Widening the KZ frame...

oh and just realised this is in the wrong section. Can a moderator please move it to the chassis section? thanks

Hey guys so I need some input please.

I have to widen my frame at the pivot point to accept a wider swingarm. It's about 45mm wider total. So I need 22.5mm (or about 7/8") either side if I keep things central.

The frame doesn't have enough metal to remove that much without weakening the pivot points. It's a shaft drive so the pivot points are also threaded to hold the pivot pin/bolts that hold the swingarm. Here are some pics so you can see what I'm referring to. The whole issue is complicated by the fact that 3 tubes join at this point of the frame and there is like a folded gusset over the inside and outside of the joint. What do you think would be the best way to widen the frame?



a) Cut the cross supports and stretch the frame at the pivot point, then weld in new cross supports and bracing? This may misalign the threaded pivot points from being perfectly parrallel.
b) Add material to the outside of the pivot points which will allow me to remove the required amount from the inside of the pivot point Downside is the added material won't be directly under the tubular sections that join at this location, but rather "next to them"
c) Cut out the entire pivot point and insert completely new section that can be laser cut from thick steel plating, with locating points that go into the tubular steel before welding it together. Then thread the new steel plating for the pivot bolts. (let me know if I need to draw something to explain this better)

Illustration of approach no "B" described

Rough illustration of the third option mentioned. The steel section can be cut from steel and then the sections that will protrude into the frame will have to bent slightly as the joint is kind of concave at that point. They then get inserted into the frame and welded together.

D) Narrow the swing arm.

C looks like the best choice of the others to me.

D) Narrow the swing arm.

Seems like tail wagging the dog here. Surely easier ways around it?

I know for the GPz z1000 J R etc chain drives there are arms that will accommodate fat tyres with basic machining and twin shock mounts fitted, IIIRC FZR or GSXR 600 ? ZRX 1100 are also quite a popular fit.

The bike is shaft driven guys. Can't narrow the swingarm that much because:

1) The driveshaft location needs to stay relatively put in the original position to connect to the engine.
2) Narrowing it only on one side will mean the wheel is completely off centre,

E) convert to chain

Splitting the cases (if neccessary) and swapping to chain drive components seems a lot more feasible.

can't see the point of a shaft drive on a special. If you are doing 1500 miles a week as a dispatch courier maybe.

Tyrell Corp wrote: E) convert to chain

Splitting the cases (if neccessary) and swapping to chain drive components seems a lot more feasible.

can't see the point of a shaft drive on a special. If you are doing 1500 miles a week as a dispatch courier maybe.

Chain conversion would be the easy way yes, but I guess I want it different. Also can't be bothered with chain maintenance on this bike and the mess it brings.

So let's forget the chain conversion and focus on a solution to the frame problem please

E. Buy another bike.

Trying to widen the frame is a mistake since it may lead to an unsafe / unstable bike or an abandoned project. Below is a picture of the final version of a KZ1000 which the owner decided to widen the frame so he could install a different swing arm. Sad, but this bike that he got for free ended up being parts for sale. Ed

Fit the Kaw engine into the other frame.