Comer S60 max rpm & sprockets?????

[knighty]

Hi Folks - I'm running an old Comer S60 for my son for practice at Tilbury and I'm wondering what the max rpm of the older S60 is supposed to be???.....I know the newer W60 rev to 12,000.....but I suspect the older S60 does not, probably due to the old box exhaust......I also notice that in the early 90's there were only two sprocket sizes allowed, 80 and 85.....which I think is quite smaller than what people run on the W60.....were the S60 sprocket sizes generally smaller "back in the day" which I now understand is pre 2003!!

I'm currently running a 94 tooth sprocket which is probably why he keeps spinning it!!!.......have just fitted an 86 tooth, lets see how that goes, but would appreciate knowing the S60 max rpm.

[ghinzani]

I know the gearing there is pretty high - WTPs were in the 95 range. But then again you do run the risk of doing chains and sprockets on the bumps - might find for longevity of bits and engine then keeping it in the 80s might be best. Also good training as it means nipper will have to concentrate on momentum - never a bad thing!

[Rennen]

Originally Posted by knighty

Hi Folks - I'm running an old Comer S60 for my son for practice at Tilbury and I'm wondering what the max rpm of the older S60 is supposed to be???.....I know the newer W60 rev to 12,000.....but I suspect the older S60 does not, probably due to the old box exhaust......I also notice that in the early 90's there were only two sprocket sizes allowed, 80 and 85.....which I think is quite smaller than what people run on the W60.....were the S60 sprocket sizes generally smaller "back in the day" which I now understand is pre 2003!!

I'm currently running a 94 tooth sprocket which is probably why he keeps spinning it!!!.......have just fitted an 86 tooth, lets see how that goes, but would appreciate knowing the S60 max rpm.

Yes. we were originally restricted to just two axle Sprockets when the Cadet class started way back in 1987...90 for long tracks (Kimbolton etc) & 85 for twisty short tracks (Rye House etc) It was done to keep costs down! But we crafty dads just made split rims up to whatever width we wanted as Gearing...so that was more expensive than Sprokets in the end...so they gave in and let us change sprockets.

I've had a quick look in my old note books from our final year (1991) in Cadet and see we got 10,900 rpm with an 88 Sprocket at Rye House and 11,300 rpm also with an 88 Sprocket at Kimbolton...bear in mind I also still used differant wheel widths as gearing as well.

On the Dyno some of our front running competitors claimed in excess of 12,000 rpm. Our highest recorded were 11,900.

[Clive Brown]

Just out of interest, exactly how does altering the wheel width change the overall gearing? Tyre diameter I could understand, but width?

[knighty]

Originally Posted by Clive Brown

Just out of interest, exactly how does altering the wheel width change the overall gearing? Tyre diameter I could understand, but width?

if you run a narrow rim, it squashes the tyre into a bigger OD.......if you run a wider rim it reduces the OD, which has quite an effect to gearing if you are limited on sprocket sizes.........

Rennen - many thanks for that, are you sure you got that the right way around??? 85 for twisty tracks and 90 for long tracks......was the 90 a typo??.......did you mean 80 for long tracks and 85 for twisty tracks - I think thats what you meant???........right, so well over 11,000 then, that answers my question perfectly