muffler overheating 1971 commando

wkjohnson · Aug 21, 2013

I have a 1971 Commando Fastback longrange that has an overheating problem with the right exhaust. This happened after I had to replace the oil tubing between the two cylinder heads as they MELTED and leaked on both sides less than an hour apart. I replace with some rubber hose from a junk dealer as couldn't find the proper tubing ( I was out of town and wanted a quick fix so I could get back to the Island). On the way back the wiring to the right coil came loose so hobbled home on one cylinder. After fixing that and starting the bike up I found the right exhaust heating up very quickly - less than a minute.
I assume I have fuel burning in the cylinder. The exhaust coming out of the right muffler feels a wee bit stronger than the cool left.
Is this carburation or timing? or?

Rohan · Aug 21, 2013

If you are melting oil lines, then its not the muffler thats overheating ?!!

Sounds like it needs checking over by a good mechanic.
Start with checking the valve clearances, how much compression is in each cylinder, looking for airleaks, synchronized throttles and sticking autotiming mechanism.

concours · Aug 21, 2013

wkjohnson said:
I have a 1971 Commando Fastback longrange that has an overheating problem with the right exhaust. This happened after I had to replace the oil tubing between the two cylinder heads as they MELTED and leaked on both sides less than an hour apart. I replace with some rubber hose from a junk dealer as couldn't find the proper tubing ( I was out of town and wanted a quick fix so I could get back to the Island). On the way back the wiring to the right coil came loose so hobbled home on one cylinder. After fixing that and starting the bike up I found the right exhaust heating up very quickly - less than a minute.
I assume I have fuel burning in the cylinder. The exhaust coming out of the right muffler feels a wee bit stronger than the cool left.
Is this carburation or timing? or?

Hi, welcome. Points ignition still in place? Do a compression test and report the findings back here.

wkjohnson · Aug 21, 2013

It just came back from the mechanic prior to my trip. It will go back to him tomorrow. I don't want to overheat the bike on the way to the mechanic.

wkjohnson · Aug 21, 2013

Points look fine. Compression feels good when kicking over but I have no way way of measuring it.

pommie john · Aug 21, 2013

I would expect the exhaust to heat up within a minute.

Maybe the problem is that the other cylinder is not firing.

usefulidiot · Aug 21, 2013

i had the exact same problem with both melting oil lines and a cherry red right cylinder exhaust pipe. turned out to be an intake manifold leak on that side which created a lean condition on that cylinder. spray wd40 around the intake manifold junctions on that side while the bike is running. if the engine speeds up noticeably, manifold leak.

muffler overheating 1971 commando

wkjohnson

Rohan

concours

wkjohnson

wkjohnson

pommie john

usefulidiot

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