Coolant in crankcase after rebuild

[Jacob 'Berg]

After my bottom end rebuild and replacing the top end I could not get the bike to fire. Pulled the crankcase drain and about 3-4 oz of coolant spilled out. Any ideas on where this may have come from? Bike ran maybe 10 seconds before dying, but I kicked the living day lights out of it trying to get it to fire afterwards. Head O-rings, base gasket, center gasket? Any other possible areas where the coolant could get into the crank case?

[Jacob 'Berg]

I pulled the head off and the O-rings are seated correctly. I will pull the jug next and look at the base gasket and the mating surfaces on the cylinder and case halves. If I have to split the cases again, where should I look?

[gasgasman]

The only place that coolant can get into the crankcase is at the coolant passage that crosses through the case halves at the front.

[Jacob 'Berg]

Originally Posted by gasgasman

The only place that coolant can get into the crankcase is at the coolant passage that crosses through the case halves at the front.

Thanks Girard. I guess the cases are coming apart again, unless it is the base gasket I thought the mating surfaces were clean before putting the halves back together. Should I use any RTV or sealant in this area to ensure I do not have another issue?

[(F5)]

ERM. . . the waterpump.

[Jakobi]

Was the coolant in the crank case or the transmission?

What made you drop the crank case? noticeable loss of coolant with no external visible signs?

You'd be quite unfortunate to damage a gasket in the area where the coolant runs across the front of the engine. Very unfortunate. Not impossible though.

How do you know the head o-ring or base gasket didn't leak? Kids been playing in the shed?

[Jacob 'Berg]

Originally Posted by (F5)

ERM. . . the waterpump.

Unlikely, as there is no coolant in the transmission oil, just in the crank case and cylinder.

[gasgasman]

Originally Posted by Jacob 'Berg

Should I use any RTV or sealant in this area to ensure I do not have another issue?

Absolutely no RTV. The fuel will dissolve the silicone.
If you do wish to use some sealant, use Yamabond.

If you use the wrong bolts on the case halves, that can cause a coolant leak. Too long of a bolt will bottom out before it tightens.

[barossi73]

If its coolant in cylinder its most likely orings.id bet 1 has jumped out slightly when head has seated.took me a couple attempts and some careful stretching to get mine to sit still long enough to clamp down.check the oring grooves carefully for any grit.if you do take cylinder back off for base gasket, check the studs are tight before reassemble.did you torque correctly the head nuts or go by 'feel'?

[Jacob 'Berg]

Originally Posted by gasgasman

Absolutely no RTV. The fuel will dissolve the silicone.
If you do wish to use some sealant, use Yamabond.

If you use the wrong bolts on the case halves, that can cause a coolant leak. Too long of a bolt will bottom out before it tightens.

I had the bolts stuck through a sheet of cardboard so that it matched the profile of the bolt pattern in the cases.