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.

[Jacob 'Berg]

Originally Posted by 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?

Coolant in the crankcase and cylinder. Not in the transmission.

I dropped the drain bolt because I could not get the bike to fire after my rebuild. This was part of my least invasive troubleshooting process.

New O-rings were seated properly. It could be the base gasket, I will pull the jug next.

If it is not the base gasket it appears the leak will be between the case halves.

[GGRider01]

I'm mostly curious where the crankcase drain plug is located on these engines.

[Jacob 'Berg]

Originally Posted by GGRider01

I'm mostly curious where the crankcase drain plug is located on these engines.

The drain plug looks similar to the transmission drain plug. It is located underneath the cases, towards the left (pilot's left), under the crank (closer to the front of the cases).