A forum for owners of Yamaha TTR250 trail and enduro bikes!

Harleyquin · Member

Lowering chain guide

Fladdem · Senior Member

Are you saying your gearing is already 18/52 but with a 428 chain? If so, I shan't imagine that the chain guide would need modifying if it already has a 52 tooth on the back. Correct me if I'm wrong but I read it that that is your current gearing.

TTRfan · Super Guru

I think Peter is replacing the standard Raid chain and sprockets which are 428/18-57 with a 134 link chain.

In which case I would have thought there would already be plenty of clearance for the new 520 set up.

I recommend you fit the new chain and sprockets Peter and see if there really is an issue wink

Hope to get feedback so that I can update the FAQ.

Brian

TT-R250M · Super Guru

Nice work Brian. I was not aware that the Raid's used such large sprockets.

So the Raid's fit an 18 tooth front sprocket and if so does that make a 18 tooth possible to fit to a blue model, or does that only apply to the Raid's running 420?

Cheers,

Jarrah

Harleyquin · Member

TTRfan wrote:
I think Peter is replacing the standard Raid chain and sprockets which are 428/18-57 with a 134 link chain.
In which case I would have thought there would already be plenty of clearance for the new 520 set up.
I recommend you fit the new chain and sprockets Peter and see if there really is an issue
Hope to get feedback so that I can update the FAQ.
Brian

OK Brian, will do. Watch this space.

Peter

TTRfan · Super Guru

An afterthought - the 428 teeth are smaller than the 520 teeth so more can be cut into the same size sprocket so it will be interesting for you to compare the diameter of your Raid rear sprocket with your new one. They may not be that different despite the difference in the number of teeth!

Brian

Harleyquin · Member

TTRfan wrote:
An afterthought - the 428 teeth are smaller than the 520 teeth so more can be cut into the same size sprocket so it will be interesting for you to compare the diameter of your Raid rear sprocket with your new one. They may not be that different despite the difference in the number of teeth!
Brian

Not quite. The diameter of the 428/57 is about 235mm and that of the 520/52 is more - about 265mm though it's difficult to be exact 'cos it's now on the bike.

Peter

TTRfan · Super Guru

Crikey - who would have thought eh confuse

That's quite an increase for 5 teeth less doh

What's the chain guide looking like?

Brian

TT-R250M · Super Guru

Geeze, I shouldn't have deleted my info for the blue/OE models, it may have helped.

Anyway, it went something like this-

If fitting over a 49 rear sprocket you will need to elongate the bolt holes. To do this use a round file (or an electric drill to bore it). As long as you have a bit of materiel to hold it on with you should be fine.

However, the best solution would be to make a bracket up, see HERE.

Jarrah

Ps. thanks Steve for the use of the picture. wink

Harleyquin · Member

TTRfan wrote:
Crikey - who would have thought eh
That's quite an increase for 5 teeth less
What's the chain guide looking like?
Brian

The chain guide looks exactly like the one in Jarrah's photo (thanks, Jarrah, for the info). I'm still not clear, though, how it ought to be set up. I've read somewhere that its function is to protect the chain from derailing because of crud/branches. If that's the case then, presumably, the chain should run freely though it and only come into contact through chain-slap? I'll need to figure this out in order to make the bracket that Jarrah recommends.

Thanks everyone for your comments.

Peter

TTRfan · Super Guru

There is always some slack in the chain and it will run over the orange "slider" at the inside bottom of the guide. You will see the wear marks from the chain side plates on it.

As long as the angle the chain exits the guide onto the sprocket isn't too acute then you should be fine.

Just filing the slots in the aluminium cover might be enough.

Brian

Harleyquin · Member

Thanks Brian. Will post again when everything's put back together again.

Peter

TT-R250M · Super Guru

It might be worth noting that BMSteve fitted a 52 rear sprocket and has already gone through the work of measuring (refer to linky thingymebob above). I have not heard any bad report back from him.

Jarrah