Poor Compression - Warped - Damaged???

[fishermanpenner]

ok, to start off this is my first xs650. I bought it completely rebuilt and I believe a made a big mistake and am paying for it now.

My bike only has 2500miles on the new engine, I took it to Sturgis this yr and ran it pretty hard on the highways out there. I was starting to hear a rattling noise when at highway speeds, but wasnt able to find anyone that wanted to work on a Yamaha in Harley Country!!. I got the bike home, and now when I kick start it it almost feels like the cylinder heads are warped????? feels tight going up, and then loosens going down. (that make sense???) Checked compression on both cylinders, had 115 on both. I have the big bore kit from Mikes XS - not sure if that makes a difference. (most parts are from there) The bike got pretty hot, running at 70mph, then sitting in traffic for 30mins.

I for the lack of knowledge, got the bike and rode it, didnt do any adjustments on anything motor wise. The bike only had 300 miles on it when I got it, Im thinking after doing my research that I should have been doing some regular maintaince adjustments etc.... When I changed the oil before my trip, I did notice some very fine metal filings on the oil plug, I assumed this was just from break in.

I just ordered an engine stand since I assume i'll be pulling the engine out, any ideas as to what I may have done to it?

 

[xjwmx]

Hard to say what the rattle is without hearing it. Might be just a loose cam chain. Can even be something like a loose head pipe. The kicker shouldn't go down easier than it comes up - it should come up by itself under spring power and go down with a fair amount of resistance. When you checked the compression was the engine warm and especially did you hold the throttle all the way open? Both will give a higher reading. And did you keep cranking until it peaked? 115 is low for a 650 and I think the 750 kits give higher than the 650. A little bit of metal on the drain plug isn't necessarily the kiss of death it would be with a car. Hopefully the engine stand was premature. You might need to take the right cover off with the engine in the bike to see what's up with the kicker. I don't think your heads are warped if you don't have prolific oil leakage.

I rode my xs to Sturgis too, but purposely a couple weeks after the big event. I camped on some lake not too far from town and had it all to myself. Don't remember its name but I remember a big entertainment complex all by itself opposite the road you turn off on.

 

[5twins]

Have you re-torqued the head at all since you got it? That's a pretty important "must do" after a rebuild, in fact several times in the first about 1000 miles. If you haven't, maybe the head bolts have come loose, the head gasket is consequently leaking, and you're losing compression.

 

[fishermanpenner]

No, when I tested the compression the engine was cold, and no I didn't hold the throttle open. I'm going to try that ASAP. For the 2nd post, no I didn't re-torque the head bolts either, again I'm going or look at that ASAP. For the kicker, it's more the feeling of the cylinders or what ever that I can feel the difference in resistance that I'm referring too, the kicker is fine itself.

Hopefully your right about the engine stand! I'm all new to this, and I immediate fear the worst. Thanks.

 

[xjwmx]

For the kicker, it's more the feeling of the cylinders or what ever that I can feel the difference in resistance that I'm referring too, the kicker is fine itself.

The kicker resistance is different depending on where the engine is in its rotation. It'll give the most resistance when one cylinder is near the top of its compression stroke. At other points it'll turn almost freely. So overall it will feel sort of "lumpy". If that's what you're feeling it's a good sign - it means you have some compression

 

[peanut]

I suspect that the rubbing , rattling noise is unlikely to be the cam chain rubbing on the cam chain guide as it should have been replaced on a rebuilt engine.

One other distinct possibility is that the builder left out one of the clutch spacing washers or got them in the wrong order. Its a very common problem.

There should be 2x spacing washers behind the clutch basket and they need to be in the correct order. The gap between the rear of the clutch basket and the crankcase is just a few mm .

If one of the washers are left out the clutch basket grinds on the crankcase gouging a deep groouve and producing a lot of aluminium dust. It will also make a rubbing noise and produce a lot of friction and heat and you would feel the rubbing effect when kicking the engine over as the clutch basket grinds on the crankcase.



Remove the cover and measure the gap behind the clutch basket with a feeler guage. It should be at least 2-3 mm.

see this thread and image
http://www.xs650.com/forum/showthread.php?t=29337&highlight=clutch+washer

 

[XSLeo]

On my 75 with the 750 kit, on the engine stand, after the rebuild, no carbs, full of assembly grease, cranking with the starter it got 195 psi compression. I haven't checked it since. I think it may be a bit lower now the assembly lube has flushed out. I have a few thousand miles on it now.
The noise you hear may be the cam chain, they get noisy when not adjusted right. I would start with a can chain adjustment, then a valve adjustment. This may quiet your noise.
Leo

 

[fishermanpenner]

Thanks, yah I'm going to start with the easiest things first, cam chain and then Move forward. Hopefully I just checked my compression wrong, I'll try again soon. Thnanks everyone for the tips! I'm a serious newbie, so it all helps.