Topic: Drive Sprocket Guard/Shield

[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. 

[mcpuffett]

hi, bob it depends on if the spare motor has mounts for the shield ,and before the problem of snapping chains there would'nt have been mountings for guards i think? but it sounds as though yours has had a engine case transplant to get one with no numbers.

[Bob Wessner]

Even the spare motor has bolts in the same places, but no guard. One of the bolts, nearest to the outside, is used for a retaining clip to keep a wire away from the sprocket. It seems as though the retrofit was to simply design the gaurd to utilize these two bolts.

[Hop on a Honda]

Bob.
I ordered one and the rubbing block 12 months ago, but when I tried to fit it, it was so tight  that the tollerance so close was almost 3MM Too tight The chain was replaced I took it back to Honda as well as the rubbing block on the little shaft.
I went back yesterday and there both gone.
Says NILL stock.
Dave

[Bob Wessner]

Not sure what the rubbing block is you refer to. I know there is not too much clearance between the chain and the guard (which has a strip of rubber-like material on the inner surface). I seem to recall reading the clearance was deliberately tight, theory being it would not allow the chain to bunch-up in there and just feed on through.. that was the theory anyway.

[cb750_chris]

Those bolts are probably case bolts that hold the thing together.  Holding the stator wire clip and chain protector are a secondary use for them. 

I wonder if the waranty case gan be given an engine # by someone with the right punches.

Any how.  If you plan on getting into the cylinders it would be a perfect time to get that free motor in shape.  No sense in getting into the cylinders if you arent going to freshen up the top end any ways.  The bottom end might only need cleaning, paint, swaping of the covers and some fresh gaskets.

The pistons/cylinders in that free motor might not be the same as the ones in the bike.  That would make fitting it's top end on the waranty motor a big job.  Best to hope for the top end only requiring to be honed and put it right back over the pistons it came off of with fresh rings.       

[Bob Wessner]

Correct on the bolts, they are among others, used to fasten upper and lower halves together, and as you say, just convenient fastening points for the chain guard.