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 sprockets and chains, oh my!

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MadYam




PostSubject: sprockets and chains, oh my!   Thu Jul 12, 2018 10:50 am


I'm in the middle of installing a 14/49 combo with a 112 link chain. Using Sun Star sprockets and a RK chain. I have the Sandman case saver.

Question 1: The front sprocket has a flat side and a side with a little lip. It's not clear which direction the lip should go - engine side or nut side. I'm eyeballing the alignment, but was wondering if others have experience with this to confirm the proper orientation. Right now I have the lip going toward the engine, which pushes it slightly further from the engine than the other orientation.

Question 2: I see a lot of opinions on chain tension with sprocket changes. Some say "just use the factor setting" of 8mm-13mm from the swing arm. Others say "use the factor setting, but adjust for the added diameter." The math of how much the chain moves away from the swingarm, relative to the stock sprockets, appears to be 9mm at the mid-point of the chain. So in theory, if I want the same chain deflection, I'd add 9mm to the 8mm-13mm distance, making it 17mm to 22mm from the swingarm. Before I get this wrong, can anyone confirm or correct my math or the theory on chain tension and deflection?

Thanks much!
MadYam
2015 WR250R
2016 Super Tenere
1987 K75S
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MadYam




PostSubject: Re: sprockets and chains, oh my!   Fri Jul 13, 2018 9:17 pm


OK, so I went with the lip side out, but in truth, either side ended up having the same alignment due to the structure of the sprocket. It lined up along the chain guide identically. I did find that my Sandman case saver will not go back on, unless I want the chain to rub against it. For now, I'll run without it.

For the chain tension, I found a reference to someone with a 14/50 combo having done the swingarm alignment technique. Their result was a total of 1", or 25mm once it was on the side stand. That is pretty close to my estimate of adding 9mm to the 14/49 combo. So I set tension a bit less than an inch, pressing up from the middle of the chain while on the side stand. Did a test run and it all felt pretty good.

I also replaced my tires, adding D606 to the rear (MT21 front). With the taller profile of tire, the increased gear ratio ends up just about where I was with stock. I'd set my SpeedoDRD thing with a GPS, back with the stock tires and gears. On my test ride, I found the speed reading was about 1mph higher than the GPS. Close enough for me to keep it the same. Maybe I'll try the 13 tooth and see how much it screams at speed.

MadYam
2015 WR250R
2016 Super Tenere
1987 K75S
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Hertz

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PostSubject: Re: sprockets and chains, oh my!   Fri Jul 13, 2018 10:17 pm

With different than stock gearing I just followed this procedure:
http://wr250r.com/articles/chain-adjustment-guide
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