How did you grind the frame for swingarm?

Ok How did you guys who fit a swingarm widen the frame for a zx swingarm. I'm under the impression it has to be machined level and flat so that the pivot is evenly pinched. So does anyone have ideas on how to get this surface even and flat? Or do I have to take it to a shop so they can do the machining. If I grind it it wont be flat enough OR will it??


Post edited by: Snakebyte, at: 2006/02/19 11:59

I narrowed the swingarm, didn't touch the frame. I meaured off how much needed to be taken off on each side, and drew a line all around in pencil, then I used a chop saw to cut it off flat. I just took my time and went real slow, this might not be the best way, but its what my budget allows, and I think it will be just fine. You can't even tell that it was done with the dust seals back on. Oh, I also had to trim the sleve (that aluminum thing with steel ends, if I named it wrong) that goes inside the arm, again with the chop saw. Good luck
Scott

I just did this tonight for a KZ1000 swingarm into a KZ650 frame - see my other post tonight under that thread. I trimmed the swingarm instead of the frame, as the bushings in the frame were too short to work with. The grinding down of the swingarm went very well and came out great using the aluminum tape to mark an accurate grind-to line and finishing and squaring with a flat file

I agree with these guys. I put a FZR600 swingarm on my 1000. I narrowed the swingarm, not the frame. You just never know when you might want to put the original back on. Plus it is much easier to do the swingarm because you can take it off and put it in your lap and get a good look while you are cutting.

Don't widen the frame. Make your modifications to the swingarm only. Find a machine shop and bring your stock one for them to take accurate measurements. On my other bikes i did this on a bridgeport to insure that the hole is perfectly aligned, otherwise your bearings will suffer because of misalingment. Not to mention alignment of the wheels will be difficult. I am not knocking the hacksaw method just pointing to the fact as a warning.

im doing the same thing. approx how much do u have to take off the swing arm to make it fit.

galaxian wrote:

Don't widen the frame. Make your modifications to the swingarm only. Find a machine shop and bring your stock one for them to take accurate measurements. On my other bikes i did this on a bridgeport to insure that the hole is perfectly aligned, otherwise your bearings will suffer because of misalingment. Not to mention alignment of the wheels will be difficult. I am not knocking the hacksaw method just pointing to the fact as a warning.

Grinding the frame won't cause misalignment for the pivot bolt. As long as the bolt is still going through two holes that are the right size is doesn't matter how flush that is.

If it's not ground enough the arm won't fit. If it's overdone the arm will have left to right play.

If you want to grind it you can do so with a dremel. Just take a little off at a time from each side, mock up, grind some more, mock up, etc. until it fits.

Unless you plan on going back to stock as someone mentioned. My bikes a gonner though if I ever were to want to make it stock again. lol

Post edited by: twowheeledterror, at: 2006/02/21 14:53

I'm going to try grinding the frame I have no need to go back to stock. Besides I'm thinking it will be more stable with the swingarm as wide as posible.
I looked om the inside of my frame and it looks like I can grind a 3/8 of an inch on each side before hitting the frame. The only problem will be getting the swngarm pedistols flat. Like TWT said I'll have to grind a little at a time.

To the guys who decided to grind the frame I ask why?
Does the swingarm not have enough meat to machine off? I guess i am confused why you would choose the option that is harder? Also the frame just doesn't have a hole in it, rather a steel tube that was inserted and welded. It is there for ridigitity. By grinding away at the tube you are creating a more flexiable area. Yes you can grind it but again the kz frame needs all the stiffness it can find. If you needed to remove a 1/16 or even 1/6 ok maybe i can see that as a quick fix but 3/8 from each side???!!! what is going to hold the swingarm bolt after you are done??? Seems an awful lot of material to be removed.

TWT- Actually to clear up my previous answer, yes you are right gringing wont change the geomtry but by weakening the swigarm pivot it may flex it more therefore changing the angle in a kinetic way and not in a static one.

Can you post the thickness of the piece before you grind it? I looked at my 650 frame and only about 1/4 inch portrudes inward.

Post edited by: galaxian, at: 2006/02/22 15:33

galaxian wrote:

To the guys who decided to grind the frame I ask why?
Does the swingarm not have enough meat to machine off? I guess i am confused why you would choose the option that is harder? Also the frame just doesn't have a hole in it, rather a steel tube that was inserted and welded. It is there for ridigitity. By grinding away at the tube you are creating a more flexiable area. Yes you can grind it but again the kz frame needs all the stiffness it can find. If you needed to remove a 1/16 or even 1/6 ok maybe i can see that as a quick fix but 3/8 from each side???!!! what is going to hold the swingarm bolt after you are done??? Seems an awful lot of material to be removed.

TWT- Actually to clear up my previous answer, yes you are right gringing wont change the geomtry but by weakening the swigarm pivot it may flex it more therefore changing the angle in a kinetic way and not in a static one.

Can you post the thickness of the piece before you grind it? I looked at my 650 frame and only about 1/4 inch portrudes inward.<br><br>Post edited by: galaxian, at: 2006/02/22 15:33

I didn't recommend taking all the space away from the frame. I'd shave down the ends of the sleeve in the arm a little since they protrude, and then some on the frame as well.

The swingarm doesn't really get flex in the way you are thinking in terms of the frame spreading apart and going together there much... especially if you are running a mono and have a cross brace above and below that point. :thumbup: In terms of stiffness a support added above to hold the upper shock mount more than compensates for the ground material. But you don't want to grind it until that area is recessed obviously. lol

As for it being harder, I disagree. It's easier to shave a hair off the frame where you can have some room for error in terms of geometry than it is to chop the arm and get it right. Imagine if the arm were not paralell on each side. Then it WOULD effect handling.

Post edited by: twowheeledterror, at: 2006/02/22 16:21

If you cut the arm crooked it wont matter. Just imagine that the shaft is still in there in a perfect horizontal plane it wont matter if the sides of the swingar shaft are crokked or not.

galaxian wrote:

If you cut the arm crooked it wont matter. Just imagine that the shaft is still in there in a perfect horizontal plane it wont matter if the sides of the swingar shaft are crokked or not.

It most definitely will!

Why? Because you are counting on the full end of the cylinder for torsional strength. If it's way off kilter you may have contact with just one small arc of each end, which is significantly more weak... and could cause a crease in the arm at the pivot.

Picture a rolled up tube of paper.

If you put your finger on one side of one end and push it's easy to cave that end it.

Now put that entire end in your palm and push... it's a lot more rigid. Same concept.

The frame on the other hand it much more thick and much more dense as far as the metal goes, so you have more room for error.