Author Topic: fork upgrade  (Read 2361 times)

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Offline matzilla

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fork upgrade
« on: January 09, 2010, 07:07:05 AM »
I have been searching for info about upgrading to the newer style forks for my 88. I have a bike wrecker here in the NW that I can get many or maybe all the parts I will need. I am hoping for some input on what will go right on without having to machine anything. Is the stem diameter the same 88 to 04? How about stem height?

Offline ShadeTreeFab

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Re: fork upgrade
« Reply #1 on: January 09, 2010, 07:55:12 AM »
with the frame being the same from 89 & up, they went to upside down forks in 93 i think. its the same clamp assembly from 86 to 92.
head bearings are the same part # 88 and up, might go back further didn't search any more.
i think any fork/clamp 94 and newer would just bolt on. wheel and brakes do not know didn't check.

Offline 500freak

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Re: fork upgrade
« Reply #2 on: January 11, 2010, 04:08:14 AM »
i put inverted forks from a 92 k5 on my 87, and you have to use the rim, caliper, and triple tree.
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Motorrad

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Re: fork upgrade
« Reply #3 on: January 11, 2010, 06:02:09 AM »

Offline don46

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Re: fork upgrade
« Reply #4 on: January 13, 2010, 05:16:26 AM »
If you choose to use K5 forks, it will be a matter of changing the forks and triple clamps, stem should be the same. 88 I think had a smaller front axle (not sure about that) if so your going to have to change your bearings to the newer dimensions of 20 mm. as for brakes I'm not sure.

If you want to mount 250f or 450f forks it becomes a bit more complicated. I mounted a set of 450 triples last night on a 500 chassis, what I found was the stem is to long, no problem press out the stem and away you go, wrong. The 500 stem on the big end is 30mm, the 450 is 30.19mm, I was rumaging through some of my spares and found a stem that was 30.19 on the big end and all the other dimensions were the same as the 500. The stem was stell and I think it came off a older 250 or 500, anyway it fit perfectly. The bearing area is 30 mm same as the 500. on the top I had to make a bushing for the top clamp the stem bore was 25mm and the 500 stem is 23.46mm anyway about an hour later and they wer installed. I plan on running a 450f front wheel so no big deal there, and the brake was already converted to 250f so no issue there either.

All in all about an hours job with the right tools.

This frame was a 2000 500 and the forks used the 500 externals with 2001 250 internals, they worked quite good so that may be another alternative to getting better forks.

Many have said get them revalved, but honestly there is only so much you can do with the stock forks, the newer stuff is quite noticeably better, and of courrse it depends on what your going to be doing to.
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Offline matzilla

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Re: fork upgrade
« Reply #5 on: January 17, 2010, 07:29:51 AM »
I can get a set of 02 250 forks for $100. 48mm. Did any of the 500s use the 48mm forks? Or I can get the 46mm ones for about the same price. Trying to keep it simple as possible. I know I will be running wheel axel and brakes from whatever the forks come from. No issue there. Just trying to figure out what tripples and stem setup I need to find to go with either of these fork combinations.

Offline matzilla

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Re: fork upgrade
« Reply #6 on: January 18, 2010, 02:36:27 PM »
Let me clarify.  I haven't been able to find a full setup from a newer KX500.  I have however been able to find newer K5 tripples and KX250 forks.  I am hoping that someone here might know if the fork bodies are the same for all of the KX 46mm inverted forks, and might they be the same as the later 48mm forks also.  Any advice in this matter is greatly appreciated.

Offline Hillclimb#42

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Re: fork upgrade
« Reply #7 on: January 18, 2010, 03:04:22 PM »
I am not positive of the mm sizes, but I am sure, due to some experimenting on my own, 98 and newer 250 tubes are bigger than my 97 500 forks. My 96 250 has the same size forks as the 97 500.

I have an aftermarket 250 top clamp on the 500 which is solid mount fat bar set-up. It needs a bushing around stem because the 500 stem is a little smaller. Not sure what year 250 the top clamp is supposed to be on, but I am pretty sure its the same as my 250 in every way.

That's amazing, Don. It would take me longer than an hour to explain how to do that, let alone get it done. I need a notepad for all these tips....