TT250 49 tooth sprocket from CSC
 

A 49 tooth rear sprocket with spacers is now available from CSC for the TT250.

Is this worth getting or would it be better to wait for a 47/48 tooth. I'm unsure how one tooth drop would really improve top speed that much. Any thoughts from experienced riders.

so yer have a 50 on it... going to 49 is just tossing money away...

3 teeth on the rear is = to 1 tooth on the front....or so close it
dosn't matter... so 1 tooth on the rear is like 1/3 of a tooth
on the front....



...

Do you have a 17 on the countershaft?

Joe B wrote that it made a noticeable seat-of-the-pants difference. They're pretty cheap, so I bought one.

I was going to install it today, but even though I am pretty sure where the spacers go and which way the dished face of the sprocket should face, I don't want to guess.

So if anyone knows, please chime in.

Cheers,

Dan K.

OK, I decided to give it a try at least, but now I'm at a dead end for two reasons.

1. I placed the new sprocket and the old sprocket on a flat surface. I placed the four spacers under the new sprocket. I viewed them side-by-side from the edge view and the new sprocket is a little more than a millimeter lower than the old sprocket. I'm thinking that the purpose of the spacers is so the new sprocket runs in line with the plane on which the old sprocket ran (That is to say, in-line with the counter shaft sprocket and chain)

2. The only way that makes sense for the spacers is that they are inserted between the sprocket and the hub and are held in place by the four sprocket mounting bolts. Unfortunately, the inside diameter of the hole in the spacers is less than the diameter of the mounting bolts.

I am officially stumped.

Cheers,

Dan K.

I cannot help you on the spacers, but this video will answer the question on sprockets as he did not get any more top speed, but less vibrations with a 43. Perhaps write him on youtube and see if he needed to do anything for that aftermarket sprocket? He is a member on the FB group, 'China Bikes North America' Also, he does have a swearing attack, LOL, so if anyone is offended, turn the volume way down.

https://www.youtube.com/watch?v=ty9RDzq1SEk

I was concerned about this when I read Joe's blog.

If the spacers are within 1mm, that's fine. I'm running a flat sprocket on Mrs 2LZ TT with a 7mm offset with no odd wear, noises or problems. Let's not forget the countershaft sprocket wobbles quite a bit on the countershaft. Over the entire length of the chain, that should allow the chain to point in a wide variety of directions.

My concern about the spacer setup, if I understood it correctly, was that the stock sprocket is held on by a giant C-clip and with the spacers, I was at a loss to imagine how you'd reuse that c-clip.....or not. I'm sure that huge C-clip is there for a reason. I'm by no means questioning Gerry's expertise, but this setup just brought some questions to mind.

It seems to me that losing only one tooth on the rear sprocket should theoretically not make much difference. I know someone here can do the "ratio math". I'm running a 47 (JT249.47) and it's still a little short legged on the open road....but fine for our local twisties.

Or, I could just simply answer directly and help, here. :)

So, the original sprocket is convex OUT to the hub. For my swap, I did simply flip the stock sprocket flip to face the hub, and bolted the new sprocket to that dish portion. It worked awesome.

Now, for the concerns of the exact in line presence of the chain -- Have you guys fiddled with the front sprocket? That little bastard has a lot of play already. I wouldn't be too concerned over the 1mm difference, especially when you consider how cheap all of these parts are anyway...

In any event, I'll be swapping my 43 with a 45 for experimentation. It's on order claiming it'll be in next week... we'll see if my order for this one gets canceled again like the last vendor. ;)

Dave aka Ghaniba

I should also mention -- the Circlip I left off of mine entirely. It's there to hold the sprocket to the wheel. It's never going to be load bearing -- the 4 bolts do that. Without the bolts, it just spins on the wheel.

As for the spacers being too small for the bolts to go through... now that's some funny nonsense. Someone clearly just guessed, or, only checked one of their bikes before claiming that those washers were the right side "spacer" hehehe

Dave aka Ghan

That Joe B must have the most senstive "seat of the pants" in California if he can tell a 49T from a 50T sprocket....that's like a 2% change to the gear ratio???

JMO, taking apart the rear end and doing a sprocket change to go from 50 to 49 seems kinda silly to me...have fun.

So with the new sprocket your engine RPM at 51 MPH will be the same as your engine RPM was at 50 MPH with the stock sprocket. My "seat of the pants" is not calibrated nearly that well lol.

There's some people over on the TT 250 owners page on Facebook that have dropped down to a 43 using what I believe is a JT sprocket that they are opening up the center a bit and then flipping the stock sprocket and using that as a spacer. They seem to be getting good results with this setup. I'm thinking about trying it myself since my TT is used solely as a commuter and I'd like to have it turn fewer rpm since a good stretch of it is 55 mph. The only thing that I would like to do is machine down the stock sprocket so it doesn't protrude above the new one but that's more of a visual thing rather than a functional one.

With our 47 tooth, it's a really good, all-around gearing for it. It will sustain some higher speeds for a while but for regular commuting, I'd probably go with a 45 or 43. I went too far on Q and actually lost top speed on hills or headwinds due to lack of torque and too tall of gearing. I added a couple teeth and actually increased my top end because it kept it in the powerband.

Regarding hogging out the middle of the JT sprocket, it doesn't take much at all. Basically remove the paint and it will drop on. At least that was my experience.

My "personal jury" is still out on the double stacked sprockets. I'm going to be watching them for a while. To me, that huge c-clip on there is probably there for a reason, though one wouldn't think that the awesome raging power of a CG230 wouldn't require much. ;-)
I can say that I'd rather do the stacked sprocket option as opposed to separate spacers. More overall support. Just a personal opinion, not scientifically studied fact.

I've been running the jt 43 tooth for some time now. was probably the first to try it. posted results with pictures months ago. I first used the stock sprocket flipped as a spacer giving it the dual range setup. but honestly the chain is better aligned with no space and no dish than with the stock sprocket dish. all it takes is a sanding drum to remove the paint from the center hole of the jt sprocket to make it fit.


I generally cruise at 62mph but if I'm in traffic the pocket of air the cars and trucks generate has dragged me up to 70 before.

How many links did you have to cut off the chain for the 43 to work?

I just read on the CSC blog that the circlip is only on there for assembly purposes at the factory and can be left off when swapping sprockets.