Hi. Just got an XS500....

[SOHC4]

Well, there doesnt seem to be any forums for the XS500 so mabey someone here knows of one? Mabey this site is the best Ill get since they arent an overly popular bike like the 1100. Im not new to bikes, I have a couple CB550's, one that I restored/modified, a Tiger 750, and now I just got an XS500, in great shape, for FREE!! Black with gold pinstriping, everything original exept for the rediculous 50 pound faring someone decided to strap on the poor thing. So first off, Im looking for a complete headlight. Ebay had none for the 500, but plenty for other models. Id like to get an original, but if other model headlights will work and are close to being the same, please let me know.

It didnt take me long to figure out why my co worker gave me this bike for free....no compression...at all. Which I find strange since only a year ago he fired it up for me and it ran great. I can tun it over with minimal force with my hand and you can push the bike around pretty easily with it in gear. I went ahead and hooked a battery up to test electrical then went ahead and hit the starter a couple times. Turned over very fast, as expected, and oil instantly started pooring out where the oil filter meets the crankcase. Heres my guess since I havnt seen the guy in a week to ask him what the hell he(or his crotchrocket wrecking son) did to this poor bike: He changed the oil and filter, put the new filter on, either put the wrong size on, or didnt get it on tight, fired it up, ran the oil out of it without realizing it, and killed the rings. Is this viable? Would the motor have just locked up or is it possible that the high heat caused the rings to warp/loose compression and the motor remained free? Ive never done anything that stupid to a motor, so I dont know the results for such a mistake. If this is the case, would I be ok with stock rings and running a hone through the cylinders, or would it need to be overbored with oversized pistons fitted? Sorry for the long post and thanks if you read it all.

[wingnut]

Get the bore gages out

About all you can do is take it down and look it over. Measure the cylinders and look at the pistons. Rings can fail from over heat but piston damage could have happened at the same time. If it was run without oil the bottom end may be toast also A hone job and new rings could be all it needs but the only way to tell is to measure things and see how much damage has been done.

[prometheus578]

Open up the top and check the valve timing. I'm not familiar with this model, so I can't go into detail. the cam gear, if seperate from the cam, could have come loose. the cam chain could have broken, these things you could see once you've taken it down a little.
The cam chain could have slipped, gone out of time, and you're looking at bent valves. This stuff would be the first thing to check for on your way to removing the head and checking the cylinder and rings.

[TopCatGr58]

A little down memory lane!

Hey there SOHC4,

If you go to the links section, you'll find one to the Official Yamaha Online Parts Fiche site. There you can view exploded views of almost every component of your machine.

The DOHC 4 valve per cylinder, twin 4 stroker, with counter balance shaft, was first used in 1973 with the TX500A, and continued till 1978 with the XS500E.

The cam uses direct rocker arm styles with lash adjusting screw/nuts. The heads were known to crack in between the valves under heat stress, and dropping valve seats.

I had a 74 TX500A, fairly strong machine for it's size!

What Prom and the others have said, many ways to loose compression, burned holes in pistons, bent valves from jumping teeth on excessive rpms, etc.! Good Luck!
T.C.

[SOHC4]

Hey, thanks for the responses gentlemen. Ill be looking into these things as I tear it down and I'll of course be picking up a shop manual before doing so. The exploded diagrams will help alot until then. Thanks!

[e.z.nightrider]

Check out XJBIKES.COM it's a forum like this one for the XJ Maxum and XJ Seca Yamaha bikes.

Ed Z