Motorcycle Repair: whats that noise?, honda cb125, nuts and bolts

Question
Hey Bill,
I got a 1974 honda CB125. While I'm riding, for seemingly no particular reason and at random times, I sometimes hear a rattling sound, something akin to metal grinding, that doesn't sound natural. Although the bike runs great, it's something I just don't want to see turn into a bigger problem.
I can't explain the noise. Like I said, it seems to happen randomly, in low gear, in high, usually when I'm on the throttle.
It sounds a little like something is loose, almost a creaking noise. It happens for a short period, then it goes away. I checked all visible nuts and bolts to make sure everything was secure. The noise hasn't gone away.
I took it to a mechanic in my neighborhood. This was about the time it sounded worst, or happened more frequently, usually when I let off the throttle. He took it for a quick ride, then told me it was the chain, which he tightened. Although it doesn't happen as often anymore, it still happens. Also, it happens so infrequently and sporadic that I can't be sure he fixed the same thing that I'm hearing. That said, anyway it could be the chain? Any other idea what that might be?
I got another quick question, one that the Honda dealership couldnt't answer. I'm looking for a kick start lever for my bike. I found a guy in Michigan (I'm in Los Angeles) whose got a kicker off of a 72 Honda SL 100. Any idea if that would fit my 74 CB125? Honda couldn't do a cross-reference, just a visual guess based on pictures. They look the same, but the part numbers are different. Please advise.
Thanks again for any info. It's a big help.
Adam

Answer
Adam, if the chain was too loose and the noise lessened, then it probabably has a loose spot in it that is still hitting either the swing arm or perhaps the chain guard.
Check the chain as you rotate the rear wheel and see if there is a really loose or tight spot in the tension. If so, then replace the chain and keep it lubed and adjusted regularly.

I'm wondering if the missing k/s lever is to do with some issues with the k/s mechanism inside the cases. There are some gears that will "grind" when the lever is pushed backwards, engine running and in extreme cases they will be partially engaged when there is no arm on the shaft. This will also make a grinding noise, intermittently.

I think the difference in the arms comes from the placement of the muffler. CBs are low and the arm must clear the muffler on the way down. SLs don't have that problem. Both should fit the shaft, however. Check with www.westernhillshonda.com for more assistance.

Bill Silver