fork seal question

[5speed]

I'm baaaaack. lol
Took the fj for an mvi and one of the fork seals is leaking. I read thru the service manual I have and the section in the file forum and it seems pretty straight forward.
My one question I can't find an answer for is...is there anything that needs to be done with the anti-dive valve before or during the tear down?
Only 1 seal is leaking but I'm going to do both.

[red]

I'm baaaaack. lol
Took the fj for an mvi and one of the fork seals is leaking. I read thru the service manual I have and the section in the file forum and it seems pretty straight forward.
My one question I can't find an answer for is...is there anything that needs to be done with the anti-dive valve before or during the tear down?
Only 1 seal is leaking but I'm going to do both.

5speed,

Many a good seal has been saved by the Sealmate tool, or a homemade copy.  Dirt gets into the seal, then it leaks.  Remove the dirt, remove the leak.

The Anti-Dive unit just bolts on, with nothing going into the forks.  It only controls fork oil flow, if even that.  Lots of riders just replace them with cover plates, since the AD unit does almost nothing.  The hydraulic hose just goes straight to the caliper, then.  The cover plate will have to have an oil passage, which is usually just a slot on the inside surface of the plate.  A flat cover plate (without an oil passageway) would stop all fork oil flow, and "lock" the fork with no suspension action.  There are several sources for FJ Anti-Dive cover plates.

[FJmonkey]

The AD unit does not require service. Some have simply removed it to save un-sprung weight. But the front wheel is the heavy pig on the 84/87 years. How many miles on the clock? Might be time to change the bushings/bearings.  

[5speed]

Many a good seal has been saved by the Sealmate tool, or a homemade copy.  Dirt gets into the seal, then it leaks.  Remove the dirt, remove the leak.

The Anti-Dive unit just bolts on, with nothing going into the forks.  It only controls fork oil flow, if even that.  Lots of riders just replace them with cover plates, since the AD unit does almost nothing.  The hydraulic hose just goes straight to the caliper, then.  The cover plate will have to have an oil passage, which is usually just a slot on the inside surface of the plate.  A flat cover plate (without an oil passageway) would stop all fork oil flow, and "lock" the fork with no suspension action.  There are several sources for FJ Anti-Dive cover plates.

Tks for the info. I want to keep the bike stock so I'll just leave the anti dive valve alone.
I saw the seal cleaner on the RPM site. Might be worth a shot.
FJMonkey, she is showing 55000 miles.

[FJmonkey]

FJMonkey, she is showing 55000 miles.

You might consider the bushing/bearings as well. If not, the worst thing will be weeping past the seals. So keep an eye out for it. 

[Motofun]

With 55,000 miles on the clock and an unknown history I'd redo the whole shooting match.  The anti dive units were always junk.  All the extra hoses, fittings etc made the early models just that much harder to bleed and did little to nothing for handling.  To each his own, I guess.

[5speed]

With 55,000 miles on the clock and an unknown history I'd redo the whole shooting match.  The anti dive units were always junk.  All the extra hoses, fittings etc made the early models just that much harder to bleed and did little to nothing for handling.  To each his own, I guess.

I'm one of those "like to keep it factory" unless it involves improving the safety or performance of a vehicle.
I could never cut up a classic car unless it was a "mass produced, everyone's grandfather owned one" vehicle.
My 86 IROC is stock except for sub frame connectors and the engine.
ETA..I will do seals and bushings. tks for the suggestion folks.

[fj1289]

I would also very seriously consider the fork valves and springs while you are in there.  The FJ fork springs are very weak - and contribute to the throttle control challenges with the FJ.  Simply rolling on or off the throttle with the stock setup will cause the front end to rise and fall 3+ inches  -  definitely not the chassis behavior you are look for!

If the valves are out of the budget then definitely do the fork springs.  If you later add the valves just know you will need new springs again - springs that work with the valves won't play well with the stock damping and vice versa. 

Fork valves and springs are right up your alley - stock looks, modern bike performance!

