Anyone changed the rear sprocket ? I have been told that aftermarket 4 bolt sprockets need some sort of machining to fit ? what needs to be done ?

Also anyone know if a 44 rear sprocket will fit onto a std chain ?

I think S3 have a compatible sprocket in their catalogue.

We've put a 10T front sprocket onto Dad's bike - I prefer the standard gearing myself but he likes it lower so he doesn't have to ride the clutch so much.

is there a big difference from a 11 to a 10 when comparing bikes ?

Yes there is - the one tooth at the front is something like 9% reduction in the gearing. Dad prefers it because the motor is revving more, the bike is harder to stall so he doesn't have to be so quick on the clutch. He can ride it through some sections without covering the clutch, whereas I have one finger on the clutch all the time. Dad still seemed to get up all the big stuff last weekend without going into 2nd gear, bike was just revving a little harder.

I prefer the standard gearing myself but Dad is a lot happier with it geared lower. I was a bit worried that the lower gearing might make it a bit angry and agressive to ride but thats not the case, the power delivery is still very smooth and not agressive.

The front sprocket I think is the same as a late model Gas Gas. They have them here:

http://trialstribulations.net/index.php?main_page=product_info&cPath=24_16_75&products_id=442

Sussed this myself now, Ossa been Ossa use a 8mm bolt with a 10mm location shoulder to fasten the rear sprocket on to the hub, so you cant use the standard Ossa bolts with other sprockets as they only have 8mm holes in them also the head on the Ossa bolt is bigger than normal and does not fit in the counterbore on after market sprockets.

I have fitted a Talon 41 rear sprocket using good quality SS dome heads and locknuts with a 10 tooth front sprocket, this gives the equivalent of 3 extra on the rear over standard.

Edited August 1, 201214 yr by taff_d

I saw some Jitsie sprockets advertised for Ossa - would they bolt straight up I wonder??

I've seen them myself but they where mail order they would fit with the std bolts know doubt.

More expensive as well !

Edited August 2, 201214 yr by taff_d

Cambridge Trial Centre had them on ebay, I thought the price was alright but they don't have a shipping option to Australia.