Hello, I have a 1993 Yamaha big bear 350, it runs good when we are out in the hills, but I notice it gets really hot after a while. Much hotter than it should be getting especially in the cooler weather we have had. I’ve cleaned off any dirt on the motor in hopes that would be it it but it isn’t. The motor gets so hot the gas vent tube starts to spit a little gas out sometimes. What could this possibly be? I keep up on the oil changes, and run regular unleaded gas. Trying to figure this out now, because I know when it heats up in the summer I’m probably not going to be able to ride it. Any advice is appreciated!

thank you

 

I do not have, nor have ever had that bike. However, if it were me, I'd make sure the oil cooler is as clean as possible and I'd be checking the spark plug for a lean condition. Compare your pulled spark plug to an online spark plug color chart. Even better would be to replace the spark plug, run it for a little bit, pull the plug and compare to the chart. Too much air and not enough fuel could cause a lean condition which will result in a much hotter engine. That is not good for the reliability of an engine.

 

I appreciate the advice! I put a new plug in about 2 mo the ago, I will pull it and see what it looks like since I’ve been riding it a lot since then. I did put a new carb on it a while back, so that could be a option running to lean. It sat for many years before I did all of this and got it going again, and never once gave a thought to the oil cooler. Did not know that was a thing with cleaning it out. I’ll have to do some research on how to do that. I sure appreciate the help.

 

To add.. I also think I need to get a quality carburetor. This newer one I have is one of those really cheap ones I bought off of amazon. I think that might be the thing that is giving me issues.

 

There are definitely parts on Yamaha bikes where you don't want to buy cheaper aftermarket parts. I would say carbs or carb rebuild kits would be one of those parts.

If the running hotter is only known to be happening after the carb was replaced, then you seem headed in the right direction based on your last post.

 

Your plug should be a coffee color or darker, lite tan or white is to lean! Oil cooler looks like a small radiator, blow thru it or blast it with a garden hose. Consider using a full synthetic oil as heat wont bother it like it will dino oil. I run only full synthetic oil in aircooled engines in summer heat. Syn oil will dissapate heat more quickly.