Pictures of the inverted KTM85SX forks for my Z

[Billy Golightly]

Ok, heres the pictures of the new forks.


Pic #1: One of the '04 KTM85SX front forks leaning up against my 'mockup' Tri-Z. Camera was having a hard time with the low light in the shop this evening so its a little bit blurry. Checkout how nice and fat the lower portion is.... :drool:

Pic #2: Both forks side by side. At first glance the 85SX forks look to be shorter then the Tri-Z forks, over all they are. Once you look closer though, you'll realise that from the top to the axle mount hole is the same :cool:

Pic #3: About the same as #2, better lighting.


Pic #4: I probably took 25 pictures trying to get this to show up and this was about the best one. This is the metric measuring calipers over the Tri-Z forks. The calipers are set to the same size diameter as the KTM forks at the small end which is 43mm (Coincidently the same size diameter as the conventional CR500 forks). Z forks are 35mm in diameter, so the KTMs are quite a bit larger.

Pic #5: This is a picture of the axle holes, I haven't took the Z axle out yet to compare the two exactly, but I dont think there is as big of a difference as i was thinking. Not sure what I'm going to do about wheel bearings yet. Probably order a set of KTM bearings and see how they fit into the Z hub and then go from there with possibly boring the hub out to fit a larger OD bearing or making an aluminum bushing and welding it in, depending on which way I have to go.

Pic #6: The top clamp that I got with my CR500 laegers conversion parts. The clamps I'm making will be based off of this. I'm making some steel ones to start with and then will make aluminum ones in this same style at a later date. Hopefully CNC machined billet ones in the future.

[Billy Golightly]

Heres the last ones of the brake calipers.


The nice new shiny silver looking one is the stock KTM85SX front caliper. It'll of course fit up nice with the forks, but as you can see its very, very small. Even though its a dual piston design instead of a single like the Z caliper it probably has half the pad area, so I know it wont brake near as well. I'm probably going to have to make up some custom bracketry to make the Z caliper (Or possibly something else) fit when it comes time. Depending of course on what needs to be done with the brake disc and stuff to keep the alignment right.

[Kintore]

That is awesome Billy! I am looking forward to seeing this massive conversion move forward. I would like you you said use the Z brake system other than the SX one. Looks like this could turn into a very good project, I am very interested on how this will turn out. Good luck Billy!

[Lots_Of_Nothing]

Bill, If it were me, I would not put that Z caliper on it. Your gonna have this high tech frontend on it, the least you can do is update the braking system. You allready have all them new nissin masters.. Look on ebay at streetbike calipers. Awesome looks and awesome performance. Plus you can usually pick them up at not too bad of a price.

Good to see the project taking off, I think you have put the most thought into the frontend conversion then anyone else (including the people who have done it).

[Blown 331]

When I first saw your thread title I thought you were puting forks from an 85 250SX on a TRI-Z, I was like WTF?

[Huffa]

When I first saw your thread title I thought you were puting forks from an 85 250SX on a TRI-Z, I was like WTF?

Same here! :wondering

[Billy Golightly]

@ Kintore:

Thanks! Its gonna take some time and some serious tinkering but I think I'll have it worked out. The first set of tripples i think should be done in 3-4 weeks. I was thinking about 2 weeks but my dad seized the lathe today working on the round clamping pieces while I was taking my mom to the chiropractor this morning. Hopefully he can get it unstuck and we can get back working on it. I have to order some holesaws and a few other misc things either this week or next to help get the tripples setup.



@ Jared:

I agree with you on the caliper thing. It needs to be updated to something else. I hadn't thought of a street bike caliper, but your right that would be pretty cool and they do work good. The only thing is, their kind of big, might have a problem with it fitting in the wheel. My thought was, that since I know the KTM125SX front forks are the same diameter as these but longer, maybe one of the front calipers off of it or something larger (Like a 250+) Would work too. Its kind of a long shot but it might work. I also just realised I have an old CR500 front caliper off of the inverted forks I first started messing with back on the 500X. Thats a pretty beefy caliper and it was a twin piston design. Seems like the mounting holes were similar but I'll have to investigate that a little bit more.


@ Huffa and Blown331

:lol: I never thought of that, I guess I should change the title huh?

[Derrick Adams]

Billy, since your working on the front anyhow and building new triples, maybe you should think about changing the rake. Wasn't the long rake on the Z what made it handle less agile than the other 250's? I know Tim had told me that he runs his forks up in the triples for that reason (pretty sure). Might be something to think about.

[Billy Golightly]

Derrick, I was actually thinking of increasing the wheelbase slightly (Moving the forks further ahead) so that I would retain my same turning radius as I do now. If I left them in the stock posistion, I would have less turning room because of the larger diameter forks. Changing the actual rake in the clamps would be tricky...you'd have to mount the stem in the bottom and top clamps at some sort of an angle. It could be done I guess but I'm not totally sure how to go about doing it.

[bigyellow4x4]

could you give us some more pics of the steel clamps you have and the thinkness of plate used please

[sblt500r]

i might have missed something but why use 80 forks? won't they be to weak or soft? a triz weights a bit more than an 80 mx bike! unless you plan on changing the springs

[Billy Golightly]

The 85 forks are already the correct length. Any thing from a 250 or 125cc bike has to be shortened. Yes, I will have to change the springs to a custom weight but thats alot easier then tototally dissasembling the forks and cutting down the fork tubes, the springs, the dampening rod, the fork cartridge, re-tapping the end of the dampeing rod, re-drilling the valving holes, ect ect ect.


The steel clamps are not done yet, but when they are I will post some pictures. They are going to be pretty thick and heavy to start off with.

[LonesomeTriZ]

What is the travel difference between the two fork set ups?

[69HemiGTX]

What is the travel difference between the two fork set ups?

Tri-Z - 10.0 inches

85SX - 10.83 inches


Not much basically, but the quantum leap in damping technology is worth it. Not to mention it's gonna look trick! :w00t: I've seen an 85 250R with YZ80 forks, and it was sweet.

[LonesomeTriZ]

Food point. I was considering YZ 80 forks myself. But it looks as though this way is a little better in some ways.

[Jeb]

Good job Billy! The stock 85 Z forks look week compared to those USD's. I didn't realize 80cc MX bikes these days had such heavy duty forks.

Remember your going to be running slightly different geometry due to the leading axle design of the USD. Or are you planning on turning the forks around for trailing axle?

I can't wait to see the finished Z because it will look right. :beer

[Billy Golightly]

These are the only forks I've found in the 80cc range that are larger then the Z ones. I think I did find one pair that was 39mm but all the rest were puney 34-35mm in diameter which wouldn't even be an upgrade IMO. I'll probably keep the leading axle design for now. It wouldn't be hard to switch it around if i so desire at a later date though. Its definetly gonna be some R&D going into these to get them done right, but when I'm done between them and my works rear shock I ought to be able to jump off a cliff :lol:

[3WheelsForever]

Looks good Billy, Im in the process of getting a set of inverted front forks to put on my 426. I need the extra length since Ill be running a 10 inch front rim and 20 inch tire :)