KZ650 CSR/Ltd frame and front fork differences

 

I am thinking about converting my kz into more of a cafe racer. But I think that I have a CSR/LTD or whatever they were designated as, which features the more "chopper" like front end.

My question is whether the difference is only in the triple tree and front forks or it is the actual headstock angle in the frame that is different? Meaning that, could I just buy a front assembly with triple trees and forks to convert it into the "normal" kz650 geometry?

The Ltd and CSR's having "leading axle" forks and less "off-set" in the tree's. If you swop the tree's and forks complete from a non "leading axle" front end this will keep the "trail" at an acceptable level and should steer just fine - The 1000ltd does have an extra 1.5 degree's of rake (I am guessing the 650 will be similar) but if the trail is kept in check then it should ride just fine (you could "jack" the rear or drop the forks through the trees a little to reduce the difference)

Wookie58 wrote:

The Ltd and CSR's having "leading axle" forks and less "off-set" in the tree's. If you swop the tree's and forks complete from a non "leading axle" front end this will keep the "trail" at an acceptable level and should steer just fine - The 1000ltd does have an extra 1.5 degree's of rake (I am guessing the 650 will be similar) but if the trail is kept in check then it should ride just fine (you could "jack" the rear or drop the forks through the trees a little to reduce the difference)
 

Ahh so the "normal" trees actually has off-set in them to bring the tire closer to the engine? Because I looked at mine at it seemed like the forks and the headstock/steering stem follow each other. Of course it would probably be difficult to see the 1,5-2 degree angle offset that I can understand is the difference between them. Hence I was afraid that the angle was in the headstock and frame and not in the trees/forks. But it would just seem like a costly affair to make such a big difference in the frame as opposed to in the trees/forks. 

*Edit reading through your answer again you are perhaps saying that there is a difference in both frame and trees/forks? But new trees/forks should close the gap enough to make the difference negligible?

q-base wrote:

Wookie58 wrote:

The Ltd and CSR's having "leading axle" forks and less "off-set" in the tree's. If you swop the tree's and forks complete from a non "leading axle" front end this will keep the "trail" at an acceptable level and should steer just fine - The 1000ltd does have an extra 1.5 degree's of rake (I am guessing the 650 will be similar) but if the trail is kept in check then it should ride just fine (you could "jack" the rear or drop the forks through the trees a little to reduce the difference)

 

Ahh so the "normal" trees actually has off-set in them to bring the tire closer to the engine? Because I looked at mine at it seemed like the forks and the headstock/steering stem follow each other. Of course it would probably be difficult to see the 1,5-2 degree angle offset that I can understand is the difference between them. Hence I was afraid that the angle was in the headstock and frame and not in the trees/forks. But it would just seem like a costly affair to make such a big difference in the frame as opposed to in the trees/forks. 

*Edit reading through your answer again you are perhaps saying that there is a difference in both frame and trees/forks? But new trees/forks should close the gap enough to make the difference negligible?

The trees won't change the angle, the extra off-set pushes the forks forward from the stem which reduces "trail" and also if you are planning on "ace bars" or "clip-ons" it will give more clearance between the bars and the tank on full lock - dropping the forks through the trees maybe 10mm will reduce the difference of the headstock angle

Wookie58 wrote:

The trees won't change the angle, the extra off-set pushes the forks forward from the stem which reduces "trail" and also if you are planning on "ace bars" or "clip-ons" it will give more clearance between the bars and the tank on full lock - dropping the forks through the trees maybe 10mm will reduce the difference of the headstock angle

Ahh, yes okay. The off-set will primarily aid in clearance around the tank. So the "normal" forks/trees have more off-set but then are "non leading-axle" design. But do you know if the forks are actually shorter? Because currently I have the forks lowered as much as possible with the tops touching the handlebars. So if the "normal" forks are not shorter then I would be worried about whether there is anything to gain at all with "normal" forks/trees apart from the clearance around the tank?

Not sure on the 650 - the 1000 has a 30mm difference. I suspect they are shorter as the CSR/Ltd has a different part number for the tubes (maybe one of the 650 guys can measure theirs for you) You could also use an 18" wheel from a GPZ550 etc to lower the front

Wookie58 wrote:

Not sure on the 650 - the 1000 has a 30mm difference. I suspect they are shorter as the CSR/Ltd has a different part number for the tubes (maybe one of the 650 guys can measure theirs for you) You could also use an 18" wheel from a GPZ550 etc to lower the front
 

Okay, no worries you have already helped a ton! It would just be interesting to know if I would actually gain anything from buying trees and forks compared with the ones I have now that is lowered in the trees. 

That is also a good idea. Is the wheel a direct replacement?

I believe so (might just need different spacers knocking up)

I do not know if this will be of help or not. But I have some data from 650 FSMs note not all models. From what I have it appears there were basically 3 different set ups for the 650s.Some have a trail of 108mm, or 113mm or 115mm.

        steering angle    castor        trail
B1        39.5degrees    63 degree    108mm
B2A        39.5        63        108
D1A        39.5        62.5        113
B3        39.5        63        108
C3        39.5        63        108
D2        39.5        62.5        113
D4                27.5        113
F2                27        108
H1                29        115
E1        39.5        27.5        113
F1        39.5        27        108
F3                27        108
H2                29        115

Those steering angles seem excessive? On the “J” models the Ltd is 29 and the J is 27.5 !!

That frame looks to be a CSR not LTD, model year is most likely 1981-82. Only thing is you have a earlier engine installed as the CSR engine did not have a kick start lever. Most likely the engine 1980 or earlier.

If you compare that frame to a B/C model frame you will note the neck is jacked up. Same with the rear of the frame, they are shorter because they don't have the mounts for the plastic tail piece.

You can find more info here :

www.jarlef.no/Kawasaki/Series/Z/650/z650sr.htm

You can check frame and engine numbers on that web site for all 650 models.

There is nothing wrong with those leading axle forks, '81 GPZ550 used the same forks. You can lower the ride height by using a internal limit block. I have those same forks and lowered them by about 1". The SR/CSR/LTD models did use slightly longer fork tubes than B/C models.
 

Thanks a lot Injected! That page is a treasure trove.

But are you saying that the neck is both angled differently and also moved higher? It sounds a bit like I should hunt for another frame if I want to build a cafe racer type bike and want to benefit from the original kz650 handling characteristics.