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replaced thermostatic fan switch about a month sgo, and fixed my overheating issues on short journeys

been using the bike fine, but as soon as i started riding around at 20/30 temp guage spikes - went to 3/4's today, but not into the red - but when i pulled over at home started pissing out coolant from the overflow tubes at the bottom of the fairing

any idea what this could be / how to fix it

bikes fine so long as it is at high speeds, doesnt get above halfway - its only at speeds uner 30 it starts to really heat up

thanks

reds

i no you say you have replaced the switch but does the fan cut in at the right temp?does the fan work if you short it out?
might be worth taking a look at the water pump make sure its circulating coolant

Worst case scenario:

I had this, and it was the headgasket.

nightmare !

as i said, was having a similar issue, but replaced thermo valve switch and it stopped it heating up really quickly.

however today within 1 mile of leaving the temp guage was up to 3/4's - if i stay above 60 it doesnt peak anymore, as soon as i go under 60 it starts to rise - went up to the red, so had to pull over to let it cool down

does this sound like head gasket ??? did a compression test a couple of weeks back, and the engine was just within the standard limit (105 psi) so dont know if it could be the head gasket, wouldnt it be considerably lower than the service limit if this had gone ???

think fan is next thing to test - how do i go about doing this ? is it in the manual ???

thanks

reds

ye im pretty sure its in the manual, you can 'short' the connector on the fan to make sure it works (it will just spin constantly)
but it seems to be heating up to quick for it to be the fan. i think someone on here had a similar problem and it turned out to be a blocked radiator so might be worth taking it off and giving it a good clean out with fresh coolant, dont forget to check the inline coolant filter (near the carbs) or possibly checking water pump is circulating the coolant.
hope this helps

try another compression test to be sure. A bike overheating so quickly is usually a good sign of a head gasket going, its also going to be easier to elliminate than taking everything off the bike to clean the cooling system. Obviously if thats ok then yes flush it out.

You can buy cooling system flush too so maybe worth using some of that to give it an extra good clean. http://www.wynnoil.co.uk/cooling_system.htm

checked fan at lunch time - shorted it and it works (even without the ignition turned on whihc i thought was a bit odd!) but it was definatly NOT on the other day when the engine got hot, as i would have heard it and didnt - going to recheck the connection of the thermo fan switch

It should come on with ignition off - When you stop it might be too hot, and need to cool

Sounds like HG to me....

ye it should do that but from what your saying it seems something more than the fan not cutting in even though it should be when its getting that hot, i would atleast be pulling the pipes off the rad and trying to flush it through atleast.
maybe even just run it up to temp stood still and see if the rad warms up and both in and out pipes are hot if the out pipe isnt means rad is blocked if both get hot means something else is wrong.....

thanks for all the input guys

this is the current update after a bit of fettling tonight:

FAN = working (when shorted) - however got bike up to 3/4's on temp guage and fan DIDNT kick in

THERMO FAN SWITCH = All correctly connected and only 2 weeks old - so cant see this being the issue

HEAD GASKET = I got the following readings from a cold engine (did warm but then had to rush out - so was cold when tested)
Valve 1 - 100psi
Valve 2 - 95psi
Valve 3 - 95psi
Valve 1 - 100psi
Not great ! but wouldnt have thought that such readings would signify a blown head gasket ?

RAD = when filling it up tonight with engine running (as per manual) was getting air bubbles come up - water seemed to be getting sucked down too - does this mean that the water pump is working ????

IN GENERAL
Bike is getting very hot very quick, within 2 miles it is 3/4's of the way up the guage
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So from the above i would imagine the next step is a rad flush with the stuff that rob recommended ???

did both pipes on the rad get hot when the temp was up?

those readings arent suggestive of a blown gasket no. So its either going to be a rad flush or the thermostat you got is as knackered as the last one.

thanks guys - will check the pipes tonight when i can take it on a longer run to warm up. and if that is teh case then flush the rad - if not i suppose its a case of taking everything off again to get to the thermostat and test that

@rob - i dont think it wil be the thermo fan switch - it was brand new for cradley (£40 worth!), not a second hand ebay job

sorry, i mean the thermostat which is what i wrote but not what you bought.

problem turned out to be dodgy connection to thermo fan switch - re-soldered it (instead of just having it clip on) and has been fine since now just need to sort out this rattle !!!