Well, it's finally happened.

At 193500 kilometers, the old Vee has experienced a, shall we say, potentially catastrophic failure.

Arriving home in the dark after a 45-minute highway commute this evening, I pulled up to my gate and thought, "What's that smell?" Then I noticed the cloud of steam rising up around me, illuminated by the cold glow of my LED headlights.

I opened up the gate and rode it into the shop and it's leaving a trail of coolant all the way in.

I'm thinking, "I hope it's just a hose worked loose," but no such luck. It's the front cylinder where it meets the engine case. I suppose I can count myself lucky it let go just as I was arriving home.

Who out there has done this job? What kind of project am I looking at? How far into the belly of the beast do I have to go?

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Oh Rats. Looking forward to reading about this cure. Good luck-

Looks to me like a base gasket has let go...Time for a top end tear down to freshen it up...valves, maybe rings, water pump complete, gaskets, O Rings...Great Winter project !

You come on up and do it. I'll supply tools, a heated shop, and buy the beer.

Unfortunately, this is my year-round ride. I think she's down for a while, so some creative planning is in order. KTM? Honda? My next bike fantasies have just become real. Unfortunately, I just gutted the entire lower floor of my house, kitchen included. While my kitchen looks great, my bike fund is not pretty.

I think I'm driving the Taco for a good while and tearing this bike down over the next couple months. (It's future is the track anyway. Still a stout engine on this thing.)

Does anyone know if this particular job can be done without removing the engine? My initial thinking is that it can be done. I remember having the rad off when checking valve clearances and thinking there was lots of room. Time also for valve shims, maybe valves. I think the rings are still plenty good. Absolutely zero oil use. (Synthetic its entire life.)

Trying to figure out which gasket it is on the fiche: https://www.mrcycles.com/oemparts/a/...-cylinder-head

Doesn't look like it's in this schematic...

It's not part #5 which is further up the cylinder head.

Well, If you were in a 50 mile radius of Central California, I might consider it...Substitute the beer for Dr. Pepper and even more enticing...But your photo looks to me like a base gasket between the Cyl. and engine case and yes, This not an overnite repair job...

Can't tell by your photos, but did you look where the radiator hose goes into the back of the cyl. head. There is a metal fitting the hose connects to. That fitting is held in by a single bolt. There is an O-ring on that fitting to seal it. I've had 2 different 650 motor where those O-rings turned to mush and started leaking(Looking much like your photo).
I fixed mine in a day. It requires removing the injectors to access.

I would make absolutely SURE the leak isn't from above that area.

If it is the cylinder base gasket, I think it could be repaired on the bike. The front cylinder head can be removed while the engine is in the frame iirc. That will give you room to lift the cylinder and replace the base gasket. There are other things that could cause the base gasket to leak, such as loose fasteners or corrosion. You will have to watch for problems as you tear into it. But, if the engine has been doing just fine I don't see any reason this could not be made right pretty cheap. This is a labor job, not so much new parts.

You would need Part #3 in this diagram to fix the base gasket. You would also need a new head gasket and maybe some of the other rubber seals if you want to have them on hand. There are other parts you may want to replace while you are in there like hoses.

Honestly, It's a full day of work, if you have every thing you need to do the job and have the skills needed. There's some decisions once you are in there though, like checking cam chain and guides, do I put new piston rings and have the cylinder honed etc. Those things may drag the job on for much longer if you have to order more parts. Do check the valve clearance before the complete teardown, so you can replace the shims if necessary.

Thanks guys.

I'm almost positive it's the base gasket and not anything else. I had a good look (well, as good as I could in the dark with a halogen lamp).

I hope to get a closer look this weekend. My plan at the moment is to tear it down and see what parts I'll need. In particular, I'm not looking forward to removing the exhaust. I anticipate some difficulty there. (This bike has suffered a "bit" of corrosion over the last 12 salty winters. I'm hoping that is not contributing to the leak.)

I'll document the process for posterity.