OHH SH*T!!!!!!!!!!

Last night was not good. Rode trails for 10 minutes then rode to the gas station to top off the tank. Rode back into the woods, started up the mountain the bike stalls. I'm thinking I must have kicked it up a gear or two by mistake in the corner. Bike starts right up. Give it a little hell up the small hill climb, get to the top, it dies. I look down and theres oil, EVERYWHERE! I'm thinking **** , I must have cross threaded the drain bolt, oil heated and now it's everywhere. I get it home, upon further inspection the stinking oil reservoir plug came out!!! How that thing loosened up I'll never know. I am pretty anal(like we all aren't)about tightening and maintenance in general. So anyhow I immediately drained the small amount of oil left in the case and checked the filter. No excess metal in the filter. I put more oil in and it started right up, no loss of compression etc. What happened when it stalled? Did it overheat and sieze momentarily? What am I looking at here guys?

My bike seized several times 2 years ago. I traced it to starting it in deep water with the water level over that stupid head vent that runs along the main frame's downtube. When kicking it over (in the water after stalling out), it sucks all that yummy, delicious, clean (with the exception of all the dirt) water up into the head. I have a reasonable amount of scoring in the cylinder now.

You can always tear it down to check main bearing play and cylinder/piston wear. If left unchecked, you will always wonder what the damage really is, and if you will be stranded in the middle of nowhere due to main bearing seizure. Grim, but true.


'99 WZ with ALL YZ mods, de-octopused, DSP Doug Henry airbox w/ velocity stack, FMF PowerBomb header, Stroker SX-1 silencer, SS front brake line, forked over by Pro-Action (and then fixed by me), OEM YZ tank, IMS YZ seat, carb mods by Jim Dean, Andy in OZ, & Sir "Taffy" from Jolly Old England, AMA, NESC.

I re routed my oil vent tube so it drips on my chain. It makes a mess but keeps a slight oil film on my chain. it's messy, but I don't give a crap about the appearence of my bike. I concentrate on the important things like all moving parts, motor and beer.

Appearence wise my 01 426 looks like crap, but mechanically it's a.o.k.

C2: Hmmmm....this is a difficult one. It's difficult to predict....or ascertain any damage that may or may not have been done. From your description, there are some positive signs. Compression is still good...you still had oil in the crankcase. As far as the relationship between stalling and loss of oil...I don't know. Like you, I would be concerned about excess heat caused by lubrication loss. If it were me...and from what you have described....I suppose I would start from scratch and put oil back in and pretend like the bike was brand new....paying particular attention to exhaust smoke when it's first started...and any unusual mechanical noise. If you are like me, every time I change my oil and start the engine, I put my ear a few inches from the cases on each side and just listen(ear plugs help with this since the plugs filter out superfluous and extraneous noises)...and put my hand on the cases and FEEL. By doing this, I have gotten to know what sounds and feels normal..and what doesn't. Anyway, take it easy for a while and see it the engine stalls again without reason....watch the exhaust for smoking...etc. The way I see it, if the engine has been damaged, it will show up pretty quickly, if not, you haven't spent money needlessly. It seems to be the opinion of many that the YZ engine design lends itself well to momentary oiling losses and will survive with no appreciable damage. I dunno.

Something just occurred to me. The 1700cc oil capacity of these machines helps to remove internal heat. The frame tank reservoir capacity helps to dissipate heat as the oil circulates. Possibly, as you lost oil, the heat increased quickly and the tolerances may have increased to the point that things got tight. If that happened, then friction and wear comes into the equation. I can certainly understand your concern. Good luck.

[This message has been edited by Boit (edited 05-16-2001).]

The pump would have quit delivering oil to your motor more or less as soon as all the oil ran out of the reservoir (thank you Capt. Obvious). If oil ran out the lower oil filter cover bolt hole (the allen head one) like normal when you removed it then the pump was probably still pumping something.

The rod bearing and then the cams probably take oil starvation the hardest judging by the way they are oiled, the other bearings in the motor aren’t really pressure oiled, and you had at least some oil in your cases.

I doubt you’d be finding debris in your filter regardless, if the pump(s) could deliver it there then you are obviously circulating oil, so whatever evidence of engine damage that exists is either in your cases and remaining oil, or out there in the woods. You may consider flushing the cases via the drain plug into a drain pan; just remove your right cover and lay the bike on that side and see if anything scary comes out. If you still have the remaining oil run a magnet through it, and check your rotor, metal will stick to the magnetized inside portion.

If the motor gets hot enough it can stall due to the extra friction, I’ve done this to my YZ before when I lost all my coolant and long term consequences were nil. I’m lazy and reckless so I didn’t pull anything apart until much later to re-ring it and everything looked fine. But losing oil pressure would make me a bit more nervous. FYI you can check the rod bearing and valve train without splitting the cases or yanking the motor.

Hope this helps.

[This message has been edited by Hick (edited 05-16-2001).]

Thanks for the info. guys. I was messing with it last night and there was nothing out of the ordinary re: sound, smoke, power etc. It was really strange when it stalled. There was nothing violent or sudden when it happened. Kind of like I ran out of gas all of the sudden. Then it kicked right over. Going on a real ride tonight, guess we'll see what happens.

Maby someone from above stalled your bike so you would see the oil ? There realy is a motercycle God Amen :)


your achilles heel is your BIG END. THAT'S THE FIRST THING TO GO.

i think you've either damaged this or you've became a bit nervy when riding it & you aren't giving it enough revs.

i think you're going to gain in confidence & it'll all be OK.


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