87 Yamaha Moto 4

[tgag78]

I just picked up the 87 Yamaha Moto four. Started off fine with no issues. I change the exhaust pipe and now it seems like the motor head gets really hot and starts to fume. This happens approximately after eight or 10 minutes of idle or low speed riding. There's no colored fumes from the exhaust Itself. I added more oil to the engine prior to starting obviously. I was wondering if there's any way to know if the engine is overheating. Please note that this is an oil cooled engine. Any ideas or thoughts are welcome. Thank you

 

[maim]

actually it is an oil/air cooled motor.

did you replace the exhaust with another stocker or an aftermarket one?

if you replaced with an aftermarket, it might need more gas which means larger jets in the carb.

also check the valve covers as the gaskets can fail and it can drip oil onto the exhaust.

 

[tgag78]

Stock exhaust pipe. No leak visible in reference to the gaskets. I'm just wondering if this is normal heat being generated or pathological.... How would I tell the engine is overheating?

 

[devinzz1]

what size engine are we talking about here?

 

[tgag78]

350cc, I looked at the spark plug, def not rich, if anything on the lean side, how would one adjust air/fuel mix on these carbs?

 

[devinzz1]

350cc, I looked at the spark plug, def not rich, if anything on the lean side, how would one adjust air/fuel mix on these carbs?

On a 4 stroke you really cant read the plugs to good but if its lean it would be running hot. there should be an air screw or fuel screw on the side of carb.

 

[tgag78]

Will attempt at finding this adjustment screw...
Thank you for your help!

 

[maim]

check the carb boot where it connects to the head as well. they come apart an cause the same problem.

 

[devinzz1]

check the carb boot where it connects to the head as well. they come apart an cause the same problem.

on the big bear 350 the carb boot was a big problem and many aftermarket companies make ones that fix the cracking problem. I only have experience with the little 80 and 100 moto 4's and the big bears.

 

[tgag78]

Thanks guys, much appreciated!