There seems to be several options for upside down fork conversions (YZF, GSXR, ZX14). Which seems to be the least
troublesome to do? Are there certain ones that are a real migraine? Do all conversions require pressing
out the pivot tubes, modifying the FJ tube to fit the grafted forks triple clamps and reassemble?
Which forks of a particular front end assembly use the same diameter axle as the FJ1200 ('86)?
Do all of these conversions require using extensions on top of the fork tubes? Thanks for your info.
Barry Edwards has a great site you should review: http://www.fjmods.co.uk/ (http://www.fjmods.co.uk/)
In a nut shell...what I've learned is that the '91-93 FZR1000 USD front end is plug and play.
The YZF750 USD has better forks with external rebound and compression adjustment, but needs the FJ steering stem welded and pressed in the lower YZF triple clamp.
No extension tubes needed on the FZR or YZF forks, they are long enough.
Both the YZF750 and FZR front ends use a mechanical speedo drive which is compatable the the FJ's mechanical speedometer.
The GSXR USD's do need extension tubes and you will lose the mechanical FJ speedometer.
These are entire front end conversions meaning forks, triple clamps, wheel, fender and axle. If you are going the USD route, use the entire front end and don't bother with the skinny FJ 15mm axle or FJ 3" wide front wheel.
Cheers Pat
Hey Pat, thanks for the info. Have there seen any others like R1, RC51, Ducati etc. or is it easiest to
convert using Japanese forks? So, let me see if I'm thinking right. Whatever forks I choose, I need to
match the FJ steering stem diameter to the lower triple clamp so that I can use the factory style tapered
roller bearings? Is that correct?
Yes, now that you mentioned it, there is an R-1 front end conversion I forgot to list (sorry Tim) http://www.fjowners.com/index.php?topic=3148.0 (http://www.fjowners.com/index.php?topic=3148.0)
The steering stem needs to be matched in diameter and length to the FJ's neck, thus it's easiest just to use the FJ steering stem and modify it to fit into the donor lower triple. (excepting the FZR stem which is a direct match to the FJ)
Clear as mud?
IOW, most (if not all) of the modern USD steering stems are larger in diameter (and a different length) and thus won't fit the FJ's steering neck, so the FJ's steering stem is utilized. It's simply pressed out of the FJ lower triple, modified, and pressed into the donor lower triple.
....and yes, with the FJ steering stem, you retain the use of the FJ's oem tapered neck bearings.
If you wanted to use the USD steering stem (and not the FJ's) you would need to do some significant surgery to the FJ frame to weld in a new neck.
BTW, what's your name? We are on a first name basis here....
I'll add another option - but it takes a little work but it does retain the mechanical speedo drive.
Early R1 forks and triples with a ThunderAce front rim. Need to address the FJ stem which is slightly smaller diameter than the R1 stem. If you do a tube handle bar conversion, you don't need extensions. The lower left fork leg has a large lug cast into it (like a built in soccer). The lug is large enough to machine most of it off to make room for the speedo drive, and the ThunderAce rim accepts the speedo drive - but retains the R1 style brake rotors. None of it is bolt in, but it s not extensive. Also, no "recipe" measurements, but it is not difficult to figure out.
This is the setup I've run on the street bike and the race bike for several years.
Thanks for the clarification. Since I have CAD and my next door neighbor has A CNC machine shop :yahoo: I will
probably draw and have a new steering stem turned on a lathe. I think when you put that much heat in the steering
stem (with several passes of welding) you alter the structure of the steel stem. It will probably be cheaper too.
Quote from: FJ-Heretic on October 01, 2017, 04:28:01 PM
I think when you put that much heat in the steering
stem (with several passes of welding) you alter the structure of the steel stem.
Here is my write up on the GSX-R1000 USD fork conversion. http://www.fjowners.com/index.php?topic=16432.0 (http://www.fjowners.com/index.php?topic=16432.0)
IMO, My concerns of altering the structural integrity of the steering stem shaft after welding and turning to fit into the Suzuki lower triple is not very high. Almost all of the
load that the steering stem is carrying is in the near vertical plane....We are talking 8 inches or so of steel. I am not concerned at all.
Fred
hey thanks now i know what to do with that pesky 89 fzr1000 sell it! seriously though this sounds like a good way to go but still begs the damper vs cartridge question. from everything ive heard on this forum the cartridge is the way to go my question as one that never used them are emulators good enough to warrant the older tech?
The best I've found on conventional FJ forks are the RPM valves.
I've had Racetech Cartridge emulators and they are much much better than the oem damper rod forks. No question. The Racetech emulators allow you to use a much heavier fork spring, in the range of .95-1.05 kg/mm spring.
IMHO The RPM valves are a cut above the Racetech valves.
