ty 250 b gearing

[kevste]

am writing this again as i am not sure whether last message worked.
i have a ty 250 b. it came with 520 sprocket chanin combo, adn had a 40 t rear and 12t front. i have changed to a 428 chain and a 13 t front and 52 rear as advised. however, this combo still is too high geared. it seems all i can do now is go smaller on teh front, but by how many 1t, 2t or 3t? i guess this will cause chain clatter on the swing arm, has anybody got any ideas for optimal gearing ? and where to buy someting like neoprine to make a chain 'guide' for the swing arm.
cheers

[Stu]

Kevste,
I have a TY250a and I use it for anything from a trailbike to a trialsbike. I have a 13t front and a 52t rear sprocket. I have a 12t for the tight stuff. You can still get them from Yamaha NOS.
An old neoprene chopping block should do, just mark the chain guide on it and cut it out.

[kevste]

cheers Stu for quich reply, i will be onto it next week. good to know about the 12 t option i was going to go down to an 11t, but that could be slug pace.

[gordonmichaellee]

Changing a front cog by 1 tooth is worth about 4 teeth on the back.

Are you sure you mean neoprene? I thought that was the stuff wetsuits are made from.

My advise on the gearing issue is to only change 1 tooth on the front at a time unless it is an enourmous amount away from where yo want it.

Also consider going bigger on the back if you think it( going smaller on the front) will start other issues with the swing arm.

Cheers Gordo

[Stu]

Gordo, you are right! Neoprene is for wet suits. Dunno whats is called, it's the white plastic cutting boards are made from.

[gordonmichaellee]

Yes Stu I thought so.

I have made a chain slider out of thick builders bucket, but I do think the chopping board stuff might be better as it will have less friction. On the drawback side I think you might find that it will leave small strands of plastic on the chain.

Chears Gordo

[Gary B]

The stuff you need for chain blocks is called "Ralloy"
It's like the white plastic that bread boards are made from.
Try to get off cuts from an industrial plumber.
What we used to do years ago was get skate board wheel & carve a big groove in the centre (just wider than your chain). Then use the standard chain tensioner as a pivot point & have the skate board wheel work as a tensioner / roller instead of a block.