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Discussion Starter · #1 ·
Decided I dont have nearly enough bikes.........And wanted a fighter.
Was going to build up the VF500 I've got sitting in the yard, but then I pointed out to my brother that I've been storing his Kawi for much too long at my shop.

Quick deal, both of us are happy, and I've got a runner with a clean title......

Plans are.........No idea. Never built a fighter. So I'm just gonna run with what I think looks good, on a budget, and make it fast and light as possible.

Before I brought it home...........





Me and the boy started gutting parts until it got dark, and then I mocked up some cardboard and came back in to the computer to do some planning.......
No bitch pad, and I'm thinking a 4-2-1 tucked under the tail........See what I can come up with. Breaking out the scale tomorrow to see what we can shave.

 

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Discussion Starter · #3 ·
Can anyone tell me how fat a tire I can put on the back without swapping swingarms? The purists forums swear that anything bigger than a 130 will ruin it. I see sites that say it came stock with a 150, but mines got a 130, and I'm certain I could stuff a 170 in there easily. That 130 just doesnt seem like enough tire. If I had a few sitting around I'd just fit some up, but I dont in that size.
 

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Normally one size larger than a stock tire is fine for a standard rim. If you want wider then a rim swap at least should be considered.

I don't know much about the 900 but 4.5" rims will swap without too much trouble into a Gpz750. Allows the 750 guys to run 160mm tires.

Later, Doug
 

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Discussion Starter · #6 ·
This is a little differant for me for more than one reason. First build where I'm going to be extremely consious of weight.
So we broke out the scale, trying to save every pound possible.
Stock weight is listed around 501 lbs.
Honestly I think thats a little light.

As pictured it weighed 225 lbs on the front, 210 on the rear.
Tank weighs 9 lbs
Rear subframe and seat are 21 lbs
Airbox weigh 5 lbs

Crunching numbers the new subframe and seat should be about 8lbs. Saves 13lbs there, another 4 lbs going to pods, I was hoping with all the crap on them factory I could get down to 400lbs, but reaslistically it looks like 470? ish. Need to put this thing on more of a diet for sure.





Another differance is normally I would just fit one piece at a time as I pull them off the CNC table, but since I'm doing this at home, I'm going to try to get everything mocked up in CAD board before I cut anything. Need to pinch and slim a few things, but should be cutting it in a day or two.



 

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If your trying to depork her a bit, look into swing arm swaps, wheel swaps, even USD forks.
 

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Discussion Starter · #9 ·
Allready looking.....I assume those wheels are fat pigs, just need to find soomething local that works. Finding parts on this island is one of the only down sides.
 

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Discussion Starter · #10 ·
Winding down finally on the chop and getting at this.

Decided I wanted a single sided swingarm. But I dont want to buy anything, not my style. So I've got a plan. Uses an off the shelf Jeep unit bearing, a modified axle shaft for the sprocket flange,
Tube and plate is easy, so I'm gonna mock up the bearing and see what we've got. Thinking a simple hat to a wilwood rotor, and I can use another car wheel on this one, 17 likely, with a 5 on 4.5 bolt pattern. Real common, no exotic wear parts. Should be cool if it works how I've got it planned. Cutting the tail this weekend too so I have something to play with at home in the evenings.

 

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Discussion Starter · #12 ·
I think I got this all figured. I started programming it with inverted forks. And then I realized that means spending all that money. Well, that, and I like to build everything. I think the girder could be very cool with a little work.





 

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Discussion Starter · #13 ·
Messed with some aluminum today. Dont usually use it, but I'm thinking about weight. The kid wants me to touch up the welds so she can just polish it. Thinking I might just flat black everything.

Had some foam left over and made a seat pan too. Now I just need to mount it.




 

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Discussion Starter · #15 ·
I've got a feeling it will change a little along the way, I had the tail programmed really plain and blocky, and once I started cutting plate I just liked this better.
I'm really torn over the front end at the moment, I want to do the girder, but I know the USD forks would perform better.

Hopefully going to start on the swingarm this week, start getting it mocked up so I can sort out the sprockets and wheel, gives me a little time to decide what I want to do up front.
 

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Discussion Starter · #17 ·
While I'm messing with parts, it was a good time to crunch some numbers on the girder.

The more I played with it, the more I was happy with it. And heres the reasoning............


Beyond the fact that I get to build it, hydraulic forks are flawed. The trail is constantly changing.
I play with this kind of crap all the time in the 4x4 world.
So first thing and easiest, is to make the trail consistant.

Hydraulic fork first.

While it doesnt seem like much, if I can improve on it even a little, why not.

Black numbers are ride height, Green is extended, red is compressed, and blue is compressed with the ass end unloading. Basing it on 2" of compression, 2" of extension, and 2" of the ass picking up. Not perfect numbers, but its getting me in the ballpark.
4.5" of trail at ride height. jumps to 5.09 at extension, 3.95 at compression, and 3.26 with the ass unloaded.



So I figured since it worked good at 4.5" of trail stock at ride height, I'd run with that.

This proves why girders have such a bad name. 99% of them run parallel and equal length bars. And the numbers are a drastiic change.
4.50 at ride height, 3.35 at compression, but jumps huge to 7.24 at extension...



And after some numbers, some drawings, and a lot more drawings, I've got it a whole hell of a lot closer. Close enough that I'm going to program it out in 3d anyways.
4.6 at ride height, 4.50 at extension, and 4.50 at compression.........



And yes I know that internals on USD forks are better. And I'll need a good shock to take advantage of it, but I should still be able to make this perform real well.

Next I'm going to mess with my link calculator and see if it works to calculate antidive on this thing, should work, but I've never tried.
 

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Are you planning on using the stock tank? It looks like you can weld Alu pretty well there, so a new Alu tank would let you reshape it to match the tail, and shave some weight.

Girder forks are awesome for exactly what you mentioned. Maintaining trail in corners under breaking. I would venture a guess that you could get a single shock for your girder that could preform just as good as your average telescopic forks. And from what it sounds like, you have a wide base of vehicular knowledge, so you might be able to find a shock from a quad, or car or something else, respring, revalve and have a cheap solution.

I really respect your plans to use the jeep bearing and hub for your rear single sided swingarm. I love that kind of stuff, that's what makes this forum my favorite place. People that take what they have and make what they want no matter what.

Bob
 

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Discussion Starter · #20 ·
I was actually looking at the tank night before last thinking about that. I want to pinch the back end of it and change the lines a little, just need to get the inspiration to do it. Thinking about changing the frame just a little at the same time though, havent quite made up my mine yet.

Was looking at Fox shocks last night. I know how to rebuild coilovers, so I could adjust the valving until its right. Down side is as a track bike it would never perform wuite as good as a set of hydraulic forks, part of the advantage of a big shock(hydraulic tubes) is the fluid capacity that keeps the temperature down. On the other hand, this will never be a track bike, so it shouldnt really be an issue.
I can wait to put the brackets on for the shock and tune the travel to get the ratio close to something that works, the closer I can get it to 1:1 ratio, the better it will work to keep heat down, and easier it is to tune.

And the swingarm is just the way I am. I'd rather spend 200 in material and 40 hours, than spend 1000 to get something production. Single sided swingarms have always intrigued me, and I think this is the easiest way to give it a try. I've got a couple coming to me as mockup pieces, so the way I see it, I'll only have about $40 into it to try it out at least, and if it all lines up right, and I can source the right sprockets without an issue, then its simple to put it into action. Planning to mock it up with a stock steel wheel, but off center a little to the left and with a 230, I can get a lightweight forged aluminum 17, and run a 200-230 and center the wheel with an aluminum wheel spacer.
 
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