honda f4i rear shock

[Dads_FJ]

Okay, done with the Honda f4i shock mod. Wow - I don't think the bike ever rode this nice.

1).  The top of the Honda shock needs to be drilled to the size of the FJ bolt, no biggie but keep it straight.  Because the shock is narrower, two 10mm spacers need to take up the space.  Image 1.

2).  The bottom of the honda shock uses a 17mm ID X 24mm OD needle bearing with 2 seals.  Press out the bearing and seals and replace them with two 18mm x 24mm x 12mm bearings and two 18mm x 24mm x 4mm seals.  images 2-4

Image 1


Image 2


image 3


image 4



Before and after:



Pros:
•   Cheap – Shock was $50 to my door plus $36 for bearings and seals.
•   Honda shock is rebuildable and fully adjustable, and did I say cheap?
•   Can go back to stock shock or better aftermarket, no modification to the FJ chassis was made.
•   Easier to get on center stand, WAY easier.
•   Ride height was increased.

Cons:
•   Now I can tell my front end need attention.
•   Rear wheel touches the ground when on center stand.
•   Preload is a bitch to adjust.

[Dan Filetti]

Dad's

This is really nice work.  Kudos for the documentation.  This sure seems like a doable way to upgrade your FJ rear suspension to a more modern shock.  I'm wondering about what you did to compensate for the 150+ lb weight difference and requisite shock setup between the doner F4i and the FJ.

Only other issue I can see is there does not seem to be a ride height adjustment, but hell, for $86 it sure seems like an amazing way to make a decent upgrade.

Thanks for sharing,

Dan   

[Dads_FJ]

Dad's

This is really nice work.  Kudos for the documentation.  This sure seems like a doable way to upgrade your FJ rear suspension to a more modern shock.  I'm wondering about what you did to compensate for the 150+ lb weight difference and requisite shock setup between the doner F4i and the FJ.

Only other issue I can see is there does not seem to be a ride height adjustment, but hell, for $86 it sure seems like an amazing way to make a decent upgrade.

Thanks for sharing,

Dan   

And thanks for the compliment!  This set up may not match up to a more expensive shock, but I can say is that there was a dramatic improvement just bolting it on.  However I'll be the first to admit that my riding skills wouldn't match others on the list.  Also my testing grounds are pretty straight and flat, so I'm not really pushing the limits of me and/or the bike.  I think the old shock was so bad a straight rod would have been better, but it's just not in my budget and I cannot afford the correct aftermarket shock for my bike.

By 'ride height adjustment' do you mean pre-load?  If so it's there, but a bugger to adjust.  I guess by fully adjustable I meant preload, and compression & rebound damping, but not ride height, sorry for the confusion.

[ian.z9]

This was the mod I was looking for as my FJ looked a little droopy at the rear after fitting the gsxr wheel.I couldn't find a F4I shock
so I used an F3.Looked about the same but the preload is easy to adjust with the right C spanner.Centrestand is abit dodgy as the wheel is on the ground but I can weld a riser on the foot of the stand to get the rear wheel up.Rear chain is closer to the exhaust and was touching it until I adjusted the chain tighter,not too tight so check it when you are sitting on the bike.Could be a good excuse to fit my 4into1 race pipe as there would be no chain touching problems then (maybe some from the neighbours.I leave at 6.15am)Shock action is ok but I'm not that fussy as the roads here are straight and after my zed anything feels stable.I just got a bush made for the bottom of the shock like the original yam shock.The needle bearings look better so I should upgrade it I think.A Penske has to be better but for 50euros this will do for me.

[WhiteBeard]

Clean looking ride! 

[fj11.5]

yep, huge improvement in handling, , , the lower bearings are a good idea, may have to do that too, couldnt find them when i bought mine, so the bush had to do,,,, 

[Arnie]

Dan Filetti said, " I'm wondering about what you did to compensate for the 150+ lb weight difference and requisite shock setup between the doner F4i and the FJ."

I would suggest that the suspension lever ratios of the F4i and the FJ are different enough that the stock F4i spring works very well on the FJ.  Rough calculation (I don't have a spring tester any more) shows the F4i spring at about 1000 lbs/in.  It is also possible that the F4i is sprung very hard so it is ready for track work.

If they both used their shock and springs in a direct manner without linkage or rockers like the Aprilia Shiver or Kawasaki Versys then the weight difference would be more of a concern.

Arnie

[axiom-r]

The skinnier R1 shock I started with was only 500lbs/in and was far too soft for the FJ.  If the F4i is in fact a 1000lb/in spring you should be in decent shape.  I ended up with a 1400 lb spring on my Penske but I definitely messed with the linkage causing it to require a stiffer spring....  I see from the pic of the F4i shock it has no ride height adjustment. Perhaps you can lower it slightly by changing the dog-bones to a different length. Ideal ride height would give you a half inch of clearance under the back wheel when on the center stand.  I know others have been able to deal with this issue in this way.

Nice work!

tim

[ian.z9]

You can see here that its easy to adjust with a C-spanner.The older cbr shock has the preload ring higher up the shock.Not that adjusting it makes that much differance.Haven't had a passenger on yet.Bouncing the rear of the bike up and down and comparing it to my workmates S1000RRRRRR beemer shows the shock to be underdamped but its not costing me 15grand so I'll put up with it.It does feel ok when riding but it should be better when I replace the rear tyre soon. 

[FJmonkey]

I don't think the 84/85 has dog bones. The 86/87 don't have them either.

[baldy3853]

So Mark tell me why we can't see your feet in
your profile picture...........

[fj11.5]

I don't think the 84/85 has dog bones. The 86/87 don't have them either.

correct , no doggy bones to chew in the 84 models

[axiom-r]

I don't think the 84/85 has dog bones. The 86/87 don't have them either.

ahhhh  that's right.  My mistake!

[yamaha fj rider]

  That is a super mod. It has to work better than the stock shock and is very reasonably priced. Good work on this one thank's for the R & D and pictures!

Kurt

[FJmonkey]

I don't think the 84/85 has dog bones. The 86/87 don't have them either.

In my best Jedi mind control voice "There is nothing to look at, these are not the boots you are looking for".....