Think I need new rings

The bike - a 1987 XJ900 with 110,000 kms
The bike runs well and starts first hit. She uses practically no oil. However after recently buying a compression gauge I've discovered 135 psi on one and under 50 on the other three. The low ones all improve to 100 when a teaspoon of oil is added. This suggests to me I've got some rings issues. I'm thinking of tackling it myself so is there a how to on the site?

I think I will need the fol:
Rings, Head gasket,base gasket, tappet cover gasket, replacement o rings. Do I need any sealants? Does Len sell any of the above? I also want to source some ring compressors can anybody direct me to a source? Stateside ok! (I'm not interested in making my own with hose clips etc) Any help would be greatly appreciated! Oh, One last thing, how do I deal with the cam chain? Timing etc....

 

Have you checked the valve clearances yet?

 

No, my understanding is that if the compression improves after adding oil its rings

 

go to oldbikebarn.com and u can buy a complete engine gasket kit for like 160 bucks, cheapest ive found, and bike bandit wasnt to bad for rings, like 62 bucks a piston for a 650 anyway

 

well CHECKING the valves is free. (maybe you gotta buy feelers) The valve cover gasket oughta be reusable if not in horrible condition. You'd notice leaking oil if it were.

besides, conservation of effort. you have to dig through the valves on your way to the rings.

 

Check those valve clearences before you condem the rings. While you are correct that addding oil will help seal the rings for compression testing. If the valves are out of spec and tight it will case low compression readings. Another sympton of worn rings is oil burning, you did say that is doesn't use much oil. Does the bike smoke any?
Check the valves and re-do the compression test.

 

Starts first hit - - with 50 pounds on 3 out of 4 ??
That's unheard of. It shouldn't even idle. 8O

+1 on checking clearances and double-check compression (throttle open, battery up, all 4 plugs out)

 

I agree. Something's wrong with the test, the bike won't run on 3 50psi cylinders.

Get your valves in spec and borrow a different compression gauge.

 

The gauge is brand new and of fair quality. Furthermore, I can hold my thumb over 3 of the bad cylinders and easily hold their compression in. I'd like to blame valve clearances and will buy that theory if somebody can explain how adding oil can suddenly fix the valve clearances!

 

oil is thicker than air.

same deal as for rings.

 

I agree, the test numbers are crazy, under 90 psi or so and it just won't fire at idle.

Not sure what type of gauge you are using, but ... there are basically two types and they require a different technique for each.

The cheap ones have no valve or relief valve, and they don't hold the reading. With these the needle goes up and down with each stroke and you just look where it gets to each time to see what the maximum is.

The more expensive, and generally much better gauge, has a valve that looks like a tyre valve in the adaptor that screws into the plug hole. The valve holds the pressure in the gauge and hose and the needle bumps up a little higher each time. With this sort of tester you let it pump up about 5 to 10 strokes and then check the maximum reading before letting the pressure out for the next test.

If you are using the second type and are getting weird numbers like this you might have a bit of carbon stuck in the valve, it's a common problem with this sort of gauge. If you got one high reading followed by three very low ones I'd take the valve out and check it is sealing correctly.

 

The combustion chamber is 23 CC's, you added 11 CC's of oil so, the same amount of leakage records twice the pressure.

Let's hope it's valve clearances and not the big job of rings.

 

mmmm I see....after searching Google on this topic on every site I visited it indicated that if the pressure increased after adding oil then its a rings issue. I'm puzzled as to why I've had no support for this theory from the XJ folk? Cue Rick CoMatic!

Contary to the above posts the bike starts and runs fine even though compression is very low on 3 cylinders....as I said earlier I can EASILY hold my thumb over the plug holes but not on the good one....

 

I know what you what you mean Adrian1 I swear every site I have been to and every book I have read states without exception that Adrian1s have to buy Waldos beers until such time he (Waldo) burps the alphabet.

 

i love the humor here...it's better than comedy central