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General Category => Maintenance => Topic started by: ajacstern on March 22, 2021, 08:06:53 PM



Title: Fork Bushings
Post by: ajacstern on March 22, 2021, 08:06:53 PM
Hi all,

The FJ1200 forks I mentioned previously are still apart as I have had issues finding the right slides / bushings. I bought a pair off K-tech, they didn't fit all. Couldn't even get the outer tube on they were so large. Ordered a second set for Race-tech, same problem they are also too large. I tried sanding them down but it's taken 3 hours and I'm only 90% of the way their on one bushing (it was the first nice day outside so I didn't mind sitting out on the porch sanding). Couldn't get a flap wheel or a rotary tool to work. I have no plans to spend another 3 hours doing the next bushing, so I am going to buy a brake hone and see if I can get that to work.

The potential issue is the sanding goes right through the inner copper layer on the bushing. The part of the bushing that the fork slides against is the outside with a Teflon coating so I wouldn't think removing the copper would cause a problem. I can think that it might rust, but it should be bathed in oil so I doubt it. Can anyone think of a reason I shouldn't sand them down? Will definitely buy RPM bushings and seals next time (unless I swap to USD forks :)), though the issue might be that the forks are out of round.

Cheers.


Title: Re: Fork Bushings
Post by: FJmonkey on March 22, 2021, 10:10:03 PM
How do you know if you are removing an equal amount all around? If not you will end up with a tight spot that you might not be able to feel. That spot then becomes a location of accelerated wear. Not worth it in my opinion.

Removing the copper from the back side is not an issue. The bearing is copper/brass electric deposit so all surfaces get coated. Then the PTFE is applied over the copper/brass layer.


Title: Re: Fork Bushings
Post by: Pat Conlon on March 22, 2021, 10:24:40 PM
Something’s wrong. Stop sanding.
I have never heard of FJ fork bushings needed to be sanded.
Measure the new unsanded bushing. Call Robert at RPM and have him measure their bushings.
Start from there.

Don’t know about K-Tec but I have always had good results with ordering fork bushings from Race-Tech.


Title: Re: Fork Bushings
Post by: racerrad8 on March 22, 2021, 10:36:44 PM
As Pat mentioned, measure what you have as replacements. Compare them to the bushings you removed to determine if there is a difference.

That should be your first step. From there it's time to call your suppliers and inquire why they are not fitting.

If you already called them, what did the two suppliers you purchased the bushings from offer as an explanation?

Randy - RPM



Title: Re: Fork Bushings
Post by: ajacstern on March 23, 2021, 12:47:31 PM
I was thinking the copper was probably deposited on the back by an electrolytic process, thanks for confirming. I know they are still round because I was really really careful when sanding haha. No, the one done by hand may be slightly out of round but the brake cylinder hone I now have should produce fairly round bushings.

I called Race-Tech, they said manufacturing tolerances and it might break in. I could barely move the fork tubes between each other so no way it was breaking in easily or without significant wear to the bushing. The bushings from both manufacturers measure in about the same, 1.1mm thick whereas the old bushings are 1.0mm thick with a few 0.96mm spots. The inner diameter on the other bushings is slightly smaller, 39.70 as opposed to 39.9 on the original.

I am considering putting the used bushings back on, they probably have 22k miles on them but there is still some plastic on one, the other one was destroyed when pulling the fork apart (rust seizure). At least one of the bushings will have to be milled out as I would like to get the forks together in the next couple days (it is supposed to get cold again next week for whatever reason). An accelerated wear spot is probably better than very worn bushings?

Thanks for the advice.


Title: Re: Fork Bushings
Post by: Old Rider on March 23, 2021, 02:36:54 PM
I think you got wrong slide  it must be for the later type fj1200 or something  i looked at some partnumbers and found something strange.
That is that the fj1100 and fj1200 with antidive has same bushings the later type forks without antidive has another partnumber ,but all are superseeded
with same partnumber !. Maybe that means that it is not possible to find the older bushings that andtidive forks uses. Try to contact yamaha dealer and ask.
here are some partnumbers i found.

1985 fj1100
product number: 36Y2312510
supersession: 3JD23125L

1984 fj1100
product number: 36Y2312510
supersession: 3JD23125L

1986 1200
product number: 36Y2312510
supersession: 3JD23125L

1992 1200
product number: 3LC2312500
supersession: 3JD23125L


Title: Re: Fork Bushings
Post by: Alf on March 23, 2021, 03:16:55 PM
All FJ models use the same bushes. In fact, the lower ones are not specified at the 91 on last model parts manual, but I order previous one without problems
And TRX 850s use the same ones

I know a case of late from an Spanish owner where the bushings bought on eBay looked the same but were impossible to fit


Title: Re: Fork Bushings
Post by: andyoutandabout on March 23, 2021, 08:25:59 PM
I've said it before and I'll say it again.
Forks - miserable job - let Randy do it.
The reasons are many fold.
One, I wouldn't know when a bushing was actually worn out in the first place.
Two, installation of things like bushings, bearings and seals is just a black art that I wasn't gifted with and would doubtless wreck new part during ham-fisted installation.
Three, 'the eye' mentioned above also notices things like it might not be the bushings worn out , but the actual fork tubes.
Anyway, best of luck going it alone, you might have the knack after all.


