KZ650 sprocket clearance

Hi folks. Have a 81 650 CSR. Stock 630 chain with 13/33 sprockets. Now spins about 5K at 60 mph. Has annoying buzz (vibration) between my legs at 55-65 mph. I'm a guy and not into it. Desire to get rid of the buzz at 60 mph and increase the mpgs. Would like to get gear ratio from 2.54 down to about 2.20-2.30 max. Would like to change to 15/33 which would drop the rpms about 600+ at 60 mph and still be plenty torquy for my needs. 15T 630 sprockets are available for front.

I pulled the case cover yesterday and there is only about about 3/16th inch between current 13T sprocket teeth/chain and the chain/engine guard. Z1 Enterprises indicates 15T sprocket is compatible with my CSR H1 but I don't see how even a 14T would fit (more teeth = bigger circumference = bigger diameter.) 650 H1 engine is same as D4 and F2 so I imagine they have the same chain/engine guard clearance problem even with 530 chains.

Has anyone put a larger sprocket on any of these?

It would be logically easier to just go to smaller rear sprocket and not have the clearance issues. Only problem is smaller rear sprocket available is only 1T smaller and not enough for change. I even checked ratios for 530 chain conversion.

I had the same problem. When I went to replace my sprockets and chain, I went with a 15-33 because that's what the bike shop recommended. The 15 tooth front went on, but there was no room for the chain to go on, the sprocket was touching the chain guard! The 15 tooth is definitely NOT compatible. I had to go back to the 13 tooth and stock gearing with a frown...So know I don't know what to do because I can't find a rear sprocket smaller than 32 teeth...I feel your pain.

I haven't looked, but it seems to me that you should be able to remove that chain guard that's in front of the sprocket and get the needed clearance.

I'm not sure if the clutch push rod will clear a 15 tooth sprocket though.

Lot's more sprocket choices in 530 chain size, so you could convert to 530, or you could order a new rear sprocket with as many teeth as you want from Sprocket Specialist.

Computer Guy:

Check out my post entitled "Radically High Gearing on My 82 KZ650 CSR. I tried the same thing on the front sprocket and found that even if you removed the chain guard (which I wouldn't recommend), that the 630 chain will hit the clutch push rod. A 14 tooth sprocket might work, but wouldn't make much difference. I know that a 16 tooth will not work, and I doubt a 15 tooth would work.

So I bought a custom 26 tooth rear sprocket from Rebel Gears. I am still using a 13 tooth front sprocket, giving a 2.00 ratio. I find it to be very pleasant and very good gas mileage.

Will be glad to answer any questions.

I have an 81 650 csr, and changed the sprockets to 16/33, with a 630 chain. I was 1,000 miles from home and had eaten the old chain and sprockets (never go on a road trip 5 days after buying a used bike unless you took a couple of days off prior to, for a thorough inspection).

I had to remove the chain guard, and found out later (with a little coaching from WABBMW) that the chain had lathed two 12/1000's grooves in the aluminum clutch push rod as it operated (if I'm reading the vernier caliper right). I haven't had any problems with it, but wanted you to be aware of it.

Unless you're gonna hammer the bike, smokin' the local competition, a 530 chain and sprockets should work.

If you still want to try the 630, I think WABBMW has a 16T front sprocket you might be interested in.