CB500 twin - Overheating

[Fire99]

Hi gang,

Bit of a random one to throw out there. I've a 90's CB500 which by and large is normally as reliable as a very reliable watch but recently it's started overheating particularly the faster you ride.

I've checked the thermostat in a saucepan and that seems to open without too much fuss, and I've flushed and refilled the coolant.

Levels seem ok, coolant is still.....coolant colour and there is no emulsion on the oil dipstick.

Bike's done 39k but is 20 years old but I would have been surprised if the headgasket was causing problems on one of these.

Any thoughts?

Cheers much.

[Fire99]

Hi Guys,

It's had a coolant flush. Level remains pretty constant and doesn't use any or drop in level.

Normally it runs very cool on the temp gauge (a normal habit of this engine apparently) but recently the temp has been climbing even when cruising at say 70mph. The faster you cruise, the higher it climbs up the temperature gauge so there is definitely a problem.

I'm surprised since this engine is allegedly pretty bomb proof at 40k..

[Fire99]

Rubin215 said:

But is it actually overheating?

Does the needle end up in the red?

To be honest I back right off just before the needle hits the red (to protect the engine) but you can feel it is starting to run a bit rough by then so I'm pretty certain it is running very hot and this is just cruising down as low as 60.

Definitely a million miles higher than its normal operating temperature at those speeds (and higher).

[Fire99]

Thanks for the input guys.. Well gave the bike a bit of a run to get some heat into it. Got home and with the engine still running and the gauge showing fairly hot, the bottom of the radiator you could rest your finger on and the top of the radiator was lukewarm.

I squeezed the top rad hose and the temperature on the gauge rocketed..

Dead waterpump perhaps?