[Flynt]

With 55,000 miles on the clock and an unknown history I'd redo the whole shooting match.  The anti dive units were always junk.  All the extra hoses, fittings etc made the early models just that much harder to bleed and did little to nothing for handling.  To each his own, I guess.

I'm one of those "like to keep it factory" unless it involves improving the safety or performance of a vehicle.

I had the same intent with my '84 and worked at getting the AD valves working as they should...  most don't, so you want to go through them fully.  After I had them working, they did provide the advertised AD function, at least enough to notice adjustments to the dials.  However it came with a significant delay and decrease in effectiveness of the front brakes (compared to my '92 anyway).  I swear I could feel the little AD piston moving through the lever as I was waiting for the brakes to engage...!  Once I tried the AD setup with some actual pace, I ran the brake lines right to the calipers and flipped the AD units over in place (gives you the hydraulic bypass through the valve without the "open" looking part on the top) and I had brakes!  Getting those things out of the front braking system reduces the potential failure points and increases the performance of your most critical safety system...  I think it qualifies.

While I admire you intent, you're not going to get real AD functionality AND the best front brake performance out of those things.  I spent months proving this to myself FWIW.  I got block off plates and stored the AD units in case the next owner would like to have them.  Then I went with the RPM valves and springs.  The setup gives modern suspension performance including dive resistance, while dramatically increasing control of the front wheel through all manner of conditions...  another safety and performance upgrade.

I'd recommend giving up on the AD units at least...  time better spent riding.

Frank

PS - I still have stock master and calipers, but went to better rotors and pads (also from RPM).  It brakes hard with one finger now.

[5speed]

I had the same intent with my '84 and worked at getting the AD valves working as they should...  most don't, so you want to go through them fully.  After I had them working, they did provide the advertised AD function, at least enough to notice adjustments to the dials.  However it came with a significant delay and decrease in effectiveness of the front brakes (compared to my '92 anyway).  I swear I could feel the little AD piston moving through the lever as I was waiting for the brakes to engage...!  Once I tried the AD setup with some actual pace, I ran the brake lines right to the calipers and flipped the AD units over in place (gives you the hydraulic bypass through the valve without the "open" looking part on the top) and I had brakes!  Getting those things out of the front braking system reduces the potential failure points and increases the performance of your most critical safety system...  I think it qualifies.

While I admire you intent, you're not going to get real AD functionality AND the best front brake performance out of those things.  I spent months proving this to myself FWIW.  I got block off plates and stored the AD units in case the next owner would like to have them.  Then I went with the RPM valves and springs.  The setup gives modern suspension performance including dive resistance, while dramatically increasing control of the front wheel through all manner of conditions...  another safety and performance upgrade.

I'd recommend giving up on the AD units at least...  time better spent riding.

Frank

PS - I still have stock master and calipers, but went to better rotors and pads (also from RPM).  It brakes hard with one finger now.

Tks for the advice..I won't be doing that this year but will collect up the necessary parts over the winter.
I don't have anything to compare the steering and handling of it as I've never owned a sport bike or one with AD options and I've only had the fj out 3 times so far.
Is there a source for the block off plate or is it a DIY thing?
fj1289..thanks for the tip..

[Flynt]

I had the same intent with my '84 and worked at getting the AD valves working as they should...  most don't, so you want to go through them fully.  After I had them working, they did provide the advertised AD function, at least enough to notice adjustments to the dials.  However it came with a significant delay and decrease in effectiveness of the front brakes (compared to my '92 anyway).  I swear I could feel the little AD piston moving through the lever as I was waiting for the brakes to engage...!  Once I tried the AD setup with some actual pace, I ran the brake lines right to the calipers and flipped the AD units over in place (gives you the hydraulic bypass through the valve without the "open" looking part on the top) and I had brakes!  Getting those things out of the front braking system reduces the potential failure points and increases the performance of your most critical safety system...  I think it qualifies.

