caliper & fork oil question

[mr blackstock]

I have a FJ1100 1984
I recently dismantled the front calipers and replaced the seals, there was a little scoring on the pistons, but I believed they might be alright as they were not deep.   The trouble is, I have reassembled the calipers, and there is leakage around where the calipers bolt together when I attempt to bleed the brakes.   Do other FJ riders use a sealing compound like silicon when bolting the two halves together?  And is it general opinion that the pistons need replacing even with small scores?

Also, concerning fork oil... My manual recommends 10w oil, this seems too light.  in my XJ650 I use 20w with great success, what weight fork oil do most use riding on poor surfaces?  I am thinking of putting in 20w and seeing how that goes.  (the anti-dive units are blanked off too.)

any thoughts would be appreciated,
cheers

[andyb]

For the calipers, if the pistons aren't deeply scored, usually you can take emery cloth or the like and buff out the scratches.  The seals will accommodate small dips in the metal if they're smooth, but sharp-edged scrapes and nicks will screw the seals in short order.

Don't know anything about what's between the halves, never took one of that type apart that far.

10W was the oem fork oil.  I'd suggest baby steps with it, up to either 12 or 15.  You can also adjust how it acts right at the end of the stroke by decreasing the air gap (more oil in it).  Different machines will use different grades in part because the orfice sizes will be different, so don't be deceived by another bike having good luck with vastly different oil in it.  Once you've gotten things buttoned up, it's not a big job at all to do the oil in them if you want to swap grades, it's the seals that are a bastard, so take baby steps and see how things feel under various conditions, experiment until you're happy.  If my memory isn't shot (questionable), I think I put the forks on my 90 back together with 1/2" less air in it and 10w30, which worked very well on super-rough pavement (midwest frost heaves in concrete are the devil!)--but that was coming from one fork being bone dry and the other having perhaps a cup of what appeared to be burned gear lube in it, so ymmv.

[mr blackstock]

Thanks for the tips, one final question... you mentioned using 10w 30, the manual suggests the same, 10w 30 motor oil.  I have never used motor oil in forks, just fork oil.  Although perhaps the difference is small enough not to worry about.
Is it common to use 10w 30 motor oil in forks, 'cause if it is it will save me around $60 compared to fork oil!

cheers

[andyb]

Some bikes specify motor oil of varying weights, some spec ATF, some spec straight weight oils.... it's just a question of if you're cheap enough to try it like me

[RichBaker]

I have a FJ1100 1984
I recently dismantled the front calipers and replaced the seals, there was a little scoring on the pistons, but I believed they might be alright as they were not deep.   The trouble is, I have reassembled the calipers, and there is leakage around where the calipers bolt together when I attempt to bleed the brakes.   Do other FJ riders use a sealing compound like silicon when bolting the two halves together?  And is it general opinion that the pistons need replacing even with small scores?

Also, concerning fork oil... My manual recommends 10w oil, this seems too light.  in my XJ650 I use 20w with great success, what weight fork oil do most use riding on poor surfaces?  I am thinking of putting in 20w and seeing how that goes.  (the anti-dive units are blanked off too.)

any thoughts would be appreciated,
cheers

O-rings only!!  I wouldn't use any silicone sealer ANY place on the bike..... factory seals, gaskets, etc. Silicone is a good way to ruin any thing mechanical.

For the forks, I'm running 15wt, Race Tech emulators and 1.0kg/mm springs.  Great combination....

[carsick]

will save me around $60 compared to fork oil!

cheers

Ummm, that's some spendy fork oil. A quart (or Liter depending on manufacturer) will do both forks. Even I caved and bought real fork oil instead of using my jug of recycled ATF and it was only $11! Am I missing a whole 'nother world of fork oil? It's not Harley oil is it??
Doug

[SlowOldGuy]

How did the small o-rings that seal the caliper halves look?  I recall having a little seepage when I split my '85 calipers, but it eventually stopped.  Just be sure it doesn't get on any paint!.

I might still have my stock calipers squirrelled away somewhere.  Where are you?

DavidR.

[Copterdriver]

Thanks for the tips, one final question... you mentioned using 10w 30, the manual suggests the same, 10w 30 motor oil.  I have never used motor oil in forks, just fork oil.  Although perhaps the difference is small enough not to worry about.
Is it common to use 10w 30 motor oil in forks, 'cause if it is it will save me around $60 compared to fork oil

Last weekend I changed my fork oil and used 10W30 on a '85 FJ1100 with no fork mods. By how much oil drained out I'd say the level was low and it had been a while since the oil was changed. I am really pleased with the ride, firm but not stiff.

Mike

[mr blackstock]

There are some good hints here! I might try the 10w 30, if people have not had too many issues with using it, then it cannot be that bad.

Concerning the calipers, I dismantled them, checked the "O" rings are o.k, then gently sanded the mating surfaces with wet n dry on some glass, they went back together o.k, solved the leak, but noe there is fluid coming from the piston area!

I am thinking of using some "protex" liquid metal to fill in the scores, just a little, as the pistons are very expensive, any suggestions???

cheers

[andyb]

Brakes get hot.  Like, really, really hot. 

If the scoring isn't terribly deep on the pistons, I'd suggest polishing them rather than anything else.  Do not go radially around the piston (which would of course be the easiest way), instead go up and down on them and think of what kind of surface the seals are going to see.  They can handle a bit of movement, but they can't handle hitting sharp corners (which is what you'd cause if you went around the piston instead of along it).

