Forks, Servicing, rebuilding, etc. Multiple Models

[Eric The Leg]

Personally, forks have always been a weakness for me. I feel like this is probably my biggest shortcoming as a motorcycle owner (other than not enough bikes)
My first rides had little-to-no suspension, and I learned at an early age how to pick the path for my front tire, and adjust for what I knew was coming, and then later with my 400, to just pick up the front end over the bumps in many cases.
Cornering is about the only place that I ever really rely on the front suspension, and once my fat rear end has the forks pushed down pretty well, the tire tends to track with the ground regardless of setup, maintenance, etc. (not saying I don't maintain, change oil, seals, etc, I do that, probably a little less frequently than I should, but it does get done).

I have an understanding of the basics:

• Springs should match the weight of the rider (and riding style). Several sites will suggest spring rates, so calculating my own spring rate is probably beyond the scope of my intent for this thread.
• Fixed rate springs that match the rider are ideal, progressive rings are more flexible, for multiple riders and/or styles, but will travel differently (feel more bumps, potentially less functional travel for some riders).
• Heavier oil increases dampening, thinner oil reduces it (and that dampening is, in brief, controlling how quickly the spring rebounds, which helps keep the wheel on the ground at the top of bumps, and helps prevent bottom-out).
• For forks that can be pressurized, that allows for added adjustment that's a little more limited, dynamic and fine-tuned compared to swapping springs.
• There are various sleeves/valves/etc that also impact dampening, admittedly those are 90% mystery to me though.

What's a good resource out there on forks?
Also, what 'tells' do you use to know when your forks are "on" or "off".

 

[ruwfo]

My first rides had little-to-no suspension... Fixed rate springs that match the rider are ideal, progressive rings are more flexible, for multiple riders and/or styles

Ah grass hopper then you have learned more then you think. Having the bike aka the suspension, set up for you is oh so important.
An example is; too much oil or too heavy of a spring , beats the crap out of you as you ride. Now you can learn to live with this,
(dumb) or you can set the bike up correctly.

The manufactures do a decent job of getting the setting close for a average rider, lets say a 180lbs rider, but what if your 220, then the
suspension going to feel on the soft side and bottom easier, maybe too much. The reverse if you weight 150.

You need to fine tune things, oil weight, spring height, spring dampening etc to suit you. This can be done, by having a starting point,
with good working parts, aka no blown fork seals, leaking shock etc. Ride the bike, were you normal ride & feel what it's doing, are
the forks always near bottoming? (put a zip tie on your fork leg & see how much travel you using), does the back end hop up when
hitting ruts. Spent an afternoon, adding a little fork oil if there bottoming, take some out if it's too harsh, etc.
But remember change one thing at a time so you can more easily feel the differences your changes are making and right down what
your doing.

Also read up on what things like: ride height, suspension sag , etc are, learn the terms, so when you get to a point you need more help, calling someone like Drew Smith , can guide you & him to get you bike perfect for you.

 

[Bigbill]

The compression of the suspension should be equal front to rear. I stand on a box and hold the bike vertical and push down on the left peg. Being even on compression means it won't ride like a hobby horse back and forth. I used the progressive rear shocks on a few of my mid to late 70's bikes. I used the stiffest springs they offered at the time when I was a 300lb rider. I changed the front oil till the suspension equaled out or as close as I could get it.(35mm fork)

When ordering shocks and springs make sure your getting the correct length of springs for the travel of the shock. I seen one PO use 17.5" springs on a 15.5" shock. The shocks never compressed. It was a Mack truck ride on a rocky road.

 

[justintendo]

setting sag and ride height is pretty key...as you mentioned, using the right springs and adjusting them correctly. after that comes anything to do with damping.
standing on a box and pushing down on the peg is not how ive ever seen setting sag described.

 

[jimspac]

There is the sag of the bike on it's wheels with no rider weight on it and secondary is the additional sag with the rider weight compressing the suspension further in stationary condition

 

[jo360]

Never rebuilt conventionals but start with correct rate spring for your weight ,new oil I Use atf front and rear, check/clean ever component the nuts that hold the valves in place will need the thread deburring before removal.you can source relevant information from the net but if your spring is correct and oil in good condition and you find the fork harsh then lighten the compression stack by changing the shims to allow the oil an easier pathway,you can modify float to give better high speed movement or modify the stack to allow more flex on the larger shims.all the motocross stuff needs more high speed and less overall compression usually remove a few of larger shims and place a smaller set under the large to allow the larger shims to flex.reduce oil height.I usually have to change things 3 or 4 times before getting things where iam happy.some valves are a bad design (45 shivers) and need larger ports.

