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Discussion Starter #1
I'm about at my wits end here.

So a few weeks ago when I finally got my 'fighter registered and all that good stuff... I finally ventured out into the big wilderness of the bay area freeway system... and promptly sprung a coolant leak as soon as I wound the bike out to redline.

It wasn't critical; I still had plenty of water in the system by the time I got home, but still annoying as hell. I eventually tracked it down to the O-ring that seals the coupling to the thermostat housing from the front cylinder head.

I pulled the throttle bodies and the other under-tank guts, pulled out the coupling... and found the o-ring pretty much destroyed. Must have pinched it on install. I pulled the rear one just to be safe, it was also kind of damaged.

Went down to the shop and picked up some replacement O-rings.

Installed them... filled with coolant. Drip drip. Took it apart again, realized that I hadn't tightened the bolts down enough (I was being super cautious in an effort to avoid crushing the O rings again), inspected the O-rings one last time (no damage). Patched it up, refilled the coolant, everything looked cozy. Rode to work, etc, etc, etc. No leaks. Rode to school. No leaks. Went by the bike shop where I do all my business to show the finished project off, guys wanted to hear what she sounded like WFO... so I indulged.

Drip drip drip drip drip.... coolant leak from the rear cylinder's thermostat coupling O ring. >_<

Ride home... (it was a slow leak, I lost ~4 ounces of water in the 15 miles it took to get home), check the connection before committing to pulling the bike apart again. Oh! The bolt for the rear coupler is kinda loose. Twist twist twist. Leak stops! This was on friday.

Fast forward to yesterday. Ride the bike to work. Its great; I'm getting used to the bike's responses, able to really start being aggressive with it. No coolant leaks. Ride to school from work. No coolant leaks. Wind it out right before getting off the freeway coming home. COOLANT LEAK!

Rear cylinder, still.

Bottom line; every time I take the bike above 10k RPM, one of those bloody O rings starts leaking under the increased water pressure.

WTF do I need to do to get these things to seal properly? Do I need to completely disassemble the coupling unit? I've been installing the thermostat with both hoses and couplings as one unit (which is how I believe the manual says to do it). Plug in both couplings and install the bolts, tighten them down. Do I need to take the couplings off their hoses, install them, then install the hoses and thermostat?

Can I just seal the buggers off by coating the O ring in some nice high temp liquid gasket? The leak is tiny.... just a little trickle of low pressure water.

It's driving me nuts. Everything else on the bike is working fine. I really want to be able to ride this thing with no worries... but as long as she's dripping like an incontinent geriatric, I can't!
 

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1) Are you sure they are the right size, both circumference and diameter (thickness)?
2) Are you using a torque wrench on the fasteners?
3) Yes, you can try sealing with high temp silicon engine assembly "instant gasket".

I'd verify the first two things. Consider using some O-ring grease if you decide not to try the silicon (Dow-Corning 111 or equivalent silicon grease).
 

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Discussion Starter #3 (Edited)
Yes, the O rings are the right size.

No torque wrench on the fasteners, given that I can't find a recommended torque anywhere in the service manual. I'm tightening them until the stop tab on the coupler snugs up, then giving them a half turn or so.

I'll try some more grease; the rings came prelubed, but maybe it isnt enough.

I'm more inclined to try a nice bead of gasket maker though.. i'm reasonably sure that will work.
 
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