diagnosing aging motor?

[jwm]

I've got a 1996 XR440 that has seen moderate use and has been reasonably cared for.
The low-end was rebuilt when 3rd gear went away and had to be replaced,
but the valve train wasn't done then.


It has started burning oil, and I want to make an assessment of the "health"
of the motor before I tear into it.
I adjusted the valves not long ago; the exhaust valves were a little loose.


In the past when at this point, I've taken bikes to mechanics I trust, and I may
well end up doing that again. But I want to dive deeper myself this time.
Ideally, I'd like to learn something about basic 4-stroke engine diagnostics.
If I have to, I'm not against spending $ on tools to help.


I've seen the 4-stroke leak-down tester that Motion Pro sells
(Motion Pro)
but I'm not sure if it would help me figure this out.


I've seen excellent tutorials on suspension settings, carb theory and jetting.
Does anyone know of a good tutorial on assessing valve train health?


-- jeff

 

[crkid]

Check Eric Gorr's site, he's got some books that I've heard are very good. If you don't see anything there, ask Eric he knows what he's talking about.

 

[jmics19067]

you will never go wrong talking to Eric . A cheap way of getting around a leak down tester< but not as accurate> is to have a compression tester. Take out the spark plug and screw thw compresion tester in and kick the bike over. I believe this woudl be true on the xr's but only give half kicks because he top part of the kick starter acts as an automatic compression release. read the gauge as you are kicking. Take out the compression tester squirt some cleanoil in the spark plug hole and reinstall tester and kick thru again. If the gauge jumps up to a higher pressure quicker and/ or you have a final higher pressure it is probaly the piston /rings.

Does your bike smoke? if it smokes when you first start it it is probably valve seals, if when you ride at a good pace and then let off the throttle and letthe engine slow you down and smokes worse it is probably piston/ rings. that is if it is blue smoke fromoil burning.