Radically High Gear Ratio on My KZ650 CSR

You can convert the 650 pushrod clutch to the 750 rack and pinion version (and vice versa), one of the guys on my site has done it on his turbo.

My turbo runs 18/36 for top speed events, 21mph per 1000rpm in top gear :laugh:

Hi Bill,
The vin plate says '83 KZ 650 CSR, but the VM24 carbs are definitely from an '81. (They're the tall ones like the VM29's). There is a bolted-on shroud in front of the front sprocket that I had to remove. The aluminum casing just took a little filing. The shifter shaft is clear, but gets a little chain lube slung on it without the shroud. I'll try to get pix on Monday and post them. I have the 630 chain also.

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Hey Steell!
Thanks for the info on the 440. Just checkin'. Gotta ask, ya know!

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FYI,
I just rebuilt my carbs and went from 97.5 to 105.0 on the main jet and from 15 to 17.5 on the pilot jet. (Added a 4-in-1 header and opened up the bottom of the air box for my K&N filter). Once I get the bike running again, I'll let you know how it goes.

Post edited by: Spot, at: 2007/10/14 02:15

Spot:
I never bolted the new 16 tooth front sprocket on the bike, but by holding it on centerline with the shaft, the tips of the teeth came within less than 1/8" of the clutch push rod. The chain sticks out at least 3/16" beyond the tooth tips, so on my bike I believe the chain would interfere with the clutch push rod by 1/16". Any collision of parts would be disasterous, in my book.

I am including a photo of the original 13 tooth sprocket in place, with the chain guard and clutch pushrod visible. I believe a 14 tooth sprocket would bolt on without modification. A 15 tooth might fit by modifying or removing the guard. But I just could not see how a 16 tooth would fit. I wish it would. If I wear out my present sprockets then I might try it again.

Sorry, I can't get the photo to load.

Post edited by: WABBMW, at: 2007/10/14 21:45

KZGUY:

Your 13/33 sprockets with 16" wheels will be lower in overall ratio by about 4.3%, as compared to the 18" wheels and 17/42 sprockets. In other words, for a given road speed, the RPM will run higher. I made some assumptions about tire sizes.

42/17 = 2.47 110/90-18 = 25.51" diameter
33/13 = 2.54 130/90-16 = 25.16" diameter

In order to exactly match the earlier ratio, the rear 33 tooth sprocket would have to be reduced to 31.7 teeth. Since we must work with whole numbers, a 32 tooth would move you closest to the desired figure. But this is a small difference, and to me it wouldn't be worth changing the sprocket. At 60 MPH you would be turning less than 200 RPM higher.

Post edited by: WABBMW, at: 2007/10/15 14:30

Bill,
I've put over 1,200 miles on it without problems with the shift shaft. I did have to remove the chain guide, though. It's basically an extension of the aluminum side case that acts more as a dirt shield than anything. I took a picture, but the image limit is 250k here. I couldn't find anything I could use to shrink the picture that far. Sorry. Best I could get was 864k. If still you want to see it, my email address is bavants@email.com.

Bruce

Post edited by: Spot, at: 2007/10/18 01:52

steell wrote:

apeman wrote:

ALSO: Someone on this board tried putting the SIX SPEED transmission internals from a KZ550 into a KZ650 or KZ750. This would be nice, if it really works. I don't remember how it all turned out. If I get a chance before the weekend is out, I will search for the threads and post a link.<br><br>Post edited by: apeman, at: 2007/10/05 14:25

The six speed will fit in the 750's (I know for a fact), and should work in the 650's that do not have a kickstart. It's a fairly easy conversion (have to split the cases), but you may have to shim the ends of one or more of the transmission shafts.

Oh great, now there are going to be more people looking for a cheap 550 trans, so I may never find another one

It only gives you just a little bit more on top and bottom, mostly it gives you closer gear ratios, which comes in handy for those with aggressive cams and narrow powerbands.

I'm not sure where you live, but I saw a posting of a 1978 KZ550 for $700 at norfolk.craigslist.org. The guy lives in Poquoson, Virginia.

WABBMW wrote:

Spot:
I never bolted the new 16 tooth front sprocket on the bike, but by holding it on centerline with the shaft, the tips of the teeth came within less than 1/8" of the clutch push rod. The chain sticks out at least 3/16" beyond the tooth tips, so on my bike I believe the chain would interfere with the clutch push rod by 1/16". Any collision of parts would be disasterous, in my book.

I am including a photo of the original 13 tooth sprocket in place, with the chain guard and clutch pushrod visible. I believe a 14 tooth sprocket would bolt on without modification. A 15 tooth might fit by modifying or removing the guard. But I just could not see how a 16 tooth would fit. I wish it would. If I wear out my present sprockets then I might try it again.

Sorry, I can't get the photo to load.<br><br>Post edited by: WABBMW, at: 2007/10/14 21:45

Bill, you're right!! It didn't make any noticeable noise, but 16 tooth sprocket lathed my clutch pushrod by .012 in, if I'm reading my Vernier Caliper correctly. I've put more than 1,200 miles on it since I changed the sprockets. No problems with shifting noted.

According to the link posted by CoreyClough earlier in this thread( www.cunnington1.freeserve.co.uk/gearing_v12.xls ), you need 14/32.

KZGUY wrote:

Hi!, just found out that the rear rim on my recently aquired 79' KZ650 is a 16"!! and current gearing is 13-33. wish to have the same ratio as my other 650 w/18rear with gearing at 17-42. Please help!:ohmy:

Sorry!! Forgot to add quote. See previous post for answer.

OH. MY. GOD. Just put on my 26 tooth from Rebel Gears and my '81 CSR 6-fiddy is everything I dreamed it of being.

I calculated that my starts in first with the 26 tooth rear would be like starting in second with my 33 tooth rear. But starting off really isn't bad, the bike pulls longer and the revs aren't ridiculously high at highway speeds. Unfortunately my tach doesn't work so I can only tell by me ears lads.

The Vance & Hines 4-1 sounds wicked now with the bike winding out longer.

It's like the Kawi has another gear. I love it.

Old news, I dropped my 750 gearing from 2.4:1 (38/16)down to 2:1 (32/16) way back in 1980 because I got sick of the engine screaming 5K @ 70 mph. It dropped to 4200 @ 70 and ran it like that for about 25 years.

bountyhunter wrote:

Old news, I dropped my 750 gearing from 2.4:1 (38/16)down to 2:1 (32/16) way back in 1980 because I got sick of the engine screaming 5K @ 70 mph. It dropped to 4200 @ 70 and ran it like that for about 25 years.

I was kinda thanking WABBMW for his experiment with the 26 tooth rear and describing how I felt about it. It's probably the oldest trick in the book for you "experienced" fellows :woohoo: ... :blush:

But yea I have a feeling I will never go back to my 33 tooth.