FJ1200 Fork Rebuild Advice

[ajacstern]

Hi Guys,

I am rebuilding my forks over the winter and found different parts in the forks than is specified in the manual when I took them apart. I was also met by a too small amount of shiny, metal-flaked fork oil upon disassembly, but all the metal that came out is just weight savings really. I included a picture of the manual I am referencing in the album at the bottom. I do not see the fork spring seat (number 6), the wave washer (11), or the lower regular washer (12). Additionally, the spring has several close coils at the top and looser spaced coils at the end, I am wondering if this is the stock spring or a progressive aftermarket spring? That might explain why there is no fork seat. Alternatively, this is the FJ1100 and FJ1200 manual from Yamaha and I have an '87 FJ1200, so the missing parts might only be present in the earlier 1100 models.

Hopefully this fluid change with new ATF will make the forks somewhere near usable. They are still way undersprung and nearly bottom out with just the bike's weight on them, but I am not sure if I want to do a fork conversion or springs and emulators yet. Would like to get a 17" front wheel and I haven't seen any 88+ FJ fork lowers so I might be going the fork conversion route.

Album:





Cheers.

[Mark Olson]

greetings, I have an 86 and spent a lot of time messing with my forks before I put 90 lowers on it.

Answers to your questions:
That is a stock fork spring not progressive , just how they made them.
As for 11&12 that is part of the Anti-Dive and I would suggest leaving out 11,12,13,14 ... this will disable the anti dive and stop your FJ from standing up in corners while braking.
you don't need block off plates if you remove the top hat looking #14. just bolt antidive back on.
do you have the #5? some do others don't .....Anyway , you can put a piece of 3/4" PVC and cut to length to increase your ride height usually 3" of pipe ... adjust length to get your sag #'s.
(so toss #5 and substitute the PVC or metal tube)

change the bushings #10&20 and the fork seals and dust seals #15&18.

If you are an aggressive rider use ford type-F= 20w.   Measure carefully how much oil you put in ... Makes a big difference.

Yes this does work and I rode around with this setup for years.

Enjoy the Ride.

[FJ_Hooligan]

Those are the OEM springs.  They are a dual-rate spring.  When the close coils bind up on each other the spring becomes a stiffer rate.  Unfortunately, by the time that happens, your fork is almost out of travel.

One solution is to cut off the close wound coils and increase the spacer length.  This will give you a better spring rate to work with.

The better solution is RPM straight rate springs and fork valves.

[fj1289]

...
As for 11&12 that is part of the Anti-Dive and I would suggest leaving out 11,12,13,14 ... this will disable the anti dive and stop your FJ from standing up in corners while braking.
you don't need block off plates if you remove the top hat looking #14. just bolt antidive back on.
...

Thanks Mark - first time i remember reading that bit to internally disable the anti dive but still keep the units in place

[ajacstern]

Ok, good to know that a few of those missing parts are antidive related. I didn't take it off because I don't have spare o-rings / gaskets for it and don't use it anyway (disconnected the brake lines), so maybe that is where those parts are (or maybe the previous owner disabled it, but I think I am the first one in these forks). Also I have no number 5, no spacer in the forks at all. I do have new bushings and seals that I will be using.

I was looking at some posts about cutting the springs for a harder spring rate and I would like to do that, but I can find no schedule 80 PVC anywhere near me. Is schedule 40 sufficient? I definitely don't want the spacer breaking suddenly. I assume I would also want to put a washer under the PVC to work as a spring seat, given I am also missing that part? The RPM fork upgrades might be coming in the future, USD forks are pretty sexy though.

Thanks for the advice.

[Mark Olson]

40 pvc is ok to use.  Also metal emt . With washer.
Yes you can cut spring . 

[ajacstern]

I ended up ordering 304L stainless steel spacers from McMaster-Carr because I heard some issues with PVC being too brittle and shattering after repeated impacts. Unfortunately, I realized after ordering unusually expensive steel that the ends of the spring would have to be turned perfectly flat or else the spring would bind against the inside of the fork tubes. I was just going to grind it down flat enough to put a washer on, but if it is not a fairly accurate flat surface then the spring will experience sideways forces and push itself against the inner walls causing damage and binding. I can't think of anyway to get it anywhere near as flat as it is currently. I will call a machine shop and ask what they would charge to turn it flat, but I imagine it will cost much more than just buying new springs. Has anyone who has cut their springs found a way around this?