 

[SteveJ]

A few years ago, I bought and downloaded Race Tech's Motorcycle Suspension Bible. Really helped my understanding of suspension systems, starting from basic concepts and progressing from there. Certainly helped me improve the handling/ setup of my 500. Discusses difference in the effects of spring rate vs. preload, damping, race sag, etc.
You might want to consider the book.

 

[suprize]

huskys like a heavy oil. I was a 7.5 user then 10 now im trying 15 having ridden a set up with 15 wt and was impressed. im only 85kgs

 

[Eric The Leg]

A few years ago, I bought and downloaded Race Tech's Motorcycle Suspension Bible. Really helped my understanding of suspension systems, starting from basic concepts and progressing from there. Certainly helped me improve the handling/ setup of my 500. Discusses difference in the effects of spring rate vs. preload, damping, race sag, etc.
You might want to consider the book.

Just ordered a used copy off of Amazon!

 

[Bigbill]

With the new bikes with 12" of suspension travel they set the rider in full gear at 4" of sag? That's 1/3 of the suspension travel. Do we do the same on the evolution bikes or adjust the spring weight to the riders weight and live with it?

I just ordered the race tech suspension book too. I wish there was a book for older suspension setting. I can't adjust every bike for my weight. I want to let others experience the Husqvarna ride too. Maybe I can hit a happy medium between a 180lb rider and a 250lb rider setting.

If you look at the US ARMY 155mm Howitzers I built many parts units for them one is the twin nitrogen filled shocks to absorb the recoil when she fires. I also worked on elevator buffers there a big shock that a piston goes down a tube with less and less holes for the oil to escape. Incase of an elevator runs away into the pit.
I'm sure with all my machine building experience I can rebuild a dirtbikes rear shock.

I have a little experience with front forks. The Japanese really took front forks to a new level with replacement wear sleeves. It's all rebuildable.

With everything said here I wonder how many riders really tune there suspension when they purchase a new bike. I'm sure the play riders don't even set the sag.

 

[jo360]

Makes a huge difference, we ride on fast 4wd tracks rock and hard pack clay covered in pea gravel lots of wash outs, boulders, rutts and woops, two motocross guys pulled up beside me as i was unloading the husky.
They had brand new crf450s they proceeded to do some stretches and then unload their bikes,they eventually set off after warming up the bikes, so i followed behind watching them bounce around on ultra stiff suspension slamming into the washouts back end tossing them sideways the only way they could keep it together was by slowing down, i got bored so passed them and carried on got over two more hills and then doubled back they were still coming down the second one, these guys could obviously ride but their set up was for a groomed motocross track, i have two crf450s both set up for off road both as fast as the husky kyb and showa took 2 rebuilds on the showas and 4 rebuilds on the kybs but worth the effort.

 

[justintendo]

Makes a huge difference, we ride on fast 4wd tracks rock and hard pack clay covered in pea gravel lots of wash outs, boulders, rutts and woops, two motocross guys pulled up beside me as i was unloading the husky.
They had brand new crf450s they proceeded to do some stretches and then unload their bikes,they eventually set off after warming up the bikes, so i followed behind watching them bounce around on ultra stiff suspension slamming into the washouts back end tossing them sideways the only way they could keep it together was by slowing down, i got bored so passed them and carried on got over two more hills and then doubled back they were still coming down the second one, these guys could obviously ride but their set up was for a groomed motocross track, i have two crf450s both set up for off road both as fast as the husky kyb and showa took 2 rebuilds on the showas and 4 rebuilds on the kybs but worth the effort.

classic!
im sure they were surprised the ol girl soaked up the terrain!

 

[Bigbill]

If I purchased a newer bike I would send out the suspension to be setup for my weight. My new 98 Husqvarna 250wr was impossible to ride in any kind of trails. The '99 TE610e Husqvarna dual sport was good on the street. Off road the shifter locked up in the tranny on the very first ride. After that was fixed by the dealer the outer oil pump housing turned and blocked off the oil pressure this killed the cam and rockers. I was so upset the dealer bought the bike back. Thank god I still had the old reliable left kickers.

Don't ya think the newer suspension is wa over built for a play rider? They will never set it up to its full function.

