kz400 with a gxsr 600 forks and rn250 swing arm

[flaco]

i need serious opinions on how this look . i know the tire need to go .and the seat to ,the swing arm opinions ?

 

[xb33bsa]

what is the swingarm,shock and linkage from ?
you want opinions on how it looks how about if it will work ?

 

[flaco]

from a zuzuky rm250 enduro .

 

[focusinprogress]

for starters, the rear is sitting higher than the front, which leads me to believe the GSXR forks are shorter.... sitting in your picture it already looks like where the wheel/tire sit not is about the least amount of travel I could consider comfortable to have...lowering the rear to get the stance back square would mean having nearly no rear travel available before contacting the subframe/seat.

as for if it would actually work, if you have the rm250 bike to measure, you will want to mount the shock in the same position on the KZ as the RM, matching angle and placement so that the linkage works as it was calculated for and the shock valving and spring rate do what they are supposed to. Weight would also be a concern, comparing an RM250 to a stripped down KZ might mean increasing the spring rate and/or re-valving the shock.

Also, the length of the front forks and the offset in the triple trees will affect your trail measurement. A lot of the old bikes I've done front end swaps on I've had to make custom triple trees to get the trail corrected as the GSXR trees only have about 25mm +/- of offset when I've often needed 48-54mm of offset for trail to remain at stock.

 

[warpt_99]

the swingarm looks a little long for the frame. it's going to take some serious ingenuity to get this work properly and safely.

 

[xb33bsa]

it wont work, not even close, the rm has near 12" of wheel travel
and the linkage and shock is designed for that,you would need a complete re-design to use that swinger and if you haven't even recognized that yet you are in WAY over your head
you would need to find triples with more offset as well for the forks

 

[focusinprogress]

if you're looking to convert to mono-shock rear, I've had really good luck with kawasaki ex250 (ninja 250) rear ends. they aren't nearly as long as larger sport bike and dirtbike/dual-sport ones and the travel of the shock is very similar to a lot of these old bikes. Did one on a cb360 recently and on the softest settings it's a pretty nice improvement without being overly stiff.

 

[warpt_99]

if you're looking to convert to mono-shock rear, I've had really good luck with kawasaki ex250 (ninja 250) rear ends. they aren't nearly as long as larger sport bike and dirtbike/dual-sport ones and the travel of the shock is very similar to a lot of these old bikes. Did one on a cb360 recently and on the softest settings it's a pretty nice improvement without being overly stiff.

Do you have any pictures? Really interested to see how you got this to work?

 

[focusinprogress]

Do you have any pictures? Really interested to see how you got this to work?

the cb360 frame is as if it were designed for an ex250 mono-shock....made 4 tabs and they were able to be welded to stock frame cross-members.

Lower mount to bottom cross-tube just behind/underneath engine:

top shock mount tabs welded to cross-member just behind the carbs:

mounts were 1/8" thick steel plate...we later boxed in the mounts for strength and then added frame gussets below the gas tank mount and the corners of the cross-tubes into the vertical frame tubes.

 

[warpt_99]

I'll give it to you, looks like you got it working properly. Does the shock affect ground clearance or it pushed so far back the rear wheel makes the clearance work?

 

[focusinprogress]

as suspension loads/travels the linkage at the bottom moves upward away from pavement. it's only about .75" lower than the exhaust once that is mounted, and it's dead-center of the bike, so it won't come into play cornering, would only come into play if you ran over a foreign obstacle such as a large tree branch in the road or something....at which point the clearance of the linkage is the least of worries

 

[warpt_99]

that would be the least of your worries, haha.

 

[warpt_99]

Very impressed though with your assembly

 

[xb33bsa]

the cb360 frame is as if it were designed for an ex250 mono-shock....made 4 tabs and they were able to be welded to stock frame cross-members.

Lower mount to bottom cross-tube just behind/underneath engine:

top shock mount tabs welded to cross-member just behind the carbs:

mounts were 1/8" thick steel plate...we later boxed in the mounts for strength and then added frame gussets below the gas tank mount and the corners of the cross-tubes into the vertical frame tubes.

that fits nice but you do need a lot more bracing on the top and bottom shock mounts
on the top mount some tubes running from the bolt straight up to the backbone would be the idea something to eliminate the twisting moment on the rear frame cross tube
the bottom mount pretty simple just double up on the strength of the bottom cross tube
the way it is now it will fail eventually