But remember, you still are dealing with the idiosyncrasies and limitations of a conventional fork design. Small 15mm dia. axle and 41mm stanchion tubes on a 550 lb bike with no provisions for rebound or compression adjustment.
For the majority, the RPM valves, .85kg/mm springs and a fork brace are just fine, and truth be told, is a very nice setup.
Although it's always good to remember, the USD forks gets the chicks.
Yes, good advise from Pat.
I too went the route from stock setup (sucked) to racetech cartridge emulators with 1.0 straight rate springs (big improvement)
To Randy's RPM fork valves with recommended springs and fork oil. Actually he sells them all as a package (plug and play). Another huge improvement in handling. I can't compare to the uber sexy USDs (that the chicks really dig) but the RPM system paired with a quality rear shock and fork brace, 3.5" wide front wheel (89 fzr1000) and 5" wide rear wheel (yzf600r) with modern radials definitely brings the FJ into modern day handling.
HTH's... Cheers Jake.
Quote from: FJ-Heretic on October 01, 2017, 12:13:07 AM
There seems to be several options for upside down fork conversions (YZF, GSXR, ZX14). Which seems to be the least
troublesome to do? Are there certain ones that are a real migraine? Do all conversions require pressing
out the pivot tubes, modifying the FJ tube to fit the grafted forks triple clamps and reassemble?
Which forks of a particular front end assembly use the same diameter axle as the FJ1200 ('86)?
Do all of these conversions require using extensions on top of the fork tubes? Thanks for your info.
Take a look at my project write up 'FJ1200 with a bit of Exup ru and a bit of R1 big bang' The exup 1000 almost falls in and with good brakes. Russ
Coming back to this, with the FZR front end, will it accept gold dots from a '03 R1?
Quote from: JohnnyTheCraneGuy on March 14, 2025, 09:00:48 PMComing back to this, with the FZR front end, will it accept gold dots from a '03 R1?
Yes...
I needed to grind a very small relief on the forks to clear the cast hose line fitting on the R-1 caliper body.
You've got to look closely to notice it.
(https://fjowners.com/gallery/49_13_12_09_7_52_07.jpeg)
Roger, I'm currently thinking of pulling the trigger on a set of forks off of a 92 on ebay, I've also managed to find the bottom and top half of the triple tree.
Quote from: Pat Conlon on March 14, 2025, 09:36:05 PMQuote from: JohnnyTheCraneGuy on March 14, 2025, 09:00:48 PMComing back to this, with the FZR front end, will it accept gold dots from a '03 R1?
Yes...
I needed to grind a very small relief on the forks to clear the cast hose line fitting on the R-1 caliper body.
You've got to look closely to notice it.
(https://fjowners.com/gallery/49_13_12_09_7_52_07.jpeg)
Pat, do you think FZR 92 USD fork set is better than Thunder Ace big conventional fork?
Quote from: MarioR on March 18, 2025, 12:13:19 PMQuote from: Pat Conlon on March 14, 2025, 09:36:05 PMQuote from: JohnnyTheCraneGuy on March 14, 2025, 09:00:48 PMComing back to this, with the FZR front end, will it accept gold dots from a '03 R1?
Yes...
I needed to grind a very small relief on the forks to clear the cast hose line fitting on the R-1 caliper body.
You've got to look closely to notice it.
(https://fjowners.com/gallery/49_13_12_09_7_52_07.jpeg)
Pat, do you think FZR 92 USD fork set is better than Thunder Ace big conventional fork?
There is a reason you have never seen an oem or aftermarket fork brace for USD forks.
Yes, USD's are superior to conventional forks...even the TAce beefy tostada (48mm) forks.
Just as cartridge forks are always superior to damper rod forks.
Quote from: Pat Conlon on March 18, 2025, 12:59:24 PMQuote from: MarioR on March 18, 2025, 12:13:19 PMQuote from: Pat Conlon on March 14, 2025, 09:36:05 PMQuote from: JohnnyTheCraneGuy on March 14, 2025, 09:00:48 PMComing back to this, with the FZR front end, will it accept gold dots from a '03 R1?
Yes...
I needed to grind a very small relief on the forks to clear the cast hose line fitting on the R-1 caliper body.
You've got to look closely to notice it.
(https://fjowners.com/gallery/49_13_12_09_7_52_07.jpeg)
Pat, do you think FZR 92 USD fork set is better than Thunder Ace big conventional fork?
There is a reason you have never seen an oem or aftermarket fork brace for USD forks.
Yes, USD's are superior to conventional forks...even the TAce beefy tostada (48mm) forks.
Just as cartridge forks are always superior to damper rod forks.
