86 VFR 750 gets to hot zone quickly?

Riding around town, getting stuck at a light here and there and as I look over, goes to the hot zone rather quickly. I thought maybe a possible stuck thermostat but not sure. I'm not even sure if the fan kicks on. I really can't hear the fan or know that's it's on because of the exhaust noise. If I'm able to get in some open lanes and go, I can get it to go back to half way. It's seems that once I shut it down, it doesn't go back to the hot area for the rest of the night? Thanks, Mark

 

Does the radiator get hot? If so, make sure the fan is running. It won't make much noise, just feel for air blowing through it. If not, bad thermostat or bad radiator cap?

 

I concur with EVT, however I dont believe its a bad thermostat because you say once it goes thru a heat cycle it runs within temp. I might be looking at a dirty cooling system, maybe a pinched hose, possibly a leaky rad. cap and last but not least a partially filled cooling system. eddie

 

I guess I'll pull off the side panel and check the fluid level. I had just purchased it and believed that the guy who had it before kept his levels up but maybe not. If it's up to level, I'll check to see if there is an over flow bottle located on the bike somewhere and it may need some to draw from when hot. I'll check for a breeze from the fan and then check cap. thanks, Mark

 

Mine had a similar issue When I got it turned out to be a radiator cap not put on correctly

 

The bike pushes coolant OUT when hot, pulls it IN when cooling down. Don't fill it above the high line on the overflow tank when cold or it'll spew out everywhere when it gets hot.

 

my bike did the same ('86 700). Found LOTS of air in the cooling system. When I last did a coolant change (possibly it's first in a decade), the radiator cap ended up with a cracked seal.

What I've done to the bike since buying mine in Dec is:

- full drain of the cooling system (both front plugs and the pump drain)
- refill with 50/50 distilled water and distilled white vinegar
- heat cycle
- drain fully again
- flush with distilled water
- fill with distilled water
- heat cycle
- drain
- fill with premix coolant (I used Engine Ice)

Now that I took care of the air leak at the cap (it was pushing out coolant into the bottle, but sucking air in around the cap when cooling off), the cooling system works like a champ.

On a cold day, you know it, the engine stays nice and cool. On a hot day, the fan only comes on when stopped, or going slow up a STEEP incline (1st gear, 2500rpm, 10-20% grade).

Definitely pull and inspect the radiator cap, and make sure there's no air under it. My coolant bottle was right on the mark, and there was a quart of air in the cooling system.

 

First chance I get I'm pulling my cap for a visual. I have been riding on cooler nights and go figure, it stays towards the middle all the time. The biggest factor with the red zone area is going slow light to light and stopping. Rises quicker in the city. Highway speed brings it right to normal.

 

I agree with all of the above. Just make sure the rad itself isn't partially blocked with excess bugs and road grime. Reduced airflow over the rads will easily over heat these little radiators.

 

Make sure your fan is running when it gets hot. I put a switch on mine so I can turn it on and off whenever I want. It should get hotter at lights and in slow traffic, but the fan should keep it in check.