Hi

I have a 1990 GK76a GSXR 400 and have noticed something which I believe could become a problem. So far, the bike is working fine and runs well.

When the engine is hot I've noticed that coolant comes out the overflow pipe under the bike. Does anyone have any idea what could be the problem?

There is no excessive smoke from the exhaust so I don't think its the head gasket. I topped up the coolant as I was unsure how much could have been lost. I got the bike hot again and coolant ran out like it was overflowing again.

Thermostat not working properly?

Has anyone experienced this problem or know what it could be?

It is supposed to come out when it is hot. If it is doing it when not very hot then suspect your radiator cap is not working well enough to pressurise the system.

First swap the rad cap as it's the cheapest thing to try, if it's not pressurising the system it will boil the coolent real fast. It could be the stat is stuck shut meaning you have no radiator cooling or it's the dreaded head gasket.
Also make sure you have no air locks in the system, there is a small bleed screw on the left side metal coolent pipe you can undo to let air out and you should squeeze the pipes to force any bubbles out.

Thankyou for your replys chaps.

I have had the bike about 4 months and had not noticed this before. I had no idea its meant to spit coolant out the overflow pipe when hot.

I'll follow your suggestions and try and have a look at it again over the weekend. Its the thought of messing about a freezing garage that puts me off.