While I admire you intent, you're not going to get real AD functionality AND the best front brake performance out of those things.  I spent months proving this to myself FWIW.  I got block off plates and stored the AD units in case the next owner would like to have them.  Then I went with the RPM valves and springs.  The setup gives modern suspension performance including dive resistance, while dramatically increasing control of the front wheel through all manner of conditions...  another safety and performance upgrade.

I'd recommend giving up on the AD units at least...  time better spent riding.

Frank

PS - I still have stock master and calipers, but went to better rotors and pads (also from RPM).  It brakes hard with one finger now.

Tks for the advice..I won't be doing that this year but will collect up the necessary parts over the winter.
I don't have anything to compare the steering and handling of it as I've never owned a sport bike or one with AD options and I've only had the fj out 3 times so far.
Is there a source for the block off plate or is it a DIY thing?
fj1289..thanks for the tip..

I used some that look like these...  but I don't recall where I got them.

https://tractechmfg.com/product/fj1100-anti-dive-by-pass-plates/

You can disable the AD unit by taking the part with the brake lines off, route the lines from master to caliper directly, and the AD body itself allows the fluid to bypass.  Flipping them vertically puts the knob on top and makes it look "finished".

Frank

[5speed]

I used some that look like these...  but I don't recall where I got them.

https://tractechmfg.com/product/fj1100-anti-dive-by-pass-plates/

You can disable the AD unit by taking the part with the brake lines off, route the lines from master to caliper directly, and the AD body itself allows the fluid to bypass.  Flipping them vertically puts the knob on top and makes it look "finished".

Frank

Tks.
Are the 1100 block off plates similar to the 1200? From the look of that design a flat block off plate won't work.

[red]

I've never owned a sport bike or one with AD options and I've only had the fj out 3 times so far.  
Is there a source for the block off plate or is it a DIY thing?  fj1289..thanks for the tip..

5speed,

This design for the AD block-off plates should do the job as well:

 

Contact FJ1200W here (maybe by PM?) and see if he has seen enough interest in AD plates to make some sets.  The "cooling fins" on the front side is purely decorative.
The slot on the back is a fork oil passage, gotta have that.  If the sealing gasket does not run all the way around the edge of the AD plate position, you may need a DIY gasket cut to fit the back of the AD plate, and open at the fork oil passage.
.

[5speed]

I've never owned a sport bike or one with AD options and I've only had the fj out 3 times so far. 
Is there a source for the block off plate or is it a DIY thing?  fj1289..thanks for the tip..

5speed,

This design for the AD block-off plates would do the job as well:

   

Contact FJ1200W here (maybe by PM?) and see if he has seen enough interest in AD plates to make some sets.  The "cooling fins" on the front side is purely decorative.
.

Are those 3D printed or is that a file for cnc?

[Pat Conlon]

I used some that look like these...  but I don't recall where I got them.

https://tractechmfg.com/product/fj1100-anti-dive-by-pass-plates/

You can disable the AD unit by taking the part with the brake lines off, route the lines from master to caliper directly, and the AD body itself allows the fluid to bypass.  Flipping them vertically puts the knob on top and makes it look "finished".

Frank

Tks.
Are the 1100 block off plates similar to the 1200? From the look of that design a flat block off plate won't work.

Same AD valve used on the '84 thru 87 FJ's.
https://www.partzilla.com/product/yamaha/36Y-2319E-00-00

Related Fitment

This Yamaha 36Y-2319E-00-00 DAMPER PISTON ASSEMBLYASSY fits the following models and components:

Yamaha Motorcycle 1986 FJ1200S FRONT FORK

Yamaha Motorcycle 1984 FJ1100LC FRONT FORK

Yamaha Motorcycle 1985 FJ1100NC FRONT FORK

Yamaha Motorcycle 1987 FJ1200TC FRONT FORK

Yamaha Motorcycle 1987 FJ1200T FRONT FORK

Yamaha Motorcycle 1985 FJ1100N FRONT FORK

Yamaha Motorcycle 1984 FJ1100L FRONT FORK

Yamaha Motorcycle 1986 FJ1200SC FRONT FORK