running hot still

I'm still having issues with overheating. After a short, not hard ride, I am started to loose power. I have done plug chops at several throttle ranges and am getting a dark brown almost black appearance on all parts of the plugs. Looking into the cylinder, the pistons are black and flakey looking. Compression is about 145 plus or minus a few per cylinder. What does this sound like to you all?

 

Your description of the plugs sounds the opposite of running hot. Your description of the dark brown almost black and black flakey appearance sounds like you are running rich and your plugs are starting to foul. I may be misunderstanding your description.

 

You read it correct. It smells rich also, but is getting way to hot.

 

How do you know that? How hot is it supposed to be and how are you measuring it?

 

Any chance you've got bad seals and you're burning more oil than usual? This is an air-cooled model, right?

 

When was last oil service and filter change, and what oil you running?

 

All oil seals are the original ones. It is air cooled. I am running Castrol 20w50 and a fram filter. It has only had one oil change since pulling it from the barn 600 miles ago.

 

And that's actual "motorcycle" oil, not conventional car motor oil, right?

 

It is motorcycle oil.

 

Good good, just making sure!

I'm currently stumped, but I figured those would be good questions to ask in case it helps spur something. So you're smelling the gas as it runs? There's no gas leaks coming from anywhere else? I'm just thinking what if the gas is leaking somewhere, making it run lean/hot. And the seals being old would make it easier for oil to burn up especially if it's too hot.

What about your exhaust... how's the smoke looking?

 

the only reason an air cooled engine would overheat is from not having enough air flowing over the fins on the head and cylinders or tight pistons/rings or lean condition. was the engine recently rebuilt? if so, it's possible the rings and or pistons were not properly fitted to the cylinders. your plugs could be lying to you where the fuel mixture is concerned. you need to do a proper "plug chop" to get an idea of what the carbs are doing. your brown or black color could be from the idle circuit. you might try a new set of plugs and run it down the highway for a few minutes then shut it off at speed and coast to the shoulder. then see what your plugs look like. it's possible the main fuel metering circuit is partially clogged causing the overheating.

CN

 

Just my 2c here:

What kind of gas are you running, regular or premium? Try premium, which is what i went to (canada has crappier regular gas).

Also sounds like you might have a fuel supply problem? is there an inline gas filter where you can see what is going into your carbs?

Sounds like compression is ok, valve clearances ok too?

 

When you start losing power during a ride, does it stall on you? What are you doing when this happens? Do you pull over and let it cool? And if so, is power regained again once you start riding again? The reason I ask, is maybe it has nothing to do with heat at all and your vent on your gas cap is clogged and causing a vacuum. Thereby, reduced flow to the carbs. If you think this is a possibility, open the gas cap when you pull over and you may hear the vacuum release. Easy thing to check and only take seconds to investigate. And if it does go back to normal power, a permanent fix easy.