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Fork Spring Service

50K views 114 replies 31 participants last post by  Austellfz09guy 
#1 · (Edited)
DYI I found on how to make a fork spring compression tool.

If you plan on working on your forks then a fork spring compressor makes the job a little easier. Instead on paying nearly $50 its quick and easy to make your own compressor. With stock springs I could compress my forks by hand but after upgrading to stiffer springs it was not possible.

Supplies needed (less than $5 at Lowe's)

1. 2 1/2" or 3" PVC coupler
2. 3/8" threaded rod 12" long
3. 4 nuts to fit 3/8" rod
4. Motorcycle tie down

Next cut the threaded rod in half to make 2 6" rods. You need to form a point on one end of each of the rods. Use a grinder for this. Now using a 3/8" drill bit drill a hole through both sides of the PVC coupler. Place a rod through each hole with nuts on both sides to keep the rod from moving. On most forks there is a plastic spacer above the spring with 2 holes in it. This is where the pointed ends of the compressor fit. Make sure the rods are tight against the holes. Now you can press down (wear gloves) on the outer rods to compress the spring while another person places a wrench on the damper to help remove the fork cap.

Removing or installing the cap can be a one person job if you have a vise mounted to a bench. Place the fork in the vise. Place the spring compressor on the fork. You will need a tie-down looped under the vise with each end hooked over the PVC coupler and the threaded rod. Make sure the ends of the tie-down are over the threaded rod from opposite sides. Now start pulling on the tie-down strap and it will begin to compress the fork. I used one hand to pull the strap and the other to pull down on the spring compressor. It took a little time to get it right on the first fork but the second one was easy.

************

I plan making one on Sunday and will have pictures as soon as I finish.
 
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#7 ·
In the link they show the fork tube going into a vice to hold it... NO NO NO!!!
It's OK to put the axle block into a vice (and tighten lightly) but never the tube itself - they are so thin any amount of clamping will distort the tube.
The axle block is the part the axle goes thru - don't put any other section into a vice.

If you have to hold the tube, put it back into the triple clamp and tighten only to the torque specified - or put the top nut back into the tube and hold the nut.
 
#5 ·
I've been waiting for a fork thread! Question: How do you tell if your forks or steering is messed up and not just your handlebars?
 
#6 · (Edited)
In the old days we used a micrometer and a lathe to determine if a fork tube was bent. That method required a complete disassembly of the fork tubes. It is the only sure way to know. We used a drill press with a special collar to bend the tubes. Now tubes are much cheaper to come by, which would negate the press because it is labor intensive. Sometimes forks are just bound up in the triple clamps and can be loosened and twisted back inline.

Disclaimer: When I was a youth, I worked part time in the service department of the shop that I raced motocross for to offset the sponsorship arrangement they had with me.
 
#9 ·
Hey Mate,

I try to swap my springs last nigth and figure out pretty quick it wasn't going to be as easy as my FZ6R. Now I get why you need a compression tool! LOL I contact the bike shop here but they don't have time to do it before the holidays so that leave me one option...

I guess I'll make one too. Thanks...
 
#21 ·
I had to buy the big boy Sears allen socket set. $25 later and my disassembly is complete. I was lucky to have a 23mm wrench for the fork caps. I had a special wrench made for my dual chamber motocross forks but too big. Fork springs, 10W Maxima racing fork fluid, EBC HH pads, and Spiegler SS lines on deck.

Check out the reflective Red Yamaha stickers to replace to bicycle reflectors. They match the red and shine when light hits them.

 
#25 · (Edited)
Just changed the fork oil over, and having never done this with upside down cartridge forks before... can I just say what a pain in the @#$% it was. Took 5 hours total, but that included the time it took to come up with a spring compressor adapter - very similar to the ones shown here.
So just to recap:
1. To change the oil, you need a fork spring compressor - plan on that, or take it to a shop
2. There is no damping in the left fork leg except for the tiniest bit of compression damping at the bottom of the stroke, so only do the right one.
3. 10W oil seems to do the trick of preventing too much post bump rebound - as tested by plunging the forks on the front brake in the garage. But it is cold today (50'sF) so that might be different in summer.
4. Setting the damping screw so you get 3 turns is a little tricky, but do-able.

