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Lowering chain guide
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Hi

I'm changing the chain and sprockets on my Raid and have read (here, for example, http://ttr250.activeboard.com/t48120247/sprocket-question/) that the chain guide needs lowering.  I've looked in the service manual which doesn't help because it assumes that you're replacing like with like - I'm replacing 428/18-52 with 520/14-52 - and on the stickies here but there's no answer to the question - what's the criterion for how far to lower the chain guide?

Help?

Thanks

Pete

 



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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.



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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



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

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



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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 wink

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

Brian


 OK Brian, will do.  Watch this space.

 

Peter



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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



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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



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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



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

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.

IMG_3796_small.JPG

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

Jarrah

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



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TTRfan wrote:

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


 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



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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



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

Peter



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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



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