bounce Report post Posted May 1, 2016 My bike started overheating for no apparent reason on the last few rides out and I don't know why. It starts and runs fine but when I try to hill climb or give it some big licks it starts to spew steam out of the rad over flow pipe. The fan has always seemed to like coming on and that's not changed, the coolant level drops even if it's not overheating but isn't entering the gearbox because my oil if fine, I've let it run on tick over with a few blasts on the throttle (in the back garden, the bike is clean) to bring it up to a temperature where the fan comes on trying to find a leak on any pipes but there isn't any. Can anyone help? Thanks in advance. Quote Share this post Link to post Share on other sites
glynn Report post Posted May 1, 2016 Is the water pump propeller okay and spinning? Quote Share this post Link to post Share on other sites
spen Report post Posted May 1, 2016 Slight leak in the head gasket?? Quote Share this post Link to post Share on other sites
bounce Report post Posted May 1, 2016 Thanks for the replies Glynn - yes water pumps working fine Oni nou - all fins on the radiator are clear no bent fins or anything Spen - I have thought about this , but how would you know? Is there a possibility it could be anything else? Quote Share this post Link to post Share on other sites
spen Report post Posted May 1, 2016 If you've got a bit of a leak on the gasket, this can cause the cooling system to pressurise and force coolant out as you describe, any air finding it's way in to the cylinder can weaken the fuel/air mixture casing overheating. Quote Share this post Link to post Share on other sites
spen Report post Posted May 1, 2016 Also, have a look at the operation of the thermostat, is it staying shut when it should be opening? Quote Share this post Link to post Share on other sites
mazz46 Report post Posted May 1, 2016 Don't think they have thermostats my be wrong? Quote Share this post Link to post Share on other sites
spen Report post Posted May 1, 2016 Never taken one apart, so don't know...... Quote Share this post Link to post Share on other sites
worldtrialchamp Report post Posted May 1, 2016 is the radiator cap maintaining pressure...you've got to eliminate all the basics. ...get a mechanic Quote Share this post Link to post Share on other sites
dadof2 Report post Posted May 1, 2016 Cylinder head joint leaking? Rubber on radiator cap perishing or thinning? Kinked hose or inside of hose coming away reducing coolant flow? Give he radiator a thorough clean inside and out. Check plug colour - has mixture gone weak for some reason? Put a strobe on the ignition, sometimes CDI partial failure can give incorrect timing that causes overheating. Quote Share this post Link to post Share on other sites
bilks Report post Posted May 1, 2016 (edited) They have a thermo switch but if your fans kicking in and out it's working,you say your water pumps working,have you removed the case to check it operating properly. Edited May 1, 2016 by bilks Quote Share this post Link to post Share on other sites
crazybond700 Report post Posted May 2, 2016 (edited) Don't think they have thermostats my be wrong? Its only a sensor for the fan. IMO if the fan does not work, or the waterpump doesnt, it would overheat quite fast standing in your garden. You can check if the fan turns at the moment its trowing out coolant. But I think all the suggestions have been given so check it all out. Headgasket Leak in radiator (but would cause dripping somewhere) Faulty radiator cap Waterpump (leaking waterpump would not cause overheating) Fan not working propperly (maybe try to measure the voltage of the system) Thermo switch. Edited May 2, 2016 by crazybond700 Quote Share this post Link to post Share on other sites