Title: Re: Fork Bushings
Post by: Old Rider on March 24, 2021, 02:34:04 AM
Forget all about my post above  :blush: I had a look at RPM and they have it all sorted out as usual :
https://www.rpmracingca.com/proddetail.asp?prod=M%2FC%3AFJ41ForkR%2FBKit (https://www.rpmracingca.com/proddetail.asp?prod=M%2FC%3AFJ41ForkR%2FBKit)

They even got a 27mm  handy fork tool that i did not know about  :good:
https://www.rpmracingca.com/proddetail.asp?prod=27mmForkHolder (https://www.rpmracingca.com/proddetail.asp?prod=27mmForkHolder)


Title: Re: Fork Bushings
Post by: Alf on March 24, 2021, 02:45:51 AM
Randy kit quality is superb, I don't remember when I rebuilt my 3CV forks... well, years ago... 100.000 km?... I know it is a lot of time because with the same settings It feels softer than my 1TX rebuilt fork from last year (same 3CV fork fitted), so maybe time to replace bushings...


Title: Re: Fork Bushings
Post by: ajacstern on March 24, 2021, 11:13:25 AM
Yes, very odd as I couldn't find a Yamaha part number that seemed like the right part. Don't know what's up with the bushings but I am going to run with what I have, maybe get RPM's rebuild kit if I am not going to do a fork swap. This setup will hopefully last at least this year. I have done forks a few times cause you have to rebuild them every year with dirt bikes, you can tell the bushings are worn when the plastic coating is worn through to metal.

When I assembled the forks, I measured the travel without the main spring in it to be 5.3". This is lower than Yamaha's 5.9" specification. There is a spring on the damper rod that might account for another 0.6" of travel, too challenging to compress it by hand and measure at the same time. Does this sound right? I keep worrying that the bottoming cone has fallen off the end of the damper rod but it shouldn't have.

Thanks!


Title: Re: Fork Bushings
Post by: FJ1200W on March 24, 2021, 11:58:56 AM
Randy kit quality is superb, I don't remember when I rebuilt my 3CV forks... well, years ago... 100.000 km?... I know it is a lot of time because with the same settings It feels softer than my 1TX rebuilt fork from last year (same 3CV fork fitted), so maybe time to replace bushings...


You're right - Randy's kit is awesome.

But, alas, it does not install itself...... I need motivating!


Title: Re: Fork Bushings
Post by: ajacstern on March 24, 2021, 09:05:19 PM
The other fork travelled the same so I think that is correct. Last snag is I wrote down the forks' height in the triple trees but cannot for the life of me find where I wrote it down. Does anyone know how high in the triple tree FJ forks are supposed to be?

:Facepalm:


Title: Re: Fork Bushings
Post by: FJmonkey on March 24, 2021, 09:36:09 PM
If you are still using the stock clip on bars then that high. If you did not clean the forks back to a polished state then the clamp marks work as well to put them back.


Title: Re: Fork Bushings
Post by: chiz on March 27, 2021, 07:14:49 AM
I've said it before and I'll say it again.
Forks - miserable job - let Randy do it.
The reasons are many fold.
One, I wouldn't know when a bushing was actually worn out in the first place.
Two, installation of things like bushings, bearings and seals is just a black art that I wasn't gifted with and would doubtless wreck new part during ham-fisted installation.
Three, 'the eye' mentioned above also notices things like it might not be the bushings worn out , but the actual fork tubes.
Anyway, best of luck going it alone, you might have the knack after all.

Wat.... I would rather do FJ forks all week than a valve shim job or swing arm etcetc. pulled forks apart on triumphs bsa' can am's  xs's  kawa's.. I find it simple and only had to make a holding tool for the can am. The XS 850 is a pain because of the sillly circular clip that holds the whole team in the tube.

   Chiz


Title: Re: Fork Bushings
Post by: krusty on April 06, 2021, 08:30:14 PM
Only slightly OT. I'm just about to reinstall my FJ12 forks after replacing seals. Should I lightly linnish them?


Title: Re: Fork Bushings
Post by: fj1289 on April 07, 2021, 08:24:29 PM
Only slightly OT. I'm just about to reinstall my FJ12 forks after replacing seals. Should I lightly linnish them?

The bushings or the fork tubes?  I would the fork tubes - may find a tiny nick with a sharp edge that would cut the new seals otherwise.


Title: Re: Fork Bushings
Post by: krusty on April 08, 2021, 04:39:38 AM
Only slightly OT. I'm just about to reinstall my FJ12 forks after replacing seals. Should I lightly linnish them?

The bushings or the fork tubes?  I would the fork tubes - may find a tiny nick with a sharp edge that would cut the new seals otherwise.
Thanks. The tubes. The look a bit too smooth and "polished".


Title: Re: Fork Bushings
Post by: fj1289 on April 08, 2021, 04:06:29 PM
Uh, I think we’re missing each other - I was referring to the hard chromed inner tubes vice the aluminum “sliders”!

Although I really like to look of polished fork sliders, my next set will get painted black. 


Title: Re: Fork Bushings
Post by: krusty on April 08, 2021, 05:31:06 PM
Uh, I think we’re missing each other - I was referring to the hard chromed inner tubes vice the aluminum “sliders”!

Although I really like to look of polished fork sliders, my next set will get painted black. 
I was referring to the tubes not sliders. I was seeking confirmation of my understanding of linnishing which is, that a minute amount of oil is retained on the tubes (above the seal) which has the effect of increasing the life and efficiency of the seals.