am i retarded or does this have one valve seal

so my xr100 burns more oil than an oldchool oil lamp so i pulled it apart and its in pretty bad shape. guess the previous owners neglected the crap out of it. cylinder is pretty chewed up, piston rings leak, valve seals leak, cam journal is chewed to shit. anyways when i got to the head to take the 2 valve seals out, i became dumbfounded when i found only one seal. after i inspected to see if one of the seals just dissapeared and got eaten by the cam sprocket or lifters, i noticed the valve guides are totally different. i have no clue how one seal for 2 valves works. so does the bike really only have one valve seal?


Congratulations, you're not retarded. The intake side is a guide only, yes different than exhaust.

Have a look at your oil slinger/filter, most likely packed with crud / clutch media.

so no matter what, it will always leak some on the intake guide? and also i was tightening the spokes today and i looked for the oil filter area but it looks like im gonna have to pull the whole right side cover off?

shouldn't leak very much and ya i think your gonna have to take the right side cover off its no big deal, i think it will come straight off if ya take the kicker off

yeah ill go pick up an oil filter and then inspect the area. i bought a gasket kit so i can just replace that gasket cause i bet its gonna fall apart since its like 14 years old. the seal and rings are the only 2 ways it can burn oil right? so even if the filter or slinger is clogged up then it wont make much of a difference? just make the oil flow better

yeah ive spent a lot of time looking at parts diagrams in my day. i didnt look too much on the xr yet. anyways its a 1996

another quick question, i bought some piston rings that are .25 over. am i gonna have to hone to get those to fit? or do you think they will pop right in?

Is your piston/bore .25 over and still good?

the piston is stock. not .25 over and the bore is also stock

You need a .25 over piston and bore it to match the piston. You actually have to give the machine shop the piston, because pistons can vary. 2001 - present heads have two valve seals. That journal look pretty hammered.

Oversize rings need an oversize bore and piston. You may as well overhaul the top end; bore the cylinder and replace the piston with a .25 oversize. Replace both valve guides and call it done. As a second option, has there new and improved big bore kit coming available shortly, probably 250 to $300. As socalxr stated, your cam journal is in rough shape. You may want to reconsider this engine.

There is no oil filter per se; it is a slinger that catches the debris from the clutch etc. After pulling the engine cover, look for a funnel shaped piece just in front of the clutch ass'y, on top of the primary drive gear. Pull the cover off (three bolts) and clean the area behind. There is a gasket on the cover which you will need to replace.

There is a oil strainer at the base of the engine, directly below the pump which could be cleaned as well.

XR/CRF100's don't have slingers.. Early 75's, 200's, and a bunch of other motors do, but not the XR80/100.

yeah thats true. maybe ill just refund all the parts i bought for it

well what would it even cost for a machine shop to do the .25 bore?

also what if i just got some head on ebay that seems to be in good shape? its not important for the bike to be finished very soon so its okay if i keep an eye out and find one in a couple months. i couldnt find any for an xr100 that i was willing to buy but i found there 2 for an xr80. would they fit my 96?

Edited by aids

i may have found another reason it burned so much oil. the cylinder has some pretty bad pitting and scratches on the cylinder walls

heres the one that came out of it


and heres the new one


The piston rings are probably worn out. Take the rings off the piston and measure the ring gap when they are inserted at several locations within the cylinder bore. You can measure the gap with a feeler gauge.

I have my son's 2000 XR100 engine apart now because it was smoking more than our KX100. The ring gap is supposed go be between 0.010" and 0.020". My son's was 0.038".

Your cam journel looks "unhappy" you can use plastigauge to check the oil clearance. The limit is 0.008".

FYI - I found the BBR 120 kit on Ebay for $259 shipped, but if your head is shot too you may want to consider another used engine and sell your old one for parts.

maybe you want to sell me your cylinder? the old one

I will send you some photos in 10 min.

Send me your email address via PM and I will send the photos.

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