Pat,
Did some homework and you are right. I was wrong about tostadas.... :Facepalm: They are not bad fork especially they are adjustable but cartridge is way better. Can't cheat on physics.... I have FZR 1000 92 USD full front end still on the bike so this is what I will use moving forward. What will be the best for the top clamp to use/modify in your experience?
Never to late to learn something new...
Thanks
I used the oem FZR top clamp with 7/8" dia. aftermarket handle bar clamps and a FZ-1 bar.
(https://cdn.partzilla.com/cdn-cgi/image/quality=50/MTE/d/7/MjIxMzk2Nw-76ec39df.png)
I used a pair of 2001-2005 Yamaha FZ1 handlebar risers (need to drill the 2 holes in the FZR top clamp out an extra 2mm), with a couple of penny washers sitting in the recesses on the top of the top clamps (and under the rubber pad that goes under the risers).
A perfect mount for the FZ1 bars to get the same hand grip position as the original FJ grips.
Quote from: Millietant on March 19, 2025, 07:01:54 PMI used a pair of 2001-2005 Yamaha FZ1 handlebar risers (need to drill the 2 holes in the FZR top clamp out an extra 2mm), with a couple of penny washers sitting in the recesses on the top of the top clamps (and under the rubber pad that goes under the risers).
A perfect mount for the FZ1 bars to get the same hand grip position as the original FJ grips.
Only one issue that I have, I prefer stock handlebar mounts. Not fan of the FZ1 style. Any other options for US conversion and stock mounting? Or lags are to short to pursue this way??
I made my bars. Using the clamps off of the gixxer clip ons and made them to match the fj clip ons with risers. On my 2008 gsxr1000 front-ends.
I don't like the tube bars either. They look like dirt bike bars to me. Lol.
Quote from: giantkiller on April 08, 2025, 09:53:11 PMI made my bars. Using the clamps off of the gixxer clip ons and made them to match the fj clip ons with risers. On my 2008 gsxr1000 front-ends.
I don't like the tube bars either. They look like dirt bike bars to me. Lol.
How they secured to the tubes? Just with one Allen bolt or there is another to the top triple?
Yes, you are right with the cross bike look.....
It's just the clamp with the one alen. They have a pin that sticks down into a hole. On the top of the triple clamp. I fabricated spacers. So I could raise them up on the extensions. For touring. And remove them when riding the curves. I don't really think the alignment is really needed. If you tighten the clamps they aren't going anywhere. If you're worried about it you could mount them under the triple. Like they are on the gixxer. The pins originally stuck up under the gixxer triple. I flipped them over when I fabricated mine because I wanted to slide them up on the extensions I designed for the gixxer forks. So I could sit up a little. For highway miles.
Motocross bars! The horrors! :sarcastic:
Quote from: fj1289 on April 09, 2025, 05:07:44 PMMotocross bars! The horrors! :sarcastic:
For sure not my cup of tea......
Quote from: MarioR on April 10, 2025, 08:37:54 AMQuote from: fj1289 on April 09, 2025, 05:07:44 PMMotocross bars! The horrors! :sarcastic:
For sure not my cup of tea......
My 2001-2005 FZ1 bars and risers match my original FJ bars for width and can be adjusted to match for height and hand position too - they're not high and wide, like motocross bars. I found the greater range of adjustment in hand position (forward and rearward) helped me find an ultimately more comfortable riding position.
Quote from: MarioR on March 18, 2025, 12:13:19 PMQuote from: Pat Conlon on March 14, 2025, 09:36:05 PMQuote from: JohnnyTheCraneGuy on March 14, 2025, 09:00:48 PMComing back to this, with the FZR front end, will it accept gold dots from a '03 R1?
Yes...
I needed to grind a very small relief on the forks to clear the cast hose line fitting on the R-1 caliper body.
You've got to look closely to notice it.
(https://fjowners.com/gallery/49_13_12_09_7_52_07.jpeg)
Pat, do you think FZR 92 USD fork set is better than Thunder Ace big conventional fork?
Pat,
Since you are modification GURU , this is what I understand for this conversion:
1. Use 92 USD up side down forks with lower triple and custom upper or FZR modified, wheel, shaft, bushings, fender, calipers choice you want
2. What about speedo drive?
3. Alternate option use for an example 96 YZF 750R KAYABA forks (since adjustable forks with 92 FZR lower triple and custom upper or FZR modified. What about wheel than? Shaft probably will be different..... Speedo drive?
4. FZ1 handle bar or custom tall risers mounted under upper
5. Blue dots calipers or 6 pistons caliper tokico
Correct me if I ma wrong. Thanks Pat
Both the FZR1000 and YZF750 front ends use a mechanical speedo drive that the FJ cable plugs into.
I switched from the FZR1000 USD's over to my current YZF750 USD's and here's what I've learned.
