GSXR1100 (1991/1992) Fork upgrade

[fj11.5]

I've been using an f4i shock on my 1100 with no issues of a soft spring,  preload at 3 rebound and compression both about quarter turn from lowest set, but I'm maximum 75kg depending on the week  , , randy at rpm is working on having his shocks out soooon,  if your going to buy new,  these are made especially for the fj,s

[Arnie]

Jason,

I don't believe anyone said the F4i shock was ideal to use in the FJ.
However, it is not a $600-1000 spend item either.
The spring on mine could stand to be a bit stiffer than it is, but as is it is MUCH, MUCH better than the OEM FJ spring and the damping of the shock is better and more adjustable than the OEM FJ shock ever was.

The '89+ FJs were sporTOURING bikes, and were given very soft springs.
The Honda F4i 600s were a "proddie racer" that was street legal, and given (almost) race suspension.  As such, they were much stiffer, relatively, than the FJs so just looking at the bike weight does not tell a full story.
I'm certain that a purpose built shock from Ohlins, WP, Penske, Bitubo, Sachs, RPM, and other manufacturers would be 'better' than the kludge of swapping in a F4i shock.  In fact, you will almost certainly be able to find another "take-off" shock from some other bike that will work better in the FJ. 
But, YOU've got to buy and try all those other bike shocks and then do the swap and report back here.
I've swapped springs and had springs made for the OEM shock and changed preload spacers.  I've also bought and tried a GSXR1100 shock before buying and trying this Honda F4i shock.

Please let us know when you come up with either a cheaper or better choice.

Arnie

[FJNovaScotia]

Thanks Arnie,

Will do!

Jason

[movenon]

I got the 1990 FJ up and running today after a winter of mods including a F4i shock. On a short "safety of flight" run, I have to say the shock works great for me. Intially it seems is a lot better than the old FJ shock. I will admit that I did not push it hard or run it over 50 - 70 mph. I was looking for big issues not tuning the suspension. Also I wasn't wearing my helmet or gear, I was listening and looking for problems.

For the lack of terms it seemed to track better, take the road irregularities better. I also ran it down an "Idaho freeway / cow trail " unimproved dirt road with 4 to 6 inch deep "chuck holes" about 1 1/2 to 2 feet in diameter and it seemed to work right through them with out pitching , banging or lost of control. 
It felt a hell of a lot better than my stock rear shock and my current front end......... That's another issue on the horizon. 

Tomorrow I will take it on more of an extensive run and will play with the suspension settings.

As far as the F4i shock.  I weigh 216 lb (97.7 kg), the bike has a rear rack with an empty top box and tank bag with approximately 1/2 tank of non alcohol laced fuel  ... Dogbones are at present are about 125 mm C to C and the rear end sits about 1 1/2 inches (38.1mm) taller. On the center stand with a 2 X 8 (1 1/2 inch thick) under it the rear wheel the tire clears the floor about 1/4 inch. I have the preload set on the 4th or 5th position.

That's all I have at present. For the 75.00 dollars total I have in the shock I am pleased with it at least in a touring mode. With more seat time I will be able to evaluate the conversion more but I am not a track or street racer.  I had the opportunity to ride a full up track only bike once (I used it to take the MSF course as my bike was down for repairs) and suspension settings in that range are a different animal, for long distance street riding I don't think I would enjoy it.
George

[giantkiller]

I'm 280lbs. So I needed a stiffer spring. Would have liked to go heavier than 900lbs on the spring. But that seems to be the limit of what the honda guys think the stock rebound can handle without a revalve. I'm going to have $115 into the spring(including bushes and motorcycle spring compression tools) So $170 total into the shock.
That will be a sh.tload better than an fj shock.

[movenon]

Yes, you have to consider that the dampers have limits and given enough spring it will over whelm it.

I just took some measurements on my bike with the F4i shock.  Got a helper to give me a hand and measure. 
static (unloaded pulling up on the bike with the rear wheels of the ground) 8mm
bike vertical with no rider my measuring point was 480mm
bike with me on it in riding position                     440mm
sag measurement 40mm plus 8mm = 48mm with spring on the number 5 slot/ramp.
Rider weight 216 1/2 tank fuel, rear rack and top box.

I am not suspension guru so please forgive any errors and correct me. Just a guy in the garage..
George

[movenon]

In researching information on another problem I stumbled into a 1991 Factory FJ manual (its online here in the "files section) and they gave the FJ rear shock spec's as:

Shock travel..........................48mm (1.89in)
Spring free length...................181mm (7.13 in)
<limit>..................................174mm (6.85 in)
Fitting length.........................164mm (6.46 in)
Spring Rate...........................132 N/m (13.5 kg/mm, 756 lb/in.... model K1
stroke..................................Zero 48 mm (Zero 1.89in)
Optional Spring......................No
Enclosed Gas Pressure............1200 kPa (12 kg/cm2, 171 psi)

Note the spring rate, 756 lb/in. But there is a lot more to it than rate, length, rate at which it gets to max etc. But it interesting that it isn't far off the f4i shock.
Just information to throw into the pot.
George

[fintip]

Shameless plug/example...

I saw that information, and thought it'd be a nice thing to have on reference. I went ahead and typed in

fjowners.wikidot.com/rear-shock

clicked 'create page'

signed in (you will have to register the first time)

and added some basic information and then the stats listed.

It's small and incomplete... But hopefully you guys will add info to it and links to other things when you notice it now or in the future.

Slowly but surely...