F4i Details?

[fintip]

I've done lots of searching, but I can't seem to find Arnie's original post on the F4i rear shock install. (Or any other comprehensive walk-through.)

I came into some money recently, and thought I might splurge on an F4i and then Randy's front fork mods here soon, wanted to start doing my research (and add the info to fjowners.wikidot.com/rear-shock and fjowners.wikidot.com/forks). To have decent suspension would just make my day... Not that I'll ever truly be satisfied until I have Randy's shock, but it will be a while until I make that kind of money.

Of course, this is preliminary. I'm finally going to fix up FJ #2 that I bought here this week and get that riding for a friend (hopefully just a gasket, the clutch slave, and an oil change, but we'll see), and I'm going to steal some of the nicer parts off of it, including a kerker 4-into-1 that sounds AWESOME. But I need to make an organized prioritized upgrade wishlist and decide where the money will go. Total suspension overhaul for about $300-$400 sounds like a pretty good investment, though... Already have parts for a clutch rebuild, will be doing that soon too!

(I sure wish the transmission rebuild wasn't such an expensive, labor intensive job, though. That's pretty high on my wish list, but I wonder if that will ever get done.)

[Dads_FJ]

Here's the write-up I did on my '84, later models differ though.  http://www.fjowners.com/index.php?topic=6549.15

[fintip]

Anyone know how different the 86/87 will be? I know I also don't have dogbones, but what are the differences between the first gen and second gen?

Also, stupid small question: on the stock oil filter housing, reinstalling... Does the spring go on the side of the filter closer to the bike or closer to the outside? I feel pretty confident that the spring goes on the outside, but I'm not 100%, and I've had it sitting out for so long on FJ #2 that I'm really not sure and don't feel like pulling mine off to check.

[jscgdunn]

84 and 86 are the so far as this goes jeff

[fintip]

No difference in the mount points?

[FJmonkey]

Also, stupid small question: on the stock oil filter housing, reinstalling... Does the spring go on the side of the filter closer to the bike or closer to the outside? I feel pretty confident that the spring goes on the outside, but I'm not 100%, and I've had it sitting out for so long on FJ #2 that I'm really not sure and don't feel like pulling mine off to check.

You need the spring to push the filter against the case, so your guess is correct.

[fintip]

Thanks Mark. 

[fintip]

Meh, I had forgotten how expensive things were. The front fork valves are over $200 all by themselves, plus new springs at $140... *sigh*

As for the F4i, I've never dealt with a rear shock before, know only what I've read here. How much would it cost to replace the spring on it (higher weight), and/or revalve it?

[jscgdunn]

The 84 through 87 shock mounting is the same.

In terms of the spring, you may want to use your old FJ spring.  I have not done it, but here is a pic of a 92 fj spring on an 2007 R1 shock.



This is a much stiffer spring than the Honda F4I spring.

Jeff

[rktmanfj]

What's the rating on the OEM FJ spring?   

[jscgdunn]

I will let George confirm, as I cannot find his email in the strange new yahoo email setup, but I recall it is 1250-1300 pounds (3XW).

Jeff

[FJmonkey]

Skymasteres (AKA Mike) also has an F4i shock he had revalved and resprung. http://www.fjowners.com/index.php?topic=7691.msg110701#msg110701

[jscgdunn]

Sorry that's 13.5 KG/MM or 754 pounds.

Springs are rated in pounds/inch in the U.S., and Newtons/millimeter elsewhere. I have not seen kilograms/millimeter before, but the conversion will be easy enough.

1 pound = 0.45359237 kilogram
1 inch = 25.4 millimeter
0.45359237/25.4 = 0.0178579673228346

The conversion factor is 0.0178579673228346

So, to convert lb/in to kg/mm you multiply by 0.0179 and to convert kg/mm to lb/in you divide by 0.0179

[movenon]

I just put a 1990 FJ spring on a R6 shock using a Race Tech collar.  I had a 950 lb Eibach spring installed with a Race tech bottom collar and a spacer (aftermarket springs are shorter by about 1/2 inch).  That was a little light for me.  Information on spring rates from Yamaha is a little untrustworthy IMO.

Here is information from Yamaha Service Guides but I don't trust that information:

Reference Yamaha Service Guides; Rear shock spring rates.
FJ 1200 S/SC   17 kg/mm     (952 lb)
FJ 1200 W/WC  20 kg/mm    (1120 LB)
FJ 1200 B/BC    13.5 kg/mm  (756 lb)  

I can tell you as a fact with a 950 lb spring (calibrated) that I weigh 225 lb and with a tank bag, full tank of fuel and rear rack that the static measurement was OK,  the sag measurement was close but at max preload.  I want my sag measurement on a scale of 1(lightest) to 10 steps of adjustment at the shock to be step 3 or 4.

I estimate that I probably need a 1050 lb spring,  I just have a 1990 FJ spring on hand and am curious how it measures out on the bike. The 1990 FJ spring is probably 1050-1100 lbs..

Here is some information on Penske shock spring rates. I am finding it to be pretty close.

Data in lbs/inch.
Divide by 56 to convert to kg/mm

                         Spring     120-160#      160-190#            190-225#          225-260#
                         Length    with gear       with gear            with gear          with gear
FJ 1100   85-87....... 6..........850...............900.....................950..................1000
FJ 1200   88-89........6..........900...............950....................1000..................1050
FJ 1200   1990.........6..........850...............900......................950..................1000
FJ 1200   91-93........5..........900...............950....................1000..................1050

After that you need to figure out if the shock can handle the rebound and compression if you go to far over the stock spring rate.  Some shocks are easier than others to set up.

Hope it helps.
George

[fintip]

I have a lot of this information on the stock shock over on fjowners.wikidot.com/rear-shock, for those that are wondering for reference. I just don't know what to do with those numbers. (Though you have all added a bunch of good info I probably don't have there, would love it if someone would go add it for themselves!)

I had read about skymasteres' f4i experience, and it swayed me to try it--however, he gives little information about price or procedure, just says that he paid someone to customize it for his FJ. (Would love it if he would weigh in on this!)

As I said, I've never really done anything with a rear shock--never even messed with the adjustments, though I've read about the ideas behind them and watched videos on doing so properly. All that said, talking through the process like I'm completely ignorant would definitely be helpful, this discussion is super technical so far! (Which is great, just, really hard to process for me since I've never done it before).