[RED]

I flushed the system, The thermostat is working ,fan is coming on. I just cannot figure it out.Any suggestions?
Thanks JIM

 

[1Adam12]

86 ZX900's were known to run hot. Is it going into the red zone? How long does it take to overheat? What is your mix of coolant and what kind are you using? One thing you can do is run water wetter with dionized water or distilled water and it will run a lot cooler. Use a higher mix of water (distilled or DI) if you are in a hot climate.

Spark plugs could be fouled or using the wrong type.

Oil could be too low, old, wrong type or possibly the filter by pass valve is blocked. Just buy a new one and you can check that off your list.

You may be running the bike lean and hence why it is running so hot - carb adjustment.

Your water pump could be history

Another possiblity is to check to make sure your valve clearances are set right as additional heat could be caused by the valves not in tolerance.

These are some of the things that could cause your bike to run hot.

 

[Curt]

Your water pump could be history

If you want to find out, one way to do it is to take off the radiator cap when the engine is cold, then start up the engine, let it warm up, and watch the coolant moving from the top hose into the radiator.

Another easier way is to feel your radiator when the engine is running and hot. The top of the radiator (or your upper hose) should be quite hot, and the lower part of the radiator (or your lower hose) should be a bit less hot. If neither one is hot, you're not circulating fluid. That is likely because of a failed water pump, but it could also be a clog in the system somewhere, especially the radiator. When radiators start to clog up, you'll only notice problems on a very hot day. When they get worse, you'll see problems all the time.
Curt

 

[Stuart]

Yes curt, that is the key, grap hot things, if they don't burn you, um, wait a little longer

 

[RED]

Thanks
RED