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Hi Sir,

I am a youth trials rider in England. Every time I rev my bike the fan comes on and when I let the revs off the fan goes off. The bike feels to be getting too hot. I then realised my gear oil was very low. Please could you tell me if this might be why my engine was getting very hot and causing my fan to be going on and of every time I revved my bike. Please could you help.



The low gear oil may have contributed to the engine heat, which in turn would cause the fan to come into operation. The fan is controlled by a thermostat in the coolant hose connection. It normally should come on once in a while when the engine needs cooling down, but should not work in conjunction with the throttle opening or closing.

My first guess is that the bearings in the fan lack lubrication and/or the connections to the fan are corroded to the point where it takes a more than normal amount of electricity to cause the fan to operate (to overcome the resistance). There is also the remote possibility that the electrical generating system for the fan is not producing enough output at low RPM's. Opening the throttle would up the output of the electrical system, which in turn would be enough to overcome the resistance and the fan would go on. Closing the throttle would have the opposite effect.

I'd take the fan off and check it over and try to add some lubrication to the bearings by spraying the bearing area with a light lubricant. I'd then take all the electrical connections apart, scrape or clean them, spray them with contact cleaner and when dry, assemble them with some dielectric tune-up grease to avoid corrosion in the future. Dielectric grease can be obtained at an auto supply store, it's used to lubricate wires on sparkplugs and distributer caps.

Give this a try and be sure to contact me if you need further help, Karl.


Professional tuner and 'Trials Competition' writer Jon Stoodley has very kindly stepped up to the plate to answer your questions. If you're having problems, or need some advice just send an email to Jon. If it's something that could be useful to others, we'll post it on the site.
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