Crankshaft shock absorber

[56G80S]

Well, I got the crank sent away to Alpha Bearings. Second time in a week that service suppliers have been honest with me, I asked about balancing in view of the heavier modern piston and oversize pin but their view was probably not worth doing but if I want to waste money.......

The other one was Teasdale's at Northallerton. Too much to do to check the Yamaha valve shims myself (16k service) and their response, do it if you wish but have done many and never had to change them, always been sound at that mileage and if it starts well hot and cold (yes) but if you want to waste your money......

I see the 000830 CAM ENGINE SHOCK ABSORBER is in stock at AMOC Spares but not the 014021 CRANKSHAFT CAM SPROCKET. 21 TOOTH ENGINE & 21 TOOTH DYNAMO. Don't want old cam with new shaft, or old sprocket, so looks like more money going to Royal Mail getting supplies from more than one supplier.

Might go to 22 tooth and up a tooth on the gearbox output sprocket as I'm only 175lbs.

Johnny B

[chappers1962]

Well, I got the crank sent away to Alpha Bearings. Second time in a week that service suppliers have been honest with me, I asked about balancing in view of the heavier modern piston and oversize pin but their view was probably not worth doing but if I want to waste money.......

The other one was Teasdale's at Northallerton. Too much to do to check the Yamaha valve shims myself (16k service) and their response, do it if you wish but have done many and never had to change them, always been sound at that mileage and if it starts well hot and cold (yes) but if you want to waste your money......

I see the 000830 CAM ENGINE SHOCK ABSORBER is in stock at AMOC Spares but not the 014021 CRANKSHAFT CAM SPROCKET. 21 TOOTH ENGINE & 21 TOOTH DYNAMO. Don't want old cam with new shaft, or old sprocket, so looks like more money going to Royal Mail getting supplies from more than one supplier.

Might go to 22 tooth and up a tooth on the gearbox output sprocket as I'm only 175lbs.

Johnny B

I had to replace the drive shaft as the previous owner though that putting grease on the chain and omitting the oil, would be the perfect cure the leaky chain case problem. Changed the cam, as the internal splines were knackered, but the kept the sprocket as the teeth were in good condition.

[Mick D]

Hi

In my experience the only part of the shock absorber assembly to wear appreciably is the spline, If I were replacing the axle I would certainly replace the splined cam, I wouldn't consider replacing the sprocket unless the teeth or bore were worn.

Regards Mick

[clive]

I have experienced significant wear on the splined cam as well as the splines on the drive shaft. But then again this was using a fully laden double adult sidecar and I did manage to break off the worn splines on one occasion. Not much drive available! However even then the cam face did not seem to wear appreciably so I would not bother replacing the sprocket unless the teeth are knackered and I have not seen that on any of the many sprockets that I have laid hands on.

[56G80S]

Thanks for that. I'll check for bore wear on the sprocket but the whole assembly has had a hard and long life and I was thinking of replacing mating parts together.

But not into wasting cash either.

Johnny B

[Mick D]

I'll check for bore wear on the sprocket but the whole assembly has had a hard and long life and I was thinking of replacing mating parts together.

Hi

If the sprocket is worn to the extent it needs replacing you should also replace the primary chain and clutch basket as they really are mating parts. The cams on the sprocket and sleeve are far less critical.

Regards Mick

[clive]

I'll check for bore wear on the sprocket but the whole assembly has had a hard and long life and I was thinking of replacing mating parts together.

Hi

If the sprocket is worn to the extent it needs replacing you should also replace the primary chain and clutch basket as they really are mating parts. The cams on the sprocket and sleeve are far less critical.

Regards Mick

Bore wear on the sprocket? It only does about a 1/4 turn against the spring when first under load, once you are running it turns back and sits stationary compared to the shaft it is on.

[56G80S]

Clive, of course, that's what happens when I make snap replies on the 'phone, what a numpty! The sprocket tooth wear actually seems little, which surprises me.

I did always take care to keep oil in the primary case and chains in good adjustment even in the early days. Perhaps I'll keep the gearing "in" the primary case standard and go up a tooth on the gearbox output sprocket. Money saved.

Johnny B

[Pharisee]

Clive, of course, that's what happens when I make snap replies on the 'phone, what a numpty! The sprocket tooth wear actually seems little, which surprises me.

I did always take care to keep oil in the primary case and chains in good adjustment even in the early days. Perhaps I'll keep the gearing "in" the primary case standard and go up a tooth on the gearbox output sprocket. Money saved.

Johnny B

I've raised the gearing slightly on both my 500s. The '55 M18S has the normal 21 tooth engine sprocket, but runs a 17 tooth gearbox sprocket. It pulls that gearing quite happily. My G80CS has an 18 tooth engine sprocket as standard and had the 16 tooth gearbox sprocket. That meant that the gearing was 16% lower than the touring 500. As I wasn't going to use the bike for trials, the gearing was too low for normal road use. The engine sprocket was in very good condition (and expensive to replace) so I opted to put a bigger gearbox sprocket on. I fitted a 19 tooth sprocket which raised the gearing back to close to the touring ratio.
My '54 350 G3LS is a bit of a mixture of bits. That has the standard 18 tooth engine sprocket, but it has an AMC clutch and gearbox. The clutch basket has 2 less teeth on it compared to the Burman item, so the primary drive ratio is a little lower than standard. I fitted an 18 tooth gearbox sprocket to compensate and raise the overall gearing slightly.

[56G80S]

Thanks for that, Pharisee. Others actual experience is really helpful.

Johnny B