A friend of mine has a trike, its a cx500. He has a problem with it over heating, we've flushed the system, cleared the muck from the rad, tried another thermostat, even ran it without a thermostat. The water pump is working and the rad fan is too, we're now at the pulling hair out and wacking it with a lump hammer stage, any suggestions anyone please

isn't running way lean is it? if water pump is fine, rads getting hot and fans are working, then its another logical solution.... that or poss head gasket. is it loosing water or pressureising?                                                                                                                                                                              

seam to remember cx500's having water pump problems  but its along time ago since i looked at one of them engines                                                                                                                                                                              

does the engine overheat quickly or slowly?if its not losing water probable fault is a blocked rad,it only has to be blocked about10%,and it overheat,try another rad and see if it still overheats.                                                                                                                                                                             

Is it a replacement engine of unknown origins or been left standing? Were there any other symptoms? If its been run without anti freeze the radiator, block or heads could be blocked or coroded internally, if its been stood inactive for along period other corosion or oil seal damage may have occoured.

This maybe a silly question,but how do you know it`s overheating?
Is it blowing coolant out? Or is the temp gauge(can`t remember if the CX was fitted with one)reading high-could just be a faulty sender unit.
                                                                                                                                                                             

Nealy's right, I recall from my time as a parts/warranty guy at a Honda main dealer that CX's had a lot of problems with the water pump impellor and seal. I also recall that they never really sorted the problem despite about 5 supercessions to the parts involved so most long term owners just went with replacing the affected bits on a regular basis.

Done a bit of work around Trikes
Standard bike radiators are very stressed because the engine is having to wok much harder fro a given speed than in the original 2 wheeled configuration

CX500 uses a mechanical fan driven from the cam shaft the plastic fan have been known to be loose on the  alloy bush witch fits the shaft
The ugly duct work around the radiator is important many trike builders remove it and you can get reduced cooling !

I would check the fan is tight to the shaft that the raditor is clean externly so you are getting a good flow of air though it

On a trike you may need to go to a larger radiator or additional electric fans to keep it all cool

A good test is to check that the trike will idle on the spot for a quarter of an hour at least

I would use an infered thermoniter to see what tempature verious bits get to the radiator should not exceed 110c
(remember water at pressure boile at a higher temperature !) system pressure should reach 1.1 / 1.5 bar above normal (printed on pressure cap )