dandiddly Posted December 17, 2012 Report Share Posted December 17, 2012 Hi folks, My nephew is having intermittent trouble with his 08 125 Sherco. After about an hour of riding it will "boil over" and spit steam out of the radiator. When this happens he also seems to lose power. When we bought the bike the fan was wired to spin all the time and the thermostat was disconnected. Has any had any trouble similar to this in the past? I'm also struggling to find any kind of manual for a 2008 125 trials bike. The web site only seems to have a manual for the enduro bike? and the pinned link at the top of this forum doesn't list a 2008 125 either? I am new to the world of trials so maybe I'm missing a trick so any tips/links would be very much appreciated! Cheers, Dan Quote Link to comment Share on other sites More sharing options...
tirolean Posted December 17, 2012 Report Share Posted December 17, 2012 Did you have a look if there is enough cooling liquid in the radiator? Quote Link to comment Share on other sites More sharing options...
dandiddly Posted December 17, 2012 Author Report Share Posted December 17, 2012 Thanks for your reply. Yeah, we drained it all. Coolant looked in good condition, no scum or flakey bits! Replaced it with new stuff. Left the top hose off and filled in till it came out the hose hole, refitted the hose and added a little bit more. We originally had it filled to the top of the chamber on the top of the radiator, which i'm now assuming is an expansion tank? Any more idea's? Quote Link to comment Share on other sites More sharing options...
dombush Posted December 17, 2012 Report Share Posted December 17, 2012 (edited) Dan Firstly, its normal for a bike to lose power when it overheats. This is normally due to pre-ignition or worst case a partial seizure. Both issues are initialy minor but will turn terminal very quickly. A couple of questions:- The most obvious one is... was the fan running when it was boiling over? Were you travelling quite slowly (using it in sections for instance) when it boiled over? If the fan isnt working then the engine will most certainly overheat. This would be expected. My 07 125 will start its fan after 15-20 minutes use "in section" in the winter. Halve that time in the summer. If the fan wasnt running during the overheat then the most likely issue is a failed thermostatic switch or failed fan motor. Disconnect the fan from the thermostatic switch and wire the fan directly to a 12v battery to understand if the unit is faulty If the fan works, Unclip the thermostatic switch from its housing and withdraw. Rewire the thermostatic switch to a 12v battery and dunk the sensor end it into a cup boiling water. If the fan doesnt start after 30 secs then the thermostatic switch is the likely cause. My particular bike had a switch fitted to allow a rider to switch the fan on manually, this and your example are common mods for bikes that are used on road trials. It isnt beyond the realm of possibility that the thermostatic switch wasnt rewired correctly after trying to correct your modification. If the fan was working during the overheat there are a different set of possible causes. Let us know the outcome of the above first. As far as manuals are concerned, there is a "combined manual" due to the engines being very similar despite capacity differences. Look here http://www.sherco.com/EN/service_manuals.html under 2009 and download the "All 2 strokes trials models maintenance manual". I think this is the best information around. There are some other more detailed documents for specific procedures / issues. Dom Edited December 17, 2012 by dombush Quote Link to comment Share on other sites More sharing options...
copemech Posted December 18, 2012 Report Share Posted December 18, 2012 If the fan motor is not running on the bike, even with the thermo switch wires jumped together, yet runs normally when connected to a 12V external source, you may ck the voltage and such, but the rectifier is suspect. The fan will only run with rectified DC current supplied. Quote Link to comment Share on other sites More sharing options...
sectionone Posted December 18, 2012 Report Share Posted December 18, 2012 I had overheating problems even though the thermostat and fan were working. When the bike was new, the fan was very audible over the engine with a strong push of air. 5 years later the fan is quiet and pushes a gentle breeze. I replaced the fan motor and no more overheating. Quote Link to comment Share on other sites More sharing options...
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