CR 85 Radiator question

[Wolf]

Quick question:
When we start up our CR 85, coolant instantly gets pushed through the radiator over flow tube. Rev it up, more comes out. We ended up cooking the 85 that way. Could this just be a faulty radiator cap? The spring on it seems not very "springy" meaning you can't really compress it much. the spare one I have laying arounds is slightly different, as the spring seems to be taller and the seal a little smaller....(came off a busted CR 85 radiator, probably a different year though - ours is a 06.

 

[ellandoh]

i can run my bike with the cap off and it wont overflow until the liquid heats up and expands. seems as though you are pushing more liquid than youre pulling, i would think about some type of restriction...........but thats just a guess. does the cap feel "normal" when you twist it on? did you try the extra cap? do you still have the busted rad to compare the necks.

just .02$

 

[Wolf]

Hmm...didn't think about restriction. How do I find out? I guess I candump in at the top and drain at the bottom drain screw?
When I pop the cap off (when hot), it doesn't seem to be under pressure. The cap doesn't feel like it is under much tension at all when you pop it on or off at all.
I don't have the old Rad, but the caps seem to match up. I haven't tried it yet, as I didn't find it until late last night. Will mess with it some more tonight.

Update: Spoke with EG...he says it's likely a blown head gasket.

 

[longtime coming]

Yes, that is a blown head gasket.

 

[Patman]

Wolf the CR85 is a pretty notorious little head gasket leaker. You should check to make sure the base of the head and the top of the cylinder are perfectly dead true. Eirc told me to unbolt it at the base when changine rings / pistons after he built our super mini engine. I may have a spare brand new CR85 radiator and cap in the trailer...

 

[Wolf]

Patman,
I'm going up to Erics shop on Saturday, we'll fix it there. that way he can mill if necessary. I'm guessing we roached the top end anyway, by riding it and not realising what was going on. Probably scored it pretty good.
I could use a spare, if you have it I'll take it...lemme know.

 

[kx2502009]

head gasket bro fix it before she blows

 

[Patman]

OK Wolf I got hands on the OEM radiator and cap. It's new as in came off a bike with maybe 5 hours and not crashed and has the factory 1.1 cap. Talk with EG and then decide if you want it or a Fluidyne. I'll hold it until I hear from ya. either way.

 

[Wolf]

Pat, went with a Fluidyne. Thanks for the offer!!!

 

[Patman]

Good choice! We ran one too and had this one as a just in case something bad happens we don't lose the ride spare.