Stay away from the YZF750 front end, it takes too much work. You have to use the YZF lower triple, punch out the short fat YZF stem (too short too fat for the FJ steering neck) then weld up increasing the diameter of the skinner FJ steering stem to fit in the big hole in the YZF lower, then press the modified FJ stem into the YZF lower clamp. It's very involved for little benefit . .
The only thing you gain with the YZF750 USD forks vs the FZR USD's are that the YZF forks have external compression adjusters...the FZR forks do not. You set compression on the FZR forks via a shim stack inside the forks. Both forks have external rebound and preload adjusters.
I thought the ability for easy compression adjustment was a big deal but in reality, it wasn't...
I thought I would be adjusting my fork compression more than I actually am. Perhaps on a track bike it would be true but on my street FJ once I have it set, I've left it alone. It did take me 3 tries with FZR forks to get the shim stacks exactly where I wanted (you gotta take the forks apart ) but once done, all was well.
The FZR USD swap is plug and play by comparison to the YZF.
Get the entire FZR front end, rim, axle, spacer, speedo mech drive, forks, upper triple lower triple w/ stem and fender. It will make things easier.
Quote from: Pat Conlon on September 23, 2025, 02:48:58 PMBoth the FZR1000 and YZF750 front ends use a mechanical speedo drive that the FJ cable plugs into.
I switched from the FZR1000 USD's over to my current YZF750 USD's and here's what I've learned.
Stay away from the YZF750 front end, it takes too much work. You have to use the YZF lower triple, punch out the short fat YZF stem (too short too fat for the FJ steering neck) then weld up increasing the diameter of the skinner FJ steering stem to fit in the big hole in the YZF lower, then press the modified FJ stem into the YZF lower clamp. It's very involved for little benefit . .
The only thing you gain with the YZF750 USD forks vs the FZR USD's are that the YZF forks have external compression adjusters...the FZR forks do not. You set compression on the FZR forks via a shim stack inside the forks. Both forks have external rebound and preload adjusters.
I thought the ability for easy compression adjustment was a big deal but in reality, it wasn't...
I thought I would be adjusting my fork compression more than I actually am. Perhaps on a track bike it would be true but on my street FJ once I have it set, I've left it alone. It did take me 3 tries with FZR forks to get the shim stacks exactly where I wanted (you gotta take the forks apart ) but once done, all was well.
The FZR USD swap is plug and play by comparison to the YZF.
Get the entire FZR front end, rim, axle, spacer, speedo mech drive, forks, upper triple lower triple w/ stem and fender. It will make things easier.
This is exactly what I was looking for Pat. Modification for the stem, etc.. this is not an issue for me. I was wondering only if that make sense to do more work for compression adjustability and looks like for street use not so much.
Thanks Pat
Happy to help Mario
FYI if you go with FZR1000 front end...the stock FZR springs (.77kg/mm) are too light for our heavier FJ's.
As we know, the springs control the suspension but the valves control the springs so with the heavier springs you should change the valves (unless you like boing boing boing pogo stick fork action)
After 2 variations, here's my final spec:
Oil level: 110mm
Sag: 35mm
Spring: 34.7 x 340 .95kg/mm (you could go with heavier 1.0kg/mm springs)
Race Tech Compression valve: FMGV S2045
Compression bleed #55 drill (.052in.)
Compression stack C38
Rebound stack R20
Rebound needle base setting 1 turn out
Oil 125/150 Golden Spectro cartridge oil
This should save you some work.
Cheers
Pat
Quote from: Pat Conlon on September 24, 2025, 03:24:17 PMHappy to help Mario
FYI if you go with FZR1000 front end...the stock FZR springs (.77kg/mm) are too light for our heavier FJ's.
As we know, the springs control the suspension but the valves control the springs so with the heavier springs you should change the valves (unless you like boing boing boing pogo stick fork action)
After 2 variations, here's my final spec:
Oil level: 110mm
Sag: 35mm
Spring: 34.7 x 340 .95kg/mm (you could go with heavier 1.0kg/mm springs)
Race Tech Compression valve: FMGV S2045
Compression bleed #55 drill (.052in.)
Compression stack C38
Rebound stack R20
Rebound needle base setting 1 turn out
Oil 125/150 Golden Spectro cartridge oil
This should save you some work.
Cheers
Pat
Pat, you are the man!
Will need to organize for you nice case of Moosehead Canadian LAGER :drinks:
Thanks Mario, I'll pass on the beer but if we ever meet, a cuppa joe will work.
Let us know how your mods turn out.
Pat
Quote from: Pat Conlon on September 24, 2025, 05:22:04 PMThanks Mario, I'll pass on the beer but if we ever meet, a cuppa joe will work.
Let us know how your mods turn out.
Pat
You got it Pat. :morning1:
Thank you