RL250 switch to 520 chain

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Takhli44
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Bike: TY 175
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RL250 switch to 520 chain

Postby Takhli44 » Mon Apr 30, 2012 3:26 am

520 chain conversion: Rear sprocket from DS 185, 1978 to 1980 with a spacer will fit.

Front sprockets from PE 250, 1977 to 1981 or RM 250, 1976 to 1981 will fit.
I am using 11/39 ratio that seems to work really well with a light (one finger) pull clutch.


Don't let competition get in the way of having fun.

i-moto
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Bike: Suzuki RL250

Re: RL250 switch to 520 chain

Postby i-moto » Tue Jun 23, 2015 3:31 pm

Hi all,

Just wanted to update this with some extra info for Australian RL250 owners, and address one concern I had with the original post.

Rear Sprocket Spacer:
To switch to a 520 chain, you do indeed need a spacer. Original rear sprockets were dished and are no longer available unless you're very lucky. The spacer is also used with 428 chains / sprockets as aftermarket sprockets are all flat. So before undertaking the conversion, check your bike as it may already have the spacer! If you can't be bothered getting one from overseas, your local machine shop should be able to make one very easily if you can supply them an old sprocket for a template. Otherwise the spacer can be purchased from BJ Racing in the US:
http://www.bjracing.com/rl250ts.html

Rear Sprocket
Firstly, the DS185 is not a model we got in Australia, so this may throw some people.
For Australia the most common models that fit are the venerable old TS185 and the ag version TF185, but also DR200 are relatively common here. The JT Sprocket (part number JTR811) comes in maximum of 48T, and also comes in 46T, 45T and 39T according to below:
http://www.jtsprockets.com/catalogue/sprocket/JTR811

My problem with the original post is that my bike came with 13T Front and 39T rear (very tall!), but even with that combination my bike had evidence of the chain rubbing on the swingarm and slowly wearing grooves into it, probably made worse if the chain isn't tight enough or goes out of adjustment, so I can only imagine that with an 11/39 combination as posted by Takhli44 this problem would only be exacerbated as the chain would pretty much be sitting on the swingarm even when tight. The original rear sprocket was much larger in diameter, and I don't think these bikes were designed to run anything less than 45T for this reason.

Has anyone else had experience with this?

I've since switched to a 45T rear and retained the 13T front which gives me a ratio that I'm really happy with, and seems to have eliminated the chain rubbing on the swingarm. For most people this ratio is probably still too tall, so the 48T rear and 13T or 12T front are shorter geared options.

Front Sprocket
I'm yet to replace mine so can only assume the original post is correct - if anyone can confirm that would be great.
Should be this one, which also fits other common models found in Australia including Yamaha XT250 of all things!!
http://www.jtsprockets.com/catalogue/sprocket/JTF431

Hope some of this helps.
Cheers,



paulo
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Re: RL250 switch to 520 chain

Postby paulo » Wed Jun 24, 2015 7:06 pm

I made up a swingarm protector/chain guard from a nylon chopping block. Heated one end up then formed it to the curve i was after. I tapped a 6mm dome head bolt into the swingarm gusset to hold it in place.
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i-moto
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Joined: Fri Nov 13, 2009 7:59 pm
Bike: Suzuki RL250

Re: RL250 switch to 520 chain

Postby i-moto » Thu Jun 25, 2015 8:27 am

Great idea and well executed, will have to do the same I think.



i-moto
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Bike: Suzuki RL250

Re: RL250 switch to 520 chain

Postby i-moto » Mon Jul 13, 2015 7:52 am

Can confirm that the front sprocket as listed & linked above is correct and fits perfectly (JT Sprockets JTF431).

11T front and 45T rear gives 4.0:1 ratio, which is shorter than factory and works brilliantly. Could even go to a 48T rear.

Setup works well with the addition of Paulo's swingarm guard, which is necessary to stop the chain digging grooves into the swingarm.

Cheers,
Tom



Takhli44
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Re: RL250 switch to 520 chain

Postby Takhli44 » Tue Oct 20, 2015 1:48 am

I like the swing arm guard....I solved the problem with a dab of brazing rod in the critical area


Don't let competition get in the way of having fun.

pop
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Re: RL250 switch to 520 chain

Postby pop » Tue Oct 20, 2015 10:00 am

paulo wrote:I made up a swingarm protector/chain guard from a nylon chopping block. Heated one end up then formed it to the curve i was after. I tapped a 6mm dome head bolt into the swingarm gusset to hold it in place.

How did you heat it up? is boiling water enough to form it?



i-moto
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Posts: 39
Joined: Fri Nov 13, 2009 7:59 pm
Bike: Suzuki RL250

Re: RL250 switch to 520 chain

Postby i-moto » Wed Oct 21, 2015 7:32 am

I used a butane torch to heat it, not sure if boiling water would be enough.

Interestingly, I used the same material to make a block for the chain tensioner - has held up really well so far.

The cutting boards can be had from Kmart - $4 for a pack of 3 from memory.




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