How do you know if your FJ (or any air-cooled motor) is overheating?

[Bminder]

It's pretty warm here in Cheyenne today (90... haha) and I was downtown looking for a business, slow (under 15 mph,) stoplight to stoplight, no wind. I could feel the heat from the bike more than normal. Still ran great, but started to idle in the 1600 range instead of 1100.
So I got to wondering how would I know if the motor was overheating? What are the signs? What do you need to do to avoid it?
Can you just shut it off to cool down?

[Paul1965]

Personally I go by oil temp using a TTO oil temp gauge just like this: http://www.trailtech.net/digital-gauges/tto/722-es2

You can also buy cylinder head temp gauges that fit in-between the cooling fins on the heads, but usually you won't be able to see the gauge when you're riding.

As far as signs of overheating, sometimes you'll hear pretty loud popping/pinging noises from the engine itself as the metal expands. It will also very difficult to start right away after shutting it off (the starter will drag similar to if the battery was low). Once they're hot the only thing you can do is get out of traffic where you can ride to cool it down or just pull over and shut it down for a while. Never hit a hot engine with water in an attempt to cool it down, you'll probably just end up cracking a head or worse the case.

Just my 2 cents worth, hope it helps.

[Pat Conlon]

I don't care for having a oil temp gauge. I don't care to see how hot my oil is....I really don't want to know. It would just freak me out.

I know my FJ gets hot from time to time. I try to avoid it, but sometimes it just can't be helped.
Crossing the desert, I had it so hot, that the gas tank scalded the inside of my thighs.

I try never to shut my bike off when she's hot...until I can ride for a 3-5 miles, uninterrupted, at 30-40 mph to cool the bike down.
Even if it means taking the time for a couple of extra trips around the block.

Heat mitigation for me, is all about
1) proper airflow
2) proper jetting
3) High efficiency oil cooler.
4) clean, fresh 20w-50 oil

It's 110* in the desert today....Oh, but it's a dry heat...(yea well, so is my oven )

I'm glad I'm at the beach.

[Paul1965]

I don't care for having a oil temp gauge. I don't care to see how hot my oil is....I really don't want to know. It would just freak me out.

Actually Pat, you'd be surprised how cool the oil really is. On an average day (for me anyway), I see oil temps around 200-215. One of the highest temps I've seen was just last week when I was stuck in traffic on a very hot day, and that was 260. 

[yamaha fj rider]

When stuck in traffic, your FJ will let you know when it is getting too hot and is unhappy. Running ruff, noisy, if you are paying attention she will tell you. 

Yesterday mine was getting hot in the mountains on a ride with some local sport bike riding group. One of the fellows commented that my bike was smoking some. Lots of throttle, going up hill, about 95 degrees F, 7,000 plus rpm's. I have been running the 5-40 Rotella oil. I was thinking about going back to a 20-50 oil, after reading Pat's comments about 20-50 and others I have spoken to or PM with. I think I am sold. Just think that the lighter oil causes it to smoke a little when it is working hard and getting hot. JMO. Hope this helps.

Kurt

[Bminder]

Yeah the lighter oil is probably getting past the rings when it gets that hot.
I don't know if mine was getting too hot, but I noticed the idle rpms were up and I could feel it on my legs more than usual.  Power was the same.

[yamaha fj rider]

That is what I am thinking. Oil to thin when it gets that hot. Changing oil in the next day or two.

When it gets very hot you will know. Lots of heat coming off the engine. Really running ruff, and loud. If this happens you will know it is hot. I think you were fine.

Kurt