100 Sport Sprocket size question

Looks to me like you have designed a new way to build a Sipper Clutch with that flogged-out front sprocket. Small front sprockets put a bigger load on chains making them contort more than a bigger sprocket. So you need to hear if the gearing works real world for engine power and decide on the possibility of maybe going bigger on the front and compensating with smaller on the rear. A good rule of thumb is 1 tooth on the front equals 3 on the rear. Finding sprockets that fit is a whole other ball game. Good luck.
 
Vince said:
Looks to me like you have designed a new way to build a Sipper Clutch with that flogged-out front sprocket. Small front sprockets put a bigger load on chains making them contort more than a bigger sprocket. So you need to hear if the gearing works real world for engine power and decide on the possibility of maybe going bigger on the front and compensating with smaller on the rear. A good rule of thumb is 1 tooth on the front equals 3 on the rear. Finding sprockets that fit is a whole other ball game. Good luck.
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Other way around, Vince. Bigger on the front and smaller on the back are the same thing ... higher gearing. Bigger front and bigger rear to compensate.
 
What I was saying is if you go up 1 tooth on the front and don't change the rear, that is the same or as close as dam it as not changing the front and going down 3 on the rear. Decades ago I put a 20 tooth front and a 34 rear on my 64 Bonnie, Std was 19+ 47, to gear it to the moon to keep up with more Modern bikes. That kinda worked, but it bearly pulled it. Yerr I think I wrote it wrong on that first post, it's been decades since I did that. Anyway, it's best to go as big as possible up front for chain issues.
 
If new - or good used - are not available it's quite feasible to retooth both.
At this end of the world I've done quite a few rarities
It's also an opportunity to change chain size - eg from the now odd 525 to the better modern 520

I'm sure someone in the UK used to advertise the service in Classic Bike mag.
 
Killerkel said:
Hey guys

My 1955 100 sport came with the following sprocket sizes:-

Rear 45
Front 13

My questions are, are they the correct sizes? And where can get hold of replacements ?View attachment 93633

Thank you Richard
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Hi Richard
My 75 sport and 100cc version has 45T and 13T sprockets.
Rebanding both sprockets is a good way to refurbish.
In the rear assembly, check that the drive pins are nice and tight also.
Cheers
Paul
Tasmania
 
Turn the front around, should be good for another 5000km. ;)

PM "Luigi" on here, he may have something suitable laying around.

More or less unobtanium, especially the rear. Re-toothing possibly the best/quickest/cheapest option.

piet
 
the front sprocket looks to be cmpletely flat (ie plate type) so making a new one would not be impossible as long as the internal spline is a stock broach size, teetyh cutting is taken as read, hardening process as well, not cheap, but probably a better way of getting a straight front sprocket instead of a wobbly one,, the rear has (realy) the only option of retoothing.
CLEM
 
The sizes of the sprockets are correct for the 100.

Some years ago I asked for a reproduction at a company close to cologne which is specialized on manufacturing sprockets.
The price which they asked was a fortune. Completely unrealistic.
Fortunatly I still own some which I bought of the late Cor Dees because even in Italy around Breganze not any is available.
Luigi
 
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