RPM fork valves Versus Late model USDs (??R1 et al)

[nurse]

Winter is closing in and although warm and pleasant at the moment it wont be long before the cold, wet and windy weather kicks in and many of us tuck our rides away till somewhere around April.  We might get the odd dry and sunny day in which case we will get out but personally given that i live in a very rural area, all the mud, salt and crap on the roads just makes it not worth the bother!!

Therefore i tend to switch on the heating in the garage and get tinkering!!  This is the time of year my 'moditis' gets bad!

So im generaly wondering about some USDs.  Now i know and have read alot of the stuff about the older USDs from the yzf-750s and some of the 1000exup models and am aware of the historical pros and cons, but more over in the UK these are now really rare and even rarer in a tidy condition!
I was more thinking about some of the later stuff R1s, MT-09 etc (there are a lot more of these knocking about and plenty with upgrades making OEM front ends redundant, or damage that has left the forks untouched).

There is part of me that thinks 'oh just leave it and ride it' but 6-7months is long time to just look at it every time i walk past it to the spare freezer!! So havnt made my mind up for definate yet.

Does anyone know of someone that has undertaken this type of transplant?
If so how does the ride and handling/performance compare to the RPM fork valves (already insitu!)?
What options could i think about?
The main thing that jumps out is weight.  The Fj is no lightweight and many of todays bikes are lighter than my wallet just before payday, therefreo is thier capacity to handle this extra weigh going to be a restricting factor?
There will other issues clearances, speedo etc etc....

All thoughts welcome. 

[FJ1100mjk]

For starters, conngratulation on your promotion at your workplace. I assume with your promotion, that you now have greater disposable income for mods to your FJ. And that's nice.

If you're serious about USD forks, do a search on Axiom-r (Tim). From what I've seen of his bike, he did the conversion properly, and it's documented well, but buried in the past somewhere here.

Can't speak for RPM valves, but if you've followed their glowing reports, there definitely worth considering too.

Good luck.

[giantkiller]

I used 2008 gsxr 1000 front ends on both my 86 and my 89. Chose this front end because. Several of my friends raced them and they said they were over sprung(too heavy springs) stock. So I thought it would be good for an Fj with me 280lbs. it's perfect. In fact I had someone who worked for a suspension co. Help me set the fork's and Honda shock. And he softened the settings. Also had my neighbor, who was 3rd in points for 2years superbike @ Elkhart take it for a spin. And he came back with a big grin and said " I don't know what you did but you somehow got it just right". He said "it turns in easier than my race bike" (2008 gsxr1000).

I can't remember how much. It think it was almost 10 lbs lighter than the Fj frontend. I weighed all the Fj parts and the gsxr front end. Wheels fenders everything clippons.

Axiom-r has a good write up with pics of r1. Mostly the same .

Condensed version: press out the stems from the triples. Add weld around the bottom of the Fj stem. To build it up. Machine it to fit the gsxr bottom triple. Press it in. Make a spacer for the top of the stem. to fit the gsxr top triple. Make extensions for the top of the forks (made mine a little longer so they would stick up past the triple). I used the gsxr clippons. Cut off the bars so you just have the round clamp part. Make risers out of 1x" 1 3/4" aluminum bar stock. Make bars out of 7/8" round aluminum bar. Drill and tap for Fj bar ends. Weld them up. Get custom spiegler hoses. use the GPS speedo axiom found or use a digital speedo that reads a magnet like I did. My digital dash is 2.8lbs llighter than stock.

[Flynt]

All thoughts welcome. 

I didn't do the conversion, but Wizard has the YZF750 forks.  They are compression and rebound adjustable KYBs and the conversion is well documented (search Marc Rittner).  They also have custom internals from GP suspension, so they might not be the typical USDs...  OK, that covers the disclaimers.

I find them to be exactly what my '92 FJ needs to compliment the later model's stiffer frame.  I also have the Thunderace swing arm and a fully adjustable Ohlins shock.  The resulting bike feels comparable to the more modern delta-box designs and it noticeably stiffer than the '90 I had as well as the '86 I've ridden a bit (RPM equipped F and R).  the forks are rock solid and exhibit no flex that I can detect under heavy braking.  They also give me the 320mm rotors and, combined with R1 blue spots, true 1 finger brakes that modulate nicely and will "stoppie" if you like (haven't tried this, but my index finger alone does all the front brake actuation).

The RPM valves are the much easier, cheaper, and by most accounts transformative mod you'll find to make your FJ better.  I have ridden them and they work as advertised I'd say...  plush and controlled in any circumstance.  I'm admittedly a bit of the dinosaur however and I really like the C/R adjustability to get the feel just where I like it...  Kind of on the stiff/sporty side  IMHO the USDs also look awesome and visually makes the FJ look more modern if that's a goal.  The forks, combined with the short swing arm and raised rear, also make Wizard turn more like a sport bike (telepathic feeling with very little inertia).  Not sure how much of this is attributable to the front vs the rear, but the package overall is spot on for my preferences and does a great job of keeping the beast of a bike under control.  I also ride 2-up mostly and the stiffer forks may be part of the reason the bike feels just like I'm solo...  doesn't impact my pace much at all.

Those are the thoughts I have for you...

Frank

[giantkiller]

Oh yah if you use the clippons. And make the extensions longer. You have adjustable bar heights. Just slide the clippons up on the extensions for touring. And back down for the twisties.

All together pretty simple. Did the 86 fj1350r (my hot rod). Then did the 89 ( my touring/two up) the same way. My digital gages are red on the 86, blue on the 89.

[Dan Filetti]

I'm still a bit surprised no one has taken on grafting a set of Big Piston Forks onto the FJ.  Seems that'd make many of the same improvements Flynt raves about.

Guessing there are engineering obstacles big enough to prevent the attempt? 

Dan 

[giantkiller]

I looked at the big pistons. The body of the forks steps down too soon. If you put the extensions on that the Fj needs. The forks diameter steps down and the bottom of the triple is too far up into the thinner part of the forks.

[nurse]

Been looking about.  Found some other options, ironically most of them in The US!!

Any thoughts on USDs from sources such as Fz8's or Fz1s's??