Coolant in crankcase = no fun

[stainlesscycle]

[stainlesscycle]

so it looks to me like inner o-ring failed massively.. and i would assume the big end pin is just as nasty as the piston pin.

[GMP]

Was that oring broken? The key word may be "massively". Usually, if the oring fails (looses tension from heat) the compression pressurizes the cooling system, blowing out coolant immediately. This happened to our 125 GG but no coolant entered the lower end and only a few drops up top, I'm sure after it cooled down. Compression pressure is a lot more than cooling system pressure. Still, I'd go over every gasket surface.

Now the question is if it overheated and melted the inner oring, why?

[HuskyDude]

I was wondering if things got too hot before the O ring gave up also.
Hey Stainless your plug (which I assume you check a lot) was OK? Like not on the lighter side of tan or white.
Any chance you mixed up fuel jugs and ran non premix??? Don't ask why I'm asking that....lets just say I don't have two identical fuel jugs any more.

[GMP]

Plenty of oil in there judging by the emulsified mess.

[stainlesscycle]

Originally Posted by HuskyDude

Hey Stainless your plug (which I assume you check a lot) was OK? Like not on the lighter side of tan or white.

that's not the plug that was in there when it stopped. i pulled the original plug out and promptly lost it on the trail. i swapped another used plug in hoping in vain that it would fire.

[stainlesscycle]

when i first overheated, there was no/very little fluid in the system. i dumped water in from my camel back. so the fluid you are seeing is from after it stopped/i refilled.


when i pulled the head the o-ring was cracked and broken/brittle. which probably happened from heat.

the centercase gasket was fine, and the base gasket was fine.


here's all i know. bike was running good, i warmed it up before the race. when i got to the first section, about 1/2 mile in, it was fine. i went a few hundred yards at wot, and my throttle cable stuck (or at least it felt like it was.) i reached down and quickly yanked on my throttle cable and it freed up. from that point on it started getting wonky. i went a few miles until it started wanting to stall out. had to fight it to keep it running.


after i refilled it on the side fo the trail, i did not run the bike. i did kick it over a few times though. hoping that magically a plug change would fix the problem and i could finish the section. so the fluid is all residual unheated coolant/water mix.

here's what i've been running through my head.

MAYBE i'm a dumbass and had an empty cooling system to begin with. MAYBE i FORGOT to refill it after i serviced it sometime in the last 2 months (bike sat idle for 2 months). i can't be sure but it's possible operator error is the problem. i'd LIKE to think it wasn't me, and i did fill the coolant (if i drain a system, i always leave the cap off...so this doesn't happen) but it is possible... it's the only logical explanation i have. because if the o-ring did fail when i was riding, it wouldn't have run well enough with a goofy mix of coolant/fuel. the outside of the cylinder is very bronze in color, which seems to me to be possibly baked on coolant/or overheat coloration. bike doesn't smell like cooked coolant. it wasn't puffing white smoke all over the place. so maybe it was me. i'd like to think it wasn't, but there's that thing in the back of my head saying, there was no coolant in there.


if it was pumping coolant into the combustion chamber, there's no way it would run for even a mile - that's a LOT of fluid to lose in a short time, that would all have to go through the crankcase/combustion chamber.. had to be my error. i have no other explanation. that would explain why the bike ran hot, why the inner oring is cracked/brittle. it would explain everything

99% of the time i do a pre-race look at the fluids etc. i did not this time - i had a nasty flu the day before, i didn't even think i would be able to race, i felt good enough that morning to race, but was still worried if i was too weak from the sick to even ride (i was so sick the night before that i slept 15 hours, and didn't eat anything after 2pm the day before...) - so my mind was elsewhere....i was still feeling woozy when i started the race.. i was afraid i'd be too weak to even kick the bike over. it was nasty.

[GMP]

Wow, I guess that could explain it. Do you run green colored coolant like Prestone, or would that be green Gatorade from your Camelback in the system? Think what you drained out equaled what you put in on the trail? Whats surprising is it didn't just seize the top end, are there score marks?

Like you I consider myself pretty organized, but I still don't trust myself. With two kids and a busy life, I cannot always finish a job when I would like to. If I have to leave the bike without oil, coolant, or a key part that is not obvious, I will put a put a wide piece of making tape on the tank with a note saying so.

Rode the Sandy Lane Enduro once with a bad cold, 40 deg and raining. Turned into pneumonia that really kicked my ass. Not worth it anymore.

[lankydoug]

When I first bought my 200 it would circulate tiny bubbles in the cooling system until warm and since I had no history on the bike except it mostly sat and didn't get ridden. I pulled the head off to have a look and the head "O" rings were flat and not very flexible. I believe it could have gradually lost coolant until low enough to have a catastrophic overheat if I had left it as is. Yours could have been in the same situation. Once they get to the tipping point it all happens fast. I wouldn't blame yourself, if you ride them they will break and if you don't they will rot. It's way more fun breaking them.

[stainlesscycle]

coolant was green colored. water only in camelback. i thought it was still green from whatever was left in there - i dunno. still unsure as to what happened. it's a moot point now, it's going back together with all new, and a different head/piston/cylinder, so if warped head was an issue it won't be this time.... have to check the failed head for warpage at some other time. probably just gonna pop it on the lathe and check runout and maybe skim it...