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Drive Sprocket Guard/Shield

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Bob Wessner:
I’m in the process of fitting a new chain to my ’69 750. The frame VIN is 1017898. The motor has always been something of a question. It appears to be correct in other ways, but the area that should have a number is blank. While fitting the chain, I removed the drive sprocket cover and found one of those shields that is supposed to help prevent holing the lower case in the event the chain snaps. Out of curiosity, I checked a spare motor I have (VIN 1016746) and it does not have this guard. I don’t believe they started routinely installing the guards until the 20,000’s somewhere. My question is, if the lower case had been holed some time and replaced, might the dealer have retrofitted one of the guards/shields

cb750_chris:
Sounds like the dealer gave that bike a whole new case.  The replacement case would have no numbers and would already have that extra guard instaled.  The extra motor you have sounds like a good original motor if you were so inclined to take that waranty replacement motor out. 

Bob Wessner:
The idea for the spare motor, which was free, was to use the cylinders down the road because I have a chip out of a fin on the orig that's on the bike, as well as possibly a "training motor" given that I still have my training wheels on as far as wrenching goes. I don't know what the overall internal condition of the spare is, it, according to the speedo on the bike it came from had 25,000 miles on it and I have to say the external appearance suggests it may not have had an easy life.

Mark M:
25K miles is not a lot for these motors, it's appearance could probably be cleaned up fairly easily, damage is more difficult. Signs of oil leeks and a compression test are where I would start.

Bob Wessner:
One of the previous owners had all the covers he/she could get their hands on chromed and not a good job. Pealing and cracking all over the place. I agree about the miles, just have this feeling. Guess I will find out if/when I get into it down the road. Fortunately, the cylinders and head seem to be pretty good, at least externally. It certainly wasn't stored very well, not that I'm one to talk on that score, but even worse than I did with mine.  ;)

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