Depending on how bad they are, I'd start with 600 grit, then 1200, then probably scotchbrite, and then a fairly rough polish.  You're not looking for a chrome shining finish, you're just trying to make things reasonably smooth so the rubber has an easier time of it.  Same idea as polishing forks.  If the dings are too deep, the seal won't have enough travel to manage, and it'll leak no matter what you do, so there's really no harm in trying to save what you've got.

If they're really bunged up or whacked out of round or whatever, replacements are your only real options.  Because it's an 84, you're a little more limited on replacement options as compared to the newer models, but there's probably an entire set of calipers out there for a reasonable price from someone who upgraded their front end.  While you're looking though, don't discount the possibility of doing a full front swap from the sliders down from a later model FJ if you can find one at the right price.

[jack02]

Brake caliper O-rings....  when I had mine apart last year,the recesses in which they sat had some white,crystalline deposits (evaporated brake fluid residue?) which I figured would stop the O-rings from seating properly when I put them back in. I didn't procure new rings but left them to soak in brake fluid for a few days whilst I got to work with a box of toothpicks and the work's airline to remove every trace of said deposits. Whilst they were apart I noticed that the faces of the pistons which push against the brake pads were rusty and a little chewed up,so I restored those by removing just as much as I had to by pressing them against a belt sander whilst trying by eye to keep them 'square' for obvious reasons. The pistons themselves were cleaned up by using nothing more than Scotchbrite. Took a while but gave excellent results. Also used the toothpick to clean out the grooves where the piston seals reside,finishing off by using the works airline again. Being as tight as a gnat's chuff I didn't bother replacing the piston seals, (as far as I know they're original!) and to date I've got leak-free brakes which work exactly how they should. Can't say the same for my forks - when I fixed a leaky seal a few years back I somehow failed to tighten up properly the Allen bolt right at the bottom of the right fork leg,which loses one drop of oil every week or so! Doesn't sound much but over the years there'll be much less oil in the right leg than the left.... the detrimental effects of such a situation would advance at such a glacial rate that I can't tell there's something amiss by riding. Going to fix that when spring arrives in the UK.

[rktmanfj]

Brake caliper O-rings....  when I had mine apart last year,the recesses in which they sat had some white,crystalline deposits (evaporated brake fluid residue?) which I figured would stop the O-rings from seating properly when I put them back in. I didn't procure new rings but left them to soak in brake fluid for a few days whilst I got to work with a box of toothpicks and the work's airline to remove every trace of said deposits. Whilst they were apart I noticed that the faces of the pistons which push against the brake pads were rusty and a little chewed up,so I restored those by removing just as much as I had to by pressing them against a belt sander whilst trying by eye to keep them 'square' for obvious reasons. The pistons themselves were cleaned up by using nothing more than Scotchbrite. Took a while but gave excellent results. Also used the toothpick to clean out the grooves where the piston seals reside,finishing off by using the works airline again. Being as tight as a gnat's chuff I didn't bother replacing the piston seals, (as far as I know they're original!) and to date I've got leak-free brakes which work exactly how they should. Can't say the same for my forks - when I fixed a leaky seal a few years back I somehow failed to tighten up properly the Allen bolt right at the bottom of the right fork leg,which loses one drop of oil every week or so! Doesn't sound much but over the years there'll be much less oil in the right leg than the left.... the detrimental effects of such a situation would advance at such a glacial rate that I can't tell there's something amiss by riding. Going to fix that when spring arrives in the UK.

Dental picks work well for that kind of stuff... sometimes you can get an old one free for the asking.

Randy T
Indy

[rktmanfj]

Brake caliper O-rings....  when I had mine apart last year,the recesses in which they sat had some white,crystalline deposits (evaporated brake fluid residue?) which I figured would stop the O-rings from seating properly when I put them back in. I didn't procure new rings but left them to soak in brake fluid for a few days whilst I got to work with a box of toothpicks and the work's airline to remove every trace of said deposits. Whilst they were apart I noticed that the faces of the pistons which push against the brake pads were rusty and a little chewed up,so I restored those by removing just as much as I had to by pressing them against a belt sander whilst trying by eye to keep them 'square' for obvious reasons. The pistons themselves were cleaned up by using nothing more than Scotchbrite. Took a while but gave excellent results. Also used the toothpick to clean out the grooves where the piston seals reside,finishing off by using the works airline again. Being as tight as a gnat's chuff I didn't bother replacing the piston seals, (as far as I know they're original!) and to date I've got leak-free brakes which work exactly how they should. Can't say the same for my forks - when I fixed a leaky seal a few years back I somehow failed to tighten up properly the Allen bolt right at the bottom of the right fork leg,which loses one drop of oil every week or so! Doesn't sound much but over the years there'll be much less oil in the right leg than the left.... the detrimental effects of such a situation would advance at such a glacial rate that I can't tell there's something amiss by riding. Going to fix that when spring arrives in the UK.

Dental picks work well for that kind of stuff... sometimes you can get an old one free for the asking.

Randy T
Indy

What I meant to say was like the real steel ones that the dentist uses... mine gave me some he was just going to throw out.

Randy T
Indy

[jack02]

Randy you're right about the dental instruments - I've got loads because in a previous life I used to be a dental technician! I did use the steel dental picks to very gently probe the part of the seal recess where a wooden toothpick can't get,but was paranoid about scratching the alloy so used the wooden picks wherever they were sufficient for the job. But you dont need access to dental equipment - a bent pin would do the job so long as you're ultra careful .

[Mark Olson]

The pick and hook tool can be bought at any auto parts place. It is used for removing o-rings and seals.

no need to go all "Marathon Man"    "Is it Safe?"