[Pat Conlon]

Nope, I threw my weak sauce stock springs away....far away.
If you just want to do the fork springs alone, get progressive springs. Money well spent.
If you plan on doing the Race Tech cartridge emulators or RPM valves, get straight rate springs.

My second mod to my '84 was progressive springs (after SS brake lines)

[fj1289]

Pretty sure the spring is always rubbing against the sides of the fork tube. 

It you are really concerned - weld a tube to the washer so it fits inside the spring to keep it centered on the washer - or used a stepped bushing to do the same. 

Or just flip the spring and place the cut side down.

[ribbert]

Not weighing into any other aspect of this discussion but I would most definitely not be cutting springs, they would have to be machined flat and that's just not worth it, springs aren't that expensive. Think about the profile of a cut spring and picture how all the load would sit on the end of it . Cars are different, the top and bottom plates are shaped for a cut spring.

As for the plastic spacer, there is a member whose bike has been subjected to more extreme abuse over more miles than I would think any other FJ here, it's had plastic spacers for years. I can understand why it appears to be under spec for the job but it's not, there are hundreds of FJ's here using them.

Noel

[Bones]

When I bought Randy's valves and racetec springs it came with a length of pvc pipe that you cut to size. It was thick walled and looked plenty strong enough, no problems so far after a few years use.

[ajacstern]

The potential issue with PVC isn't that it can't handle the weight, it is that it is too brittle to take a lot of sudden impacts (E.G. slamming the front down after a wheelie). I don't do a lot of wheelies with the FJ, definitely not the right bike for it, but I have seen some people in the dirt segment say they break or chip off over time in that kind of environment. They are probably fine 99.9% of the time and are unlikely to have an issue, especially in this application, but I bought metal anyway.

Yes, machining the ends flat is making it looks like this is a waste of time considering fork springs really aren't that expensive, I was just hoping to do a quick edit while I already have the forks apart. I have considered cutting the end of the spacer to fit the curvature of the fork spring end, but I have no idea how precise it needs to be and if I will be able to get close enough with my eye and emory cloth. Welding an internal tube like you mention fj1289 sounds like a smart way to go, but I don't have a welder either unfortunately. Hoping their will maybe be a generous machine shop owner who will form the ends flat for less than the $50 it would cost to make this mod economically sensible, but I highly doubt it.

I am undecided if I want to go for a FZR1000 (or any USD) front end swap or RPM valves and springs yet, but I can't do either of those at current time. I don't want to buy progressive springs now and then another set of straight rate springs / another front end in a year or two, so I was hoping for a short term fix. Would straight rate springs without the RPM valving work well, or is it preferable to go progressive for damper rod forks?

[Mark Olson]

I am undecided if I want to go for a FZR1000 (or any USD) front end swap or RPM valves and springs yet, but I can't do either of those at current time. I don't want to buy progressive springs now and then another set of straight rate springs / another front end in a year or two, so I was hoping for a short term fix. Would straight rate springs without the RPM valving work well, or is it preferable to go progressive for damper rod forks?

That is up to you. The short term fix is to just put your stock springs back in with spacers/washers. Many have used pvc with no problems, I use metal tubing.

Depending on your riding style, If you are planning on keeping the FJ for a while.
you really need to change your lower fork legs to 89+ so you can change front brake calipers to blue dots and run 17" 3.5 wide front wheel.
Then you will also need a fork brace , FJR brake and clutch masters.
parts are getting scarce so remember you only need lowers and can use your upper fork legs in the 89+lower fork legs. (many recyclers have these not listed because the uppers are bent.)
call around.

once you start down that path it will become clear to just do the front end swap to USD's.

Remember " chicks dig the USD forks"

[RPM - Robert]

Race tech exclusively sends PVC with all of their spring kits. They stopped using metal 5-6 years ago. I would say one of the biggest motorcycle spring manufacturers in the world probably knows the deal.

[FJ_Hooligan]

Not sure I would use Schedule 20 PVC, but Schedule 40 has been working on mine for 30+ years.

You could heat the end coil with a torch and let it sag to the next coil.  It's not like we're talking piston ring gap critical