GSXR FRONT Fork/Rim modification

[eeshed]

Dear community,
Earlier this week I spoke with a community member who suggested an alternative option for updating a 1985 FJ1100 front-end. The suggestion was to use a 17" GSXR 750/1000 front inverted suspension/rim breaks. This GSXR new alternative option stacks against the option of replacing the 1985 FJ1100 front with a 1989 FJ1200 Fork/Rim with a rebuild of RMP Valve/Springs/New seals.

Has anyone done this modification and could share their experience? What may be the parts/steps/issues related to using the GSXR parts for this update? 

Here is a summary of questions about this upgrade option:
1) Is it possible for using the GSXR parts? Any specific year I should be searching?
2) What parts am I looking for a complete  solution?
3) Any significant weight advantage?
4) Will the GSXR rim be a 3" or 3.5"? Any advantage with respect to tire options?
5) Any experience with respect to performance between a GSXR tunes forks and FJ1200/RPM parts rebuild?

Thank you,

Eyal

[movenon]

Dear community,
Earlier this week I spoke with a community member who suggested an alternative option for updating a 1985 FJ1100 front-end. The suggestion was to use a 17" GSXR 750/1000 front inverted suspension/rim breaks. This GSXR new alternative option stacks against the option of replacing the 1985 FJ1100 front with a 1989 FJ1200 Fork/Rim with a rebuild of RMP Valve/Springs/New seals.

Has anyone done this modification and could share their experience? What may be the parts/steps/issues related to using the GSXR parts for this update? 

Here is a summary of questions about this upgrade option:
1) Is it possible for using the GSXR parts? Any specific year I should be searching?
2) What parts am I looking for a complete  solution?
3) Any significant weight advantage?
4) Will the GSXR rim be a 3" or 3.5"? Any advantage with respect to tire options?
5) Any experience with respect to performance between a GSXR tunes forks and FJ1200/RPM parts rebuild?

Thank you,

Eyal

IMO I would go the '89 route......  That's my vote.
George

[giantkiller]

Yah. I've done it  with a gsxr 1000 2008 complete front end. I think the 2007/2008 are the same. I used this front end because a friend who races one said they are over sprung and alot of racers are actually putting lighter ;springs in them.  You will  want to get a complete front off of fleabay. Wheel brakes fender all the way up to the clippons and controls . The first $700 the second one for $850.

Press the stem our of the fj triples. Add some weld around the bottom of the fj stem. Then machine it down to fit the gsxr triples. Them make a spacer to fit the top of fj stem to the top gsxr triple. And then a washer  for the stem nut.
Then make extensions for the forks. I over engineered mine way heavy duty.
Then take the gsxr clippons and turn them over. Cut the bar off, so you have just the clamp ring. Make risers to match the fj risers out of  rectangular aluminum bar stock. Make the bars out of 7/8" round bar stock (I made these with a jigsaw and a belt sander. All the machine work for everything else was done by a shop)
Custom braided brake and clutch lines. And you are done.
Oh yah the reason you turn the clippons over. Is because on the gsxr they mount under the top triple plate. And there is a locating knob. Just drill the holes in the top of the triple to keep the bars in place. (Drilled the locating holes after I got the bars done to make sure they were in exactly the right position)

I weighed all the fj components against the complete gsxr front end. And if I remember right it was like 8lbs lighter than the fj parts
but probably more than that was removed from unsprung weight since the majority of the weight for inverted forks is on the top

So what do you get for all this work
a lot less unsprung weight
much stuffer front end(less fork flex)
Less weight overall
way better brakes
great choice of tires
Newer cartridge valve technology
and most of all you get the chicks!!!

[racerrad8]

a lot less unsprung weight

Dan, what was the unspring weight of the forks you installed?

Also, do you have the total investment, including the custom parts and machine shop work required for the conversion?

I am interested.

Randy - RPM

[Pat Conlon]

I am interested.

Has the earth shifted on it's axis?

[racerrad8]

Has the earth shifted on it's axis?

Nope, I just cannot imagine a steel fork tube slider that is longer than the lower leg of the FJ forks can be lighter.

I weighed the FJ sliders this morning and the two of them combined weigh 3.2 lbs. I just wonder if Dan took the weight of the sliders to determine the actual unsprung weight. I am going to assemble all of the parts, including the wheel and brake caliper later to see the actual weight of the unsprung items of the FJ forks. It would be good to be able to compare the two.

I am not even going into the debate of the other perceived "benefits" of the USD forks or the amount of time & money required to install them.

No fear Pat, I am going to send you out on my RPM outfitted bike when you come and get yours. I want you to feel the difference and I too think you will then understand the ultimate performance of the RPM fork valves in the FJ forks.

