another low compression question

[tkent02]

It wouldn't jump timing unless you turned the engine with the tensioner out. I'm curious, very odd if the valves are adjusted correctly.

Do you have access to the equipment for a leak down test?

[bobgroger]

Vince, If the petcock is leaky the cylinders could be washed down with fuel. Pull the plugs, spin it around some, squirt some oil in the cylinders and test again.

[gustovh]

Yup, I am aware of that one Bob, no gas in the oil or carb throats at the time. The tank has been off since. Going to oil up the cylinders, maybe tomorrow and see what I get.

Thought this problem was a curious one as well.
Consider that I have completed all the obvious tests, this one has me stumped because there was no warning or symptoms prior.

V

[tkent02]

The only way I know of to lose compression quickly is to burn valves, but that won't happen without the valves being too tight, and it wouldn't be all 4 cylinders so evenly.

Holing a piston is another possibility, but that would be zero compression. Curious to find out what you learn when you do the leak down test.

[gustovh]

I don't have a tester for a leak down test so I won't be able to give you any feedback on that one.

Am in the middle of a construction project at this time, so wrench time is at a premium at this time.

V

[gustovh]

Well I finally pulled the head on the engine, it is shot, the exhaust and intake cam journals are wore out, look at the #1 journal. Will try and get some measurements and post them.

[bobgroger]

I don't know, Vince. Hard to tell from the pic, but from here that doesn't look bad enough to affect the compression. But since you already have it that far, might as well pull the head and the jugs and have a look around. 16 Valve 1100 heads are in pretty high demand, might be cheaper to get a whole running bike and give me that one

[tkent02]

A little scuffing on the bearing surface has nothing to do with compression.

[JTGS850GL]

That head looks pretty normal and, as stated by tkent02, the wear on those cam journals would not effect compression. When you did the compression check, are you sure that you had the throttle held wide open the whole time? How quickly did it turn over? Did you have all the plugs out when doing it?

[gustovh]

Trust me guys the journal on #1 is SHOT. I will try and get a better close up and pics of the caps as well.

V

[tkent02]

Not saying it isn't wasted, but it could be completely eaten away, it will not effect compression if the cam is in there turning.

[gustovh]

Not saying it isn't wasted, but it could be completely eaten away, it will not effect compression if the cam is in there turning.

I agree, I am just posting what I have found. The head gasket "could have been the culprit, but that is hard to tell. More pics coming.

V

[Guest]

If I lost all compression in all 4 cylinders at once on a recently running engine I would suspect my compression tester or my technique was shot

[Big T]

Well, Gustov might be heading quickly to senility, but he's a machinist, so I trust his judgement on the cam journals. i also doubt he's forgotten how to work on bikes
So, give us some more clues

[gustovh]

If I lost all compression in all 4 cylinders at once on a recently running engine I would suspect my compression tester or my technique was shot

I used 3 different testers and got the same results. Been wrenching on bikes for quite a while and don't generally make mistakes like that. Just sayin

My best guess on the lost compression is a complete head gasket failure some how. Have not removed any valves yet to determine their health yet. There are no holes in the pistons and no sign of ring failure as well. The exhaust headers showed good burn on 2-4 and #1 running rich.

If my life settles a little I will get more and better pictures.

V