overheating 85 500xc

I have been experiencing some boil over with in minutes of having the bike running. I know that when at a standstill ther is no air moving through the radiators, but should it overheat that quickly? It is fine when moving, but stop for a little bit and coolant comes out

I seemed to have trouble starting those big water cooled 500 two strokes so I can only speak to a 430 with quite restrictive guards on it. In hot weather arrowing for an enduro it boiled over and like you say getting some air through it cures it. It also boiled over at a stopper section where you either waited patiently in line or cut in front of someone else waiting in line. I can't say it ever did it real soon. Also I have a friend and ex riding buddy (ex due to medical issues) who bought one of those new and never heard stories of overheating problems. I find some of the water pump impellers shortened from rubbing which may or may not be an issue. Those radiators are small my modern standards and the impeller is tiny by modern standards but it must hold over a quart of coolant. I don't know if you could put the head (perhaps the gasket) on backwards or not I kind of have to stop and reason when deciding which way it goes.

Elaborated later, Just from memory, hopefully correct, last one I put together the head gasket didn't look exactly like the one in the parts sheet. It is designed so that only some of the passages will allow water flow between the cylinder and head. Since the hoses attach to the rear I put those passages in the head gasket toward the front to make the coolant more thouroughly circulate. If the gasket was put the other way or looked like the one in the picture the front which would seem to need the most cooling might not have a lot of circulation.

Fran

thanks again, fran. I haven't had the head yet. the radiators are pretty small though

hi talking about air flow through radiators , i recently bought a 88 wr430 which had been nipped up after a top end rebuild the problem was running it in on synthetic oil and not getting any air flow through the cooling system , a very good motorcyle mechanic said i should go and find a external fan and put on front of the the radiator and run it off the lighting system , i will look into it further , maybe someone on the forum might have already done this mod it would be good to share as this is a problem when sitting with engine running , thanks branchy

Hi Dave,

Just a thought and you probably checked this but do both your rads get hot? Also sometimes the impeller can shear which will mean no water flow. There is also a bleed screw on the side of the block. It may that you have an air lock. I drained my water system over the winter so I need to refill soon. Will let you know how that goes and if this happens to me.

Stu

good info, did not try the bleed screw yet

I appologize for hurting anybodys feelings. I get along with everyone, and my original post about the triple clamps was done in jest, but I do believe that some people need a little thicker skin. I'm sorry that you felt the need to police the post, I did call a truce

yeah good on you mate if its waffle and not helpful or interesting get rid of it why would someone waste everybody's time with it, if they want to get rid of a bit of time they can come to my place and help me cleanup the garage and service one of my bikes, i pay in cups of coffee maybe a pie or sausage sandwich and at the end of the day beer , branchy