Overheating Question

My 1980 R65 has one head getting hotter than the other. Carbs were rebuilt and sync at idle. but when the throttle is applied there is a drastic change / difference. I checked compression, adjusted valves and confirmed there werent blockages in airsupply or exhaust.

Am I missing something simple?

trianything1 said:

My 1980 R65 has one head getting hotter than the other. Carbs were rebuilt and sync at idle. but when the throttle is applied there is a drastic change / difference. I checked compression, adjusted valves and confirmed there werent blockages in airsupply or exhaust.

Am I missing something simple?

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Did you also synch off idle, that is, with throttle twisted a tad?

Welcome to the forum! Carbs were rebuilt and are you sure that the needles are positioned the same? I don't know the setting off hand, but usually what you can do is measure the amount of exposed needle to be sure they're the same amount.

You could also have a leak creating a lean situation. Try spraying the carbs with something like brake cleaner and see if the RPMs change while at idle. Maybe the carb-to-head rubbers are cracked or a clamp is not tight?

Also make sure that the carb enricheners are completely off.

Thank you,

I plan to run down he list of all your suggestions.

I replaced one pin due to pitting. I will be disappointed if I placed it wrong but very happy io get her up and on the road.



Much obliged.

Carbs "rebuilt" MUST include new diaphragms. Should include new needles, as they wear. (Fuel/air mixture is abrasive.) When the needles are both set the same height, THEN it's time to synchronize at 4K rpm.

Change in temp between the cylinders indicates cables are not in synch above idle.

Even with all the carb syncing don’t expect the cylinders to be the same temperature. With my experience on aircraft engines very seldom do you have cylinders the same temperatures in CHT’s and EGT’s. On a motorcycle the direction of the wind should have a factor on the cylinder temps LH to RH cylinders.