CR480: 98 RM Fork Conversion Questions

pm me if your looking for forks i have six sets, i know nothing of your conversion though i used them on late model yzs, and rms

I will point out one issue with doing this. Not sure if yours is an 82 or 83 but that bike is a hot setup, especially the 83, for the post vintage classes for AHRMA, AMA, etc. If you put modern forks on it you will not be able to race those events. Maybe you aren't planning on that? You stating that you want to retain the drum has me thinking perhaps you are? If you are doing it to keep it and not ride PV events good upgrade. Believe it or not that upgrade would probably decrease the value of the bike because most guys looking for one want to race vintage and or they want it "the way it was"

I race an 83CR250 with stock forks with the RaceTech emulators installed, makes them like a cartridge fork, and they work great. I weigh around 200 lbs. I too was hearing about the 87 conversion but all of my research said the emulators would get you near what those forks would do. Some will argue that but I would go that route over 98. I have never heard of it happening but someone could even protest that because they aren't "period correct" but I doubt it.

I do know if you show up with upside down forks you'll be watching the races......

Are your current tubes in good shape?

I have to ask the question, why? What are you hoping to achieve?

I can see why you would want swap to the '86-'88 forks. It's a relativly simple swap, but '98 RM forks? That's a LOT of work, a lot more than either of the 2 ways to fit CR cartridge forks.
And at the end of it you probably won't have a better fork, the '86-'88 CR cartridge forks are possibly the best conventional forks ever made.

Stevie

Stan... I like your thinking!
A 480 is certainly not lacking in the motor department.. The only areas it's "lacking" is the suspension and brakes.

If you are not fussed for keeping it "legal" (not sure exactly how your rules work over there!) I would just throw a much later front end on. Pick which year forks you want/ like and bang the whole lot, brake and all, on. Any Honda front end should fit with minimal work, maybe at most the maching and fitting of a new steering stem. That would sort out 2 of the main issues in one easy swap. I'd pick the 47mm twin chamber forks.

At the rear I'd fit a new Works Performance Shock. That would sort out the rear end and boom!! You'd have a very competative 450 eater!

Doing a rear disc conversion on a 480 would be hard as the brake and drive are both on the same side, but a well set up drum on the rear isn't really much, if any, of disadvantage... unless you want to race SX on it!

If you want to keep it period/legal then swapping to the cartidge forks is the way to go. They would fit straight into your original yokes, swapping the drum over is pretty easy. Theres 2 ways to do this, custom bottom bolts/washers to secure the cartridge damper rod end into the non-cartridge fork lowers or, as we do, cut the disc mounts off the cartridge lowers and weld on a lug for the drum. (there a few more bits to the conversion, but I won't go off topic!)

There are aftermarket yokes for the 43mm forks aswell. Ours, and couple of other companies do them.

You could maybe modify a '79 CR250 tank if you want to get something alloy and paintable?

Our rules over here mean the '83 480 runs with bikes up to '89, and we can do pretty much what ever we want.... BUT, we can't use forks later than '89, (I dont get it!!) so I would be looking at swapping an '87 CR front end on or doing a lot of work with '89 CR forks to actually make them work! along with a Works shock and maybe a new swing arm...

Damm it I want to build one now!! I'm using a 480 for my next twinshock racebike anyway... but now I'll need 2!!

Stevie

Send another E-mail Stan, My Dad deals with the E-mails so it's probably on his desk in his "to reply to" pile!

I installed the RM forks on my 83 kx125. I know they wont be legit for AHRMA events. My plan is to find someone with a lathe to make reducing spacers so I can slip the 87 honda forks I have for the one or two times a year I need them. This is my only bike so I wanted good suspension. I don't ride ahrma events every weekend

Fitting them wasn't them mess it could have been. My kx stem was a little smaller diameter than the Suzuki stem. But I bet your stem will press right into the RM clamps.
I found a set of Applied billet triples. I thought they looked trick with 6 pinch bolts on the lower clamp
My bike had a disc stock. So i didn't have the problem of a brake stay for the backing plate like your bike. Ive seen where someone machined a bracket that bolted to the caliper mounts . It looked clean. Id rather do that than weld a lug on. It would be nice if you could come up with a brake stay like on Simons or a Maico that bolted on the front of the fork.
I laced up a YZ front hub. I chose that because in my wacky mind the big spool hub with no casting ridges looked Works to me . But you are going go have to make some kind of reducing sleeves because Im pretty sure the old CR axle is a smaller diameter than what the newer RM used.
I got lucky with the fork stops. They lined right up. Its possible you may have to tweak the stock stop on your frame.

I have a good friend with a 480 like yours. He slid 87 forks into his stock clamps. Runs a disc too. He loves his bike. Not too many people describe thier bike as a pleasure to ride as he does. He had to go to someone else to have his Ohlin shock valved. But he almost always loads the 480 to go riding over his YZ250

Stan - I actually had no idea Suzuki switched back to conventional in 97-98 I just assumed they would be upside down.. 95-02 was the only time since 79 that I was out of bikes - new wife, new house, 2 new kids all kind of make that happen! Even still you probably would have someone point it out if you were leading the pack I agree.

I actually found the a period correct Ohlins shock and Simons link for the rear on mine. I had Steve Marpes completely rebuild it - works great. To your point I let a buddy that rides modern, pretty fast, ride mine and he thought he could go as fast as he could on his KTM.

As info there is someone over on Marks vintage selling an 83 480 head with a built in compression release on it. He wants $85. I have one friend with one and one without one - it's a great upgrade based on watching both of them start one.

If one were able enough to machine up a collar with a drum brake boss and adapt these forks
to a vintage bike using the triples why would it be an issue ? They are still regular conventional style forks right ?
Is there still good tech support for these forks as well as aftermarket parts availability ?
There are a few nice 125 RM forks on ebay that would be great for a smaller bike me thinks.

http://www.thumpertalk.com/topic/544779-97-suzuki-rm125250-forks/

After all they are Showa right ? hehe
I'd be up to trying ! Anyone done it ?

Those forks are sweet, and they're not conventional forks like everyone seems to think, they are twin chamber conventional. You find kids swapping them out for open chamber upside down forks all the time. lol I bought a 96 RM125 for my kids 1st bike and that was the sweetest chassis I ever rode.

The emulators work amazing.

It'll be tough to pass tech inspection with those forks though, you'd have to do a lot of grinding and strategic sticker placement.

There's an '83 480 on ebay right now with front and rear disks.
You may be able to ask the seller more about it, however I have spoken to him about this bike about a year ago and I am pretty sure he bought it with the disks already on it and probably wouldn't know exactly what was used to do it. That whole setup was the deal breaker for me, I wanted an AHRMA legal 480.
Probably can't hurt to ask him though.

i have a 98 RM250 with those forks on it and I have owned an 83 CR480 with full Race Tech fork/shock (will set you back just over $2000.00). I had thought about doing the 98 fork mod on my 83 as well, but having raced with the Race Tech set up for a couple of years (on all of my bikes), i would not waste my time with this conversion because the set up would be illegal in AHRMA. Heck, why not just add a set of USD forks instead. I will tell you this, I did put a set of 46mm 89 Suzuki RM125 forks on my 1980 Suzuki RM125 (years ago) and they work great, but required a lot of machining to get the DL shoe front brake to work but I did get it to work (see below photo).

By the way, I did that 89 RM125 fork conversion on my 80 RM125 years ago (maybe 2006), so that was long before I ever used full Race Tech suspension and now Race Tech is all I use exclusively (Except the Fox airs on my 76 CR125, but i am using Race Tech gold valves in the Simons forks on that bike too).