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My Project M72.


Eastwest
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Sounds good!

Thanks, starting 2nd or 3rd kick from cold at the moment. Ironing out the bugs. The left cylinder runs hotter (better?) than the right. I am sure the mechanic can sort it. He is 'old school' and moves around the bike like and old friend, even though he has never seen this make/model. The bike looks much better in the pics...60 years of use is showing but i will preserve her rather than restore. That wear and tear has a charm of it's own....well I tell myself that.
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Hey,

 

If the left is hotter I'd think that the carbs need balancing.. However this is not really an exact science in my experience.

I've used one of those optical thermometers a bit and it seems the temperature on my cylinders are changing quite a bit.

One day left is 20c hotter, next day it's the right one.. Most of the time they seem to be around 200c, the heads measure a bit less.

 

I do think that this optical measurement is a bit untrustworthy since it seems to be very dependent on what kind of material you point it at..

Doesn't make sense to me that a bolt in the final drive would be warmer than the rest of the final drive for instance.. ;)

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Hey,

 

If the left is hotter I'd think that the carbs need balancing.. However this is not really an exact science in my experience.

I've used one of those optical thermometers a bit and it seems the temperature on my cylinders are changing quite a bit.

One day left is 20c hotter, next day it's the right one.. Most of the time they seem to be around 200c, the heads measure a bit less.

 

I do think that this optical measurement is a bit untrustworthy since it seems to be very dependent on what kind of material you point it at..

Doesn't make sense to me that a bolt in the final drive would be warmer than the rest of the final drive for instance.. ;)

Pressure coming from the exhaust is much stronger on the left too. Anyway.. i will see what the mechanic can find. I admire you guys who are mechanically minded.
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  • 2 weeks later...
bike is running well...lots of frustration along the way. We put the old original carbs back on and she runs better with them... :) Changed the gearbox only to find the kick start now hits the foot peg.. i guess i have to have it cut and shortened. :(
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  • 2 weeks later...

Update. We experienced rough idling and stalling. The mechanic removed the K68 carbs and took out the brass floats. He replaced them with the plastic ones from the cheap Chinese carbs. Here is the latest pic of her running. Very happy..it’s the best so far.

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  • 1 month later...

Perfectly normal for the left cylinder head to run as much as 30 degrees hotter then the right. That's why there is a separate oil supply running off the main gallery to the left side just for the left bore. Same with earlier BMWs, up to the late 1950's. It all has to do with oil spray from the rotating crank. Just make sure if you pull the left jug you don't cover the oil outlet with the new gasket. Also, if memory serves right, there may have been a field modification about drilling 3 holes in the left piston skirt ro allow excess oil to further lubricate the bore. Of course, if you do that, the pistons would be out of balance. You need to further research that mod.

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