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Discussion Starter · #1 ·
Hello all,

Got a 1980 CM400A with stock sprockets. I'm replacing the rear tire and since I'll have it off I'm going to replace the chain and the sprockets. I want to change the gear ratio so that the bike is not so buzzy on the highway. From what I've read in the forums here is that that changing the front to a 17 and keeping the rear the same is a good option. Is this correct? And if this is correct does anyone have any good resources to find said sprockets?

Thanks,
David
 

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Just to give you an idea how much of a change to expect, if you're cruising at 6000rpm with the stock 16/35 sprockets, changing to 17/35 would lower rpm to 5640. Changing to 17/36 would result in 5820 rpm. Either will result in some loss in acceleration and little/no increase in top speed. Others here have gone this route, hopefully some will be along to relate their experiences.
 

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I am using the 17/35 on my CM400T2. I don't notice a huge difference from a dead stop, but I do notice a more pleasant cruising rpm.
 
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Discussion Starter · #4 ·
Sounds like changing to a 17 rather than 16 is the best bet for what I'm wanting, thanks! Would a 17 front sprocket be common to find on the web to purchase, or is there place you all recommend for our old bikes? Also since I plan on getting a new chain anyway, do I have to get a different sized chain, or would stock do?
 

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Stock chain will be fine. I'd suggest JT or Sunstar sprockets, it's the same sprocket as the manual trans bikes.
 

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Discussion Starter · #6 ·
Ordered a 17 front and 35 rear from Sunstar, thanks again! I've never removed sprockets before.. The rear seems simple enough with the four bolts and the front with two.. Any tips advise, anything I'll need in advance to change both of them out?
 
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