Frank (flynt) is going to get to feel first hand this weekend the transformation of the complete RPM suspension package, I will make sure posts up as well his findings.

RPM fork valves; drop them in, cut a spacer, fill with oil and you will not believe the ride...

Randy - RPM

[giantkiller]

No Randy I didn't take them apart. But I know that unsprung weight  and  rigidity. Is the reason the manufacturers spent all there money developing them. And I don't remember the exact weight difference of the  total weight ( I did post it  right after I did it)  I think it was 8+lbs.  I remember thinking it was going to be a lot more after lifting the complete gsxr front end vrs just the fj forks. In fact it was my machinist who pointed it out too me.

I would have gone with your valves. But my bike had been sitting so long my masters  and calipers in fact anything that had to do with brake fluid was toast.  Including the antidive. I could have spent $4-500 fixing and replaying everything. Then I would  have had to get you're valves to get them to perform. And get rid of the antidive. And find the right wheel. Like I had too for the back.(newer gsxr wheels a plentiful)
I did all the design research and all the work except actual machining myself. And a guy at work has a son who does my machine work at a reasonable price. I came in at just under $1200 including new bearings, tire and custom brake lines
So expensive yes. A lot of (fun) work yes.
If I had a good front end I would have gone with you're valves...  Well maybe not I never make the smart choice. I like jumping in and figuring things out.

[racerrad8]

No Randy I didn't take them apart. But I know that unsprung weight  and  rigidity. Is the reason the manufacturers spent all there money developing them. And I don't remember the exact weight difference of the  total weight ( I did post it  right after I did it)  I think it was 8+lbs.  I remember thinking it was going to be a lot more after lifting the complete gsxr front end vrs just the fj forks. In fact it was my machinist who pointed it out too me.

I would have gone with your valves. But my bike had been sitting so long my masters  and calipers in fact anything that had to do with brake fluid was toast.  Including the antidive. I could have spent $4-500 fixing and replaying everything. Then I would  have had to get you're valves to get them to perform. And get rid of the antidive. And find the right wheel. Like I had too for the back.(newer gsxr wheels a plentiful)
I did all the design research and all the work except actual machining myself. And a guy at work has a son who does my machine work at a reasonable price. I came in at just under $1200 including new bearings, tire and custom brake lines
So expensive yes. A lot of (fun) work yes.
If I had a good front end I would have gone with you're valves...  Well maybe not I never make the smart choice. I like jumping in and figuring things out.

Thanks Dan, I wasn't questioning why you did the conversion, I understand the moditis factor of the FJ. I was just hoping you had gotten the actual weight of the unsprung portion of the USD forks so I could do a comparison to the FJ components.

I did see the 8lb difference, was that just the forks along without the wheel & all the other associated parts or the complete front end triples & all?

Thanks for the information and glad you enjoyed the journey of the conversion.

Randy - RPM

[giantkiller]

It was complete wheels triples every thing. I do remember that there where a few thing's missing from the fj stuff I can't remember what probably a few bolts and the brake components were dry. The gsxr front I just took it off my bike and wheeled it into work by the handle bars. Every body thought I was nuts. The fj parts I gathered everything I could find. That's why I was missing some things. But like I said I really was kinda disappointed. I thought it was going to be a lot more.

Randy I think you and your products/services are unmatched. I don't think you ever sent me an invoice for the T's and the second regulator?  Or is my brain damage so bad that I don't remember paying you?

[racerrad8]

Randy I think you and your products/services are unmatched. I don't think you ever sent me an invoice for the T's and the second regulator?  Or is my brain damage so bad that I don't remember paying you?

Its the 1st one...

There is a sticky note on the file cabinet next to the desk.

Randy - RPM

[rktmanfj]

It was complete wheels triples every thing. I do remember that there where a few thing's missing from the fj stuff I can't remember what probably a few bolts and the brake components were dry. The gsxr front I just took it off my bike and wheeled it into work by the handle bars. Every body thought I was nuts. The fj parts I gathered everything I could find. That's why I was missing some things. But like I said I really was kinda disappointed. I thought it was going to be a lot more.

Randy I think you and your products/services are unmatched. I don't think you ever sent me an invoice for the T's and the second regulator?  Or is my brain damage so bad that I don't remember paying you?

I'd guess that a significant part of that 8 lbs. was at the wheels.

Someone measured the difference between the YZF600 and FJ1200 rear wheels at 6 lbs... attributed at the time to advances in casting technology.

[giantkiller]

I just looked back at my old post. The difference was 9.8lbs. I was missing the rear part of the fender, the brake system was dry, and the tire was completely bald for fj stuff. And the tire on the gsxr wheel was brand new. So I guess 9.8lbs is a lot. But I remember thinking it was going to be more.