How do my compression numbers look?

[Tofuball]

Hello!

I don't really have much power, so I was planning on rebuilding the carbs. Before I set to work on that, I did a compression test.


This is on my 82 GS850L, and the numbers were pretty strange. I was wondering if I could get some input on what they might mean for this engine, and what you guys recommend I should do to fix it.

Thus, if it is rebuild time, should I bother or just get another bike for the money?

CYLINDER | . 1 . | . 2 . | . 3 . | . 4
NO OIL . . | 120 | 118. | 085. | 142
OILED. . . | 148. | 141. | 133. | 165

[chef1366]

Did you do this test on a warm engine and the throttle wide open?

[Tofuball]

Did you do this test on a warm engine and the throttle wide open?

Yes, and yes

[chef1366]

Has this bike been run on a regular basis? Has it sat for any amount of time recently? If it has the rings might need some time to reseat. If not it looks like your rings need replaced on #3. Seems odd to have such a difference in wear.

[Tofuball]

Hmm, yes, it sat outside for a year, but I've ridden it about 100 miles since.

Could it still just need to be ridden?

[salty_monk]

Might need to be ridden, could also be affected by Valve adjustment. If #3 is completely out of adjustment it could be holding that valve open a little & letting the "bang" out

If so it's not doing your valve seats any good... a check wouldn't hurt. Use Suzuki method not Clymer.

[Tofuball]

Allright, I'll try riding it first! Know any good ways to find out if it's the rings or the valves?

I think the leakdown test is saying that it's more likely to be the compression rings.

Also, the plug on #3 indicated a rich running condition, unlike the others.

Also, what is the "Suzuki Method" ?

[TireSmoke]

There is too big of a difference between the lowest & highest pressures. There is also quite a big increase in pressure with oil indicating rings are in order. the rich condition on #3 could just be inadequate combustion due to low pressure.

[Tofuball]

Well, I just checked and my charging system is shot too.

Also the big red wire coming out of the fuse box behind the battery gets pretty hot while running.

Seriously, with the charging system shot, the engine needs to be rebuilt, likely with a bit of head work, the carbs need to be rebiult and resynchronized, the body is trashed, turn signals don't work, etc etc . . . I'm not happy about this.

At least it has decent tires?

Honestly I'm thinking about just selling this thing

[salty_monk]

Get the valve cover off & check the clearance of the valves. If you do a search under my name you will find a post from Nessism with the Suzuki method of doing it attached. You can just print it out.

You need a set of metric feeler gauges. www.z1enterprises.com if you can't find them elsewhere.

I have a feeling that valve is out of spec & giving the low figure.

Dan

[chef1366]

The oil in the cylinder trick is raising his compression substantially which usually points to rings. I would put some PB Blaster in the cylinders and let them sit for a couple of days while adding more each day. Maybe this will break loose the troubled rings.

[Tofuball]

Good, cuz I just finished rebuilding all the carbs :P

Thanks again!!!

[Tofuball]

OK, new question. when I took the carbs off to rebuild them the "intake manifold" part came apart with them. All four of mine are broken.

What in the world am I supposed to do about that?

This bike is just more and more trouble . . .


Thanks for your help!

[Nessism]

OK, new question. when I took the carbs off to rebuild them the "intake manifold" part came apart with them. All four of mine are broken.

What in the world am I supposed to do about that?

Replace them, along with the large O-ring sealing them to the head.:shock:

[salty_monk]

The oil in the cylinder trick is raising his compression substantially which usually points to rings. I would put some PB Blaster in the cylinders and let them sit for a couple of days while adding more each day. Maybe this will break loose the troubled rings.

Looking at the figures again, I bow to your greater knowledge :-D

Checking the valves when you don't know the history of the bike is never a bad thing though.

Dan