I don't want to have to do that again - hope it all works nicely

Edit to add pictures
...and I also highly recommend adding chain spray or your fave anti-sieze to all the bolts you remove. This will prevent the threads from stripping in the future.

















 
#26 · (Edited)
Hell yeah, thank you. It was a complete pain in the ass, nothing like the dual chamber motocross forks of my past.

My homemade tools, and I had to use crank type tie downs, I believe the wood method is more stable:



Be sure that it is level both ways before you suck out the fork oil.



My retractable magnet worked like a champ on the damper rod to get it back up through the spring; I did not have to screw it around the spring with a small wrench like the good old days, or use safety wire wrapped around the nut.

And, No, it is not tight in the vise, zipties to hold it while I get it level.
 
#28 ·
I like the screw and nut spring compressor Doug, better than the wood one I made - would have gone to the depot to get the parts but the bike was in pieces, it was actually raining here (very odd) and the wife had the car.
If I had a lathe, a welder etc etc etc...
It's a conspiracy I tells ya.

The workmate I was using is a very handy tool, bought it back in 1981. It adjusts to various heights, holds all kinds of odd things, is portable and folds away flat for storage. The wooden jaws got a bit messed up with various projects and this last one kind of ripped them out a bit more. Went to B&D's site to see if they had spares, but discontinued ages ago. Ordered a pair of their latest jaws and will cobble to fit.

While on their site, I was reading some reviews of their latest workmates from some lifelong users who had to buy the new version. Boy were they slamming the new made in China plastic versions, with missing welds and bits that break off. Sometimes new is not better.

and many thanks for your "help" with the other unmentionable thingy.
 
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#30 ·
The workmate I was using is a very handy tool, bought it back in 1981. It adjusts to various heights, holds all kinds of odd things, is portable and folds away flat for storage. The wooden jaws got a bit messed up with various projects and this last one kind of ripped them out a bit more. Went to B&D's site to see if they had spares, but discontinued ages ago. Ordered a pair of their latest jaws and will cobble to fit.
I use an old Workmate here on a daily basis. It's actually ideal for holding forks while they get bled, and it's multi-purpose. I will never be without it!

RichBinAZ wrote:



You are serious? I've never heard of that before.....using motor oil in the forks! What's the chance of it working properly.....I honestly don't have a clue?
ATF is another oddball that works well.
 
#40 ·
RichBinAZ wrote:

You are serious? I've never heard of that before.....using motor oil in the forks! What's the chance of it working properly.....I honestly don't have a clue?
Yea, sorry, I'm a bit rebellious like that. The only thing you have to watch for really are the seal and piston ring materials. I hope they are using Nylon 12 for the piston rings or better (low swell when submerged in oil) and NOT buna N for any O-rings or seals.

All the bikes in my sig and the ones before all the way back to the BSA A10 I had in the 70's ran with engine oil in the forks. In fact for the A10, it was the recommended fluid.
When I got my first Hondas, they ran with ATF - but what viscosity is that? Then came fork oil - didn't like that as the smell reminded me of cutting fluid used in lathes.

The Yamaha oil that came out of the forks looks really nice, felt smooth between the fingers but was really watery. I would not object to putting 10W Yamaha fluid in
Running the 10W today around the hood was a treat, no excessive rebound and that was with the screw 3/4 of a turn out from closed. It's nice to have extra damping capacity for when the temp goes from 60F today to 115F in 6 months from now.
 
#31 ·
Beautiful How-To Doug, i will print this out and use it as my guide when i change out my springs.
 
#32 ·
I can't take credit for that. It took me forever to get around to doing the service. Thank RichBinAz for the detailed instructions, as he saved me a bunch of time explaining.

Note: I would not lubricate the o-ring with WD-40, use fork oil on it.
 
#33 ·
On a side note. I put the 10w Maxima Fork fluid in both legs. The Maxima is a low stickion fluid, and I wanted both legs to benefit from the reduced stiction agents. I know that the factories haven't used fish oil in thirty years, but I still don't trust them to use high quality racing fluid.
 
#34 ·
Thanks Rich!
 
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