Trials Australia Forums

What might be looking like a second (lower) spring in the forks drawing is the damper rod

Going back to my rear hub/sprocket, I wonder If I have a wheel off something other than TY.
(My sprockets line up with a FLAT TY175 rear sprocket fitted, not the dished sprocket).

My wheel hub measures approx 128.5mm from the brakeplate outside flange to the face on the other side of the hub where the sprocket fits, (the face on which the inside of the sprocket bolts to the hub).
Distance between my swing arm 'plates' at the wheel spindle position is 205mm (inside of plates).
That all seem right or what?

Interesting that my box of bits came not a 53 tooth dished sprocket but with a 51 tooth dished rear sprocket fitted, (with the dish facing inwards, -not seen that before). Wonder if it came from a DT or something. Hmmm...

Hi Jools, I don't have a TY250. However if I did and was going to give advice, I can see I'd be asking about the length of your rear hub spacers as asked before.

Also a picture tells 1000 words.

If you can post a photo of your parts on a bench etc, someone (like David TY Lahey) who have had plenty of experience with the TY250 could say the sprocket you have is wrong, the hub is incorrect or the spacers are wrong size/side/etc.

Does your hub look centre? As in the brake hub stay arm is fitting correctly and not forced to one side to fit.

Standing on the outside imagining what it all looks like, I am thinking that your supplied sprocket may be incorrect. I would also ask my own silly questions
1 Are you looking to restore to concours standard?
2 Are you looking to ride it in a trials event or 3, as any and all trials bikes should be?

If you're looking for a concours standard, I can understand the detailed restoration. If you're looking to ride her? I'd fit a sprocket that suits and enjoy years of pleasure.

Just my 2 cents.

Well one mystery is solved. The reason the PO had mounted the dished rear sprocket facing inwards was so the chain would clear his aftermarket shocks which have fat 63mm (2 1/2") diameter springs that would have interfered with the chain/sprocket. (I don't think he ever ran it like this because there's no wear on the sprockets). Hub and frame are all good. I'll need to get shocks for the bike and am looking at NJB, but I need to check if they will clear the chain, i.e the springs need to be more like 2" diameter at most. The shocks I'm looking at ('NJB Classic Expert') are supposed to be mounted USD which could present a clearance problem with the sprocket.

The bike is not intended to be concourse. It'll be pretty nice, but It's a user for sure.
Dunno about you but I've built about 8 bikes out of boxes parts, and I.D.ing all sorts of odd, strange, mysterious combinations of PO concocted parts is all part of the fun, - sometimes frustrating, but very satisfying when fixed.

Next...
Rear shockers. I want to order these soon. I've seen the options: Falcon, Betor, NJB. I feel NJB might be good as previously mentioned, but I'm just a little wary of the clearance of the shocker to the chain/sprocket. Any clues on this? Experiences?
-Jools
On another subject, I'm a little confused that the TYtrial site are selling 44T rear sprockets for the 250TY when 53T are standard? What gives here?

Jools wrote:Next...
Rear shockers. I want to order these soon. I've seen the options: Falcon, Betor, NJB. I feel NJB might be good as previously mentioned, but I'm just a little wary of the clearance of the shocker to the chain/sprocket. Any clues on this? Experiences?
-Jools
On another subject, I'm a little confused that the TYtrial site are selling 44T rear sprockets for the 250TY when 53T are standard? What gives here?

44 big (520) teeth = 53 small (428) teeth
520 chain is bigger pitch than 428
428 is standard pitch
Some people prefer 520 chain

With modern trials shocks mounted spring-at-bottom on TY250 or TY175, you will need to space the shockie out a bit so the spring clears the chain.
Some work either way up. Some only work with spring at bottom.

Ah, didn't think of that 520 / 428 thing explaining the difference in sprocket teeth. Of course.
Thanks for that David.
Yes, rear shock / chain clearance, -I'll need to keep tabs on that before I buy.
I'm a touch wary about spacing the shock out on the lower mount to clear the chain, -those mounts are not THAT sturdy down there are they. Hmmm...
On the other hand if other guys have done it successfully, why not?

Jools ... dished sprockets are available from B & J Racing in the US.

Alastair

Just measured springs on my TLR, Falcons a Flys over 2" & Betors right on the 2; mark