Compression on XR100?

[veloc1ty]

What is the compression supposed to be on a XR100? I got 140 psi on my 99' XR100, but it feels like it may be losing compression. Is it time for new rings?

[fivepointnine]

140psi actually kinda sounds high.

[4 STROKER]

A good stock one puts out 160psi.. Throttle wide open:thumbsup:

[socalxr]

Yep, the manual says 164.

[veloc1ty]

Is it time for a new piston and rings? Will I have to mess with the valves any?

[socalxr]

You should have your repairman take a good look at it.

Repairmen are for lonely house wives.

I would go one over on the bore and check the valves using wd40 to see if they are leaking. You could also get a trail bikes 115kit for about $200, which is just a little more than a piston kit. But if you plan on getting a BBR kit or something later on, then just spend as little as possible for now.

[veloc1ty]

Thanks for the responses. I didn't really plan to put a big bore in it since my sister is moving from a xr70 to the xr100. Could you explain checking the valves with wd40? Thanks

[socalxr]

Just spray wd40 into the intake and exhaust ports, then if any seaps into the other side (combustion chamber) the valve is bent (90% of the time) or worn seats or something.

[kc_450_X]

Just spray wd40 into the intake and exhaust ports, then if any seaps into the other side (combustion chamber) the valve is bent (90% of the time) or worn seats or something.

Wouldn't you need to time the engine so both valves are closed? If one or both valves were open a little you will get wd40 in the cumbustion chamber.

[socalxr]

Wouldn't you need to time the engine so both valves are closed? If one or both valves were open a little you will get wd40 in the cumbustion chamber.

You do this with the head would be off, while you're doing the piston and rings. Otherwise, you can put it back together and still have the same problem. It's pretty much should be part of your routine mainatnce when you have the motor apart.

[kc_450_X]

Ahhhhhhhhhh, I get it now.

[ssarley]

xr80 point settings??

rockerarm to valve clearance?