BrianK said:
Good to know re the ATF, thanks Bill.
How many miles on that primary chain? Did it give any warning, or just go? Do any damage? (He asked, fearing the answer....)
My primary chain failed without warning. I was traveling down I-95 in southern Palm Beach County, about 10:30 at night, and doing about 4500 RPM. Nobody was on the road within a 1/2 mile of me, and the highway is 5 lanes wide at that point. I rolled on a little more throttle, and at just about 5000 RPM, I heard a distinct metallic 'tink', and the motor started revving freely. I figured I had thrown the drive chain, and coasted over to the side of the road. I put the bike on its center stand, and saw the chain was still on. Shutting the bike off, I ran the tranny through the gears while spinning the rear tire, and got almost no resistance. Figured at that point I had either snapped the main shaft on the tranny or broke the primary chain. As far as I know, the chain was original to the bike, which sat, disassembled, in various garages for over 20 years before I got it.
Once the bike was home, I found the primary chain neatly piled between the two pulleys in the case. No damage to the case, the pulleys, or the stator. Inspection of the chain showed one of the plates had apparently failed, as the edge of the break did not look new. Two other plates on that same link had fresh breaks at the same point - the thinnest part of the plate, at the top and bottom of the pin hole. The last plate was intact but deformed, having pulled off of the end of the pin.
I thought I was real lucky, having the chain be the only damage, but analysis of the system would show that the most stress is at the point where the chain comes off the clutch drum. While on either pulley, the load is spread over all of the rollers on the pulley, and the bottom loop of the chain is slack. It is only when the chain comes off the clutch drum that the row of links goes from a distributed load to a direct load, and is the most likely point where failure would occur. I think it would be pretty rare for a primary chain to cause damage to the crank or crank case, though I could see where the chain could end up wrapping around the clutch drum and damaging the primary case or transmission.