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Fork swap problem!!

  • Thread starter Thread starter spots25
  • Start date Start date
S

spots25

Guest
I'm attempting to swap the forks of a '84 Kawasaki GPZ900R (ninja) onto my '78 GS400. I pulled everything apart, and did some measuring, and checked http://www.pro-flo.com to check my work.

From pro-flo, the Kawi takes:
Upper: 25x47x15
Lower: 28x52x16.5

and the GS takes:
Upper: 25x48x16
Lower: 27x48x14

Thus one would conclude that I need:
Upper: 25x48x15-16
Lower: 28x48x14-17

Based on my measurements, I determined that I need:
Upper: 25x48x16-17
Lower: 28x48x15-16

Now my problem comes that Allballs doesn't make what I need. Whats a guy to do?

Also, my new steering stem is about 2cm longer than the old one, is that going to be a problem, or just a clever use of spacers?
 
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About the only advice I can give on this is take the triple and get the races out of the steering stem and head for a bearing shop to see if they can fix you up. You can fins a way to work around stem length.
 
also, FWIW, the GS400 has ball bearings, and I destroyed the lower bearing on the Kawi
 
spots25 said:
also, FWIW, the GS400 has ball bearings, and I destroyed the lower bearing on the Kawi
Click to expand...

You're best bet is still a bearing shop to see if they can match you up. There are conversion kits to go to tapered bearings.
 
i think there's a bearing shop near where I work, i'll check it out tomorrow. In the mean time, whats the best way to deal with a slightly longer steering stem?
 
spots25 said:
i think there's a bearing shop near where I work, i'll check it out tomorrow. In the mean time, whats the best way to deal with a slightly longer steering stem?
Click to expand...

Without seeing it I can only suggest a couple of things. One is to have the threads cut further down the stem, the other is to see if it can be pressed a little further down into the lower triple and welded in place. That's if the lower triple is steel. You might also see if your stem could be pressed out and installed in the Ninja triple.
 
first of all, thanks for being helpful and quick!

I looked at the steering stems, and the GS400 stem is welded in place, whereas the Kawi stem is pressed in place. The part that the upper bearing rides on is machined slightly less in diameter than the rest of the stem, so for it to go down further, it would need to be machined as well... hold on, I just got an idea...

Okay, so the steering shaft on the kawi front bulges out where the lower bearing sits, and right above that has a measurement of 26.7 mm, so if a guy put a 27x48x14 bearing on that part, and put a spacer between the bottom of the steering shaft and the bottom of the bearing, it would be a perfect fit. That extra .3mm shouldn't really matter, should it?
 
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spots25 said:
first of all, thanks for being helpful and quick!

I looked at the steering stems, and the GS400 stem is welded in place, whereas the Kawi stem is pressed in place. The part that the upper bearing rides on is machined slightly less in diameter than the rest of the stem, so for it to go down further, it would need to be machined as well... hold on, I just got an idea...

Okay, so the steering shaft on the kawi front bulges out where the lower bearing sits, and right above that has a measurement of 26.7 mm, so if a guy put a 27x48x14 bearing on that part, and put a spacer between the bottom of the steering shaft and the bottom of the bearing, it would be a perfect fit. That extra .3mm shouldn't really matter, should it?
Click to expand...

I was thinking about your problem earlier and that's what I came up with. Use a spacer below the bearing.
 
Billy Ricks said:
I was thinking about your problem earlier and that's what I came up with. Use a spacer below the bearing.
Click to expand...

and I just found the perfect spacer, my OLD INNER RACE!!! oooh, this is all coming together!!
 
spots25 said:
and I just found the perfect spacer, my OLD INNER RACE!!! oooh, this is all coming together!!
Click to expand...

Is the race going to stay in place. You may want something that is going to be as close to the diameter of the stem as you can get.
 
Billy Ricks said:
Is the race going to stay in place. You may want something that is going to be as close to the diameter of the stem as you can get.
Click to expand...

yeah, i cut the lower inner race with my dremel tool just enough so I could crack it with a chisel, but its still a tight fit
 
ok, how much play between the inner bearing and the steering shaft is acceptable? There is a little bit, but its more than i'm comfortable with before asking. I've got pictures, but photobucket is doing site maintenence and I can't upload them.

There is just a little bit of play. Say, if usual play was like 3/1000", this is like 6/1000" Is that close enough? What should I do?
 
spots25 said:
ok, how much play between the inner bearing and the steering shaft is acceptable? There is a little bit, but its more than i'm comfortable with before asking. I've got pictures, but photobucket is doing site maintenence and I can't upload them.

There is just a little bit of play. Say, if usual play was like 3/1000", this is like 6/1000" Is that close enough? What should I do?
Click to expand...
There's no spec for that as far as limits go. If you can move the triples back and forth in the frame then it's too much. Since they are tapered bearings you need to go ahead and assemble the triple and see how it feels. That slack may get taken up when the triple is put together on the bike.
 
eh, it never did pan out... I got the steering shaft out, and its at the machine shop... i'll get this working yet!! \\:D/
 
Sounds like you are on the right track. Have a custom steering shaft made
 
SqDancerLynn1 said:
Sounds like you are on the right track. Have a custom steering shaft made
Click to expand...

well most of the steering shaft worked perfectly, but i just needed about a 1mm turned off where the bottom race sits. I can't wait to get it back!!
 
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