PD: Primary Drive Rapide Chain Problem

[bmetcalf]

I went out for a ride the other day and could hear noises from the engine. It wasn't regular and the bike felt as strong as ever, so I didn't park it and just rode home. When checking it, the motor rotated, then would turn further. This was sounding expensive, so I took off the timing cover, tank, UFM, and heads to see how the crank was. It turned easily with a spanner on the half time pinion nut until a certain point, so to the primary side. I found a bit of a mess:

Time for a new chain, blade, dynamo sprocket, and ESA springs! The old sprocket was firmly in place, so that didn't cause the chain damage, it was just the rollers starting to fail. As usual, I can't remember when I installed that chain, but I'll look at my receipts and see if I saved that one. I have some sort of modified ESA with a spring count somewhere between a C and a D. Only 3 or 4 look broken, but it seems prudent to put in an all new set.

The sounds I heard were probably individual rollers popping off. I think I'll try a delrin(?) dynamo sprocket to provide a weaker link

 

[Bill Thomas]

Strange how some of the teeth still look OK,
If too much in mesh, I would have thought they would all be worn ?.
Good Luck, Bill.

 

[greg brillus]

The chain rollers would have failed, and thus taken out the sprocket. On the plastic sprockets, the teeth are wider not machined down slightly like the steel ones........these will fail if the chainwheel bushes show too much slop causing too much sideways movement.

 

[stumpy lord]

I went out for a ride the other day and could hear noises from the engine. It wasn't regular and the bike felt as strong as ever, so I didn't park it and just rode home. When checking it, the motor rotated, then would turn further. This was sounding expensive, so I took off the timing cover, tank, UFM, and heads to see how the crank was. It turned easily with a spanner on the half time pinion nut until a certain point, so to the primary side. I found a bit of a mess:

View attachment 49951

View attachment 49952View attachment 49953


Time for a new chain, blade, dynamo sprocket, and ESA springs! The old sprocket was firmly in place, so that didn't cause the chain damage, it was just the rollers starting to fail. As usual, I can't remember when I installed that chain, but I'll look at my receipts and see if I saved that one. I have some sort of modified ESA with a spring count somewhere between a C and a D. Only 3 or 4 look broken, but it seems prudent to put in an all new set.

The sounds I heard were probably individual rollers popping off. I think I'll try a delrin(?) dynamo sprocket to provide a weaker link

HI,
you were very lucky, if the chain had broke, they have a tendency to come out through the front of the primary case, a very expensive thing to have happened as my son found out.
stumpy lord

 

[bmetcalf]

Strange how some of the teeth still look OK,
If too much in mesh, I would have thought they would all be worn ?.
Good Luck, Bill.

I rotate the Alton to have good mesh.

 

[Bill Thomas]

Those Alton's are hard to turn ?,
I am hoping my Mcdougleator with a slipper clutch, Is a bit more kind to the chain ?.
Cheers Bill.

 

[Peter Holmes]

Walkernator with Nippon Denso Alternator will solve most of your alternator drive problems, but you will have to wait for Norman to recover from his knee replacement surgery first, no slipper clutch required and hopefully no disproportionate stress on the middle row of the primary chain, the alternator is driven by a multi vee belt, which hopefully would operate a bit like a rubber shear pin or safety device, but as Gregg states, not if your primary chainwheel is slopping around.

 

[chankly bore]

I'm probably wrong here, Bruce, but I recall hearing that later Renold chains had rollers that were formed from flat, rather than the solid round rollers that were made in ancient times, and which Tsubaki chains still possess. Was this your problem?

 

[bmetcalf]

Welded vs. seamless rollers has been a controversy for quite a while. Whitakerpedia has several MPH articles on it. I'll look at the rollers to see if there are any clues. In any event, I'll get the new chain from a trusted source.

 

[Vincent Brake]

Nice, just wrecking your vinnie, cos you can.

Some say: to take it apart until broken.

I always say better check it...