket looks OK, I took the top ring off and placed it in the cylinder approx 1" down and it only has 0.021" end gap, does this mean the ring is not worn very much. There is a tiny bit of scuffing between the piston skirt and deep down in the cylinder but this area is not where the rings touch. Another thing I noticed was that the top 2 rings's gap where aligned, I assume they should be opposite each other, but thre is no pin to stop them from rotating, should there be? What else can I check that would caue poor compression and oil consumption? It always had 100 synthetic oil in it and changed frequently.

 

[OzFab]

Have you checked the valves?

Just because a head gasket looks ok doesn't always mean it is ok.

Now that you have them, go ahead & change the rings a gasket anyway but, also, lap the valves just to make sure they're ok; maybe even do a leak test first...

 

[KartFab]

Yea its probably time to get a new one, just send the old one to my home address... I'll even pay shipping to keep that oversize paperweight from burdening you with its problems.

 

[r_chez_08]

I would check that the bore is still round and within spec, if not get it straight honed and put an oversized piston and rings.
With 10k hours I would lap the valves and give the motor a thorough inspection of all mating/wearing parts. Oh and with parts like the head gasket it is not really worth reusing them, just replace them and have the peace of mind that they are not the issue anymore.

I'll look for the rings end gap and piston bore spec if I can find it.
Edit: may be some useful specs here http://cssportal.css-club.net/honda/PowerProducts/

 

[devino246]

You should have done some investigative work before you pulled the motor apart. A dry compression test (you need to spin the engine backwards to defeat the compression release and achieve accurate readings), followed by a wet compression test would have told you the condition of the rings.

You're only looking at the compression rings, which wouldn't have anything to do with the engine burning oil. Your compression reading is useless unless you defeated the compression release, do you're basically blindly trying to diagnose the problem.

Since the engine has such high hours, and you've already got it apart, check all the measurements that r_chez_08 referred to. If they check out, go ahead and do a full rebuild. Disassemble the engine, hone the cylinder, install new rings, lap the valves, and put the engine back together with new gaskets.

 

[mark123]

What should compression be?

The exhaust valve was pitted/corroded so I took it to be refaced and they did both for 10 bucks. I then lapped them and honed the cylinder. It is now showing 110 psi with the new rings, and is running good what should the compression be? Something got screwed up with the govenor I think because now it wants to run wide open all the time. With 10000 hrs it is not worth putting a lot of money into but I got the rings and head gasket sent from China for $10.00. So far it hasn't cost too much.

 

[Doc Sprocket]

Since you had the engine apart, ensure that you connected the governor linkages properly. If that's all good, adjust the governor. If that doesn't do it, you'll have to open the engine up and see what's amiss with the governor gear and flyweight assembly.

 

[OzFab]

110psi is a great deal better than 50...

Specs say it should be somewhere around 100psi +/- 20psi so, you're well within specs

 

[mark123]

The little top hat shaped thing fell off the govenor upon reassemble and thus the gov. was not doing it's job. Everything is working great now except there is a miss, could a bad coil do this or do they usually work or not work. Mine is very rusty, to the point it is literally falling apart.