 

[jo360]

If I purchased a newer bike I would send out the suspension to be setup for my weight. My new 98 Husqvarna 250wr was impossible to ride in any kind of trails. The '99 TE610e Husqvarna dual sport was good on the street. Off road the shifter locked up in the tranny on the very first ride. After that was fixed by the dealer the outer oil pump housing turned and blocked off the oil pressure this killed the cam and rockers. I was so upset the dealer bought the bike back. Thank god I still had the old reliable left kickers.

Don't ya think the newer suspension is wa over built for a play rider? They will never set it up to its full function.

Probably 80% of the mx bikes will never see a mx track plushing up the suspension on these play ride bikes is big business the new air forks seem to be getting bad reviews and on long rides will loose pressure cc and oc forks are easy enough to work on messy jobs but worth it day and night difference when you get the right combination.
Play riders need good suspension just to keep them from killing themselves smashing into a tree or similar its complicated because its that important having said that some of the conventional forks are highly regarded and sort after because they work so well.going to rebuild my original husky 40mm forks and front end ready for vinduro season will do a comparison my only concern is the drum brake.

 

[jo360]

classic!
im sure they were surprised the ol girl soaked up the terrain!

They had all new gear on including colored reflective goggles but i can imagine the bewildered look on their faces.the more i push the husky the better it feels but riding to my limit gives me about 10 minutes riding before i have to back off, or i get tired and bike slaps me in the arse, last time was gravel rash through to the bone of my elbow.
I rebuilt the rear itc twice lightening the compression stack and increasing rebound dampening used a orbital sander to help get air out of the oil.

 

[Eric The Leg]

I'll openly admit to being a bit of a "play rider" Doesn't mean I don't like the ride to be smooth (or take a brief vacation from ground contact every once in a while). I was a decent size match for the guy I bought my '86 from back in the day, so it did ride nicely for me out of the gate. As I've gotten a bit heavier, too stiff isn't the problem, more the other direction.
I know my bikes and have confidence in my riding skill (I better after 20+ years with my '86) It wouldn't take too much to convince me to try out a Vinduro type event sometime. The proximity to other riders in an all-out race setting unnerves me though. You won't see me on an MX track (at-least during an event) any time soon.

The book is on the way, and I do have a spare fork set in the garage to practice on once I get a little time. If I'm not comfortable riding the shocks after reading the book and working on them, I could just cut to the chase and take my forks to the same shop that rebuilt my Ohlins. Won't be cheap, but there's a something to be said for the confidence that comes from getting the work done by someone who won't make the amateur mistakes that I might.

 

[Eric The Leg]

Quick question. Race Tech Gold valve, do or don't?
It's an added cost, but the nice thing is they then provide some stack calculations, which should lead to a nice starting point. While I'm sure that it would be an upgrade to the existing piston, I'm just wondering between my [low] skill level and background if I'd ever notice the difference.

 

[jo360]

What areas are your main gripe with the curent set up?, would play with what you have rather than spend money,at the moment suprize believes thicker oil can improve the fork this suggests that the valves/shim stack may be too free flowing diving and bottoming out or its possible the stacks have been changed by a po and or incorrect springs for your weight.better off with a heavier spring and less pre load.
Get all the info you can main issues, spring weight, pre load, shim stack oillevel, clickers. if you have a bike you think has better set up compare the two side by side with a helper have the helper bounce on the pegs of each bike and copare how the two differ in action.

 

[jo360]

Just had a look at my 40mm husky forks and not alot to work with single valve no shims and damping rod with different holes would have to agree with suprize and change oil viscosity and maybe a small spacer to compress spring or cut back spring and replace with spacer to make them stiffer, might be able to get more damping by restricting valve flow wih a backing washer and restricting the flow through the rod.mine felt like a pogo stick when pushing up and down on them so if yours are the same try 15 or 20 wt oil and fill 10% more than normal, plus side is these things are so easy to work on changing things should be a doddle.

 

[justintendo]

I'll openly admit to being a bit of a "play rider" Doesn't mean I don't like the ride to be smooth (or take a brief vacation from ground contact every once in a while). I was a decent size match for the guy I bought my '86 from back in the day, so it did ride nicely for me out of the gate. As I've gotten a bit heavier, too stiff isn't the problem, more the other direction.
I know my bikes and have confidence in my riding skill (I better after 20+ years with my '86) It wouldn't take too much to convince me to try out a Vinduro type event sometime. The proximity to other riders in an all-out race setting unnerves me though. You won't see me on an MX track (at-least during an event) any time soon.

The book is on the way, and I do have a spare fork set in the garage to practice on once I get a little time. If I'm not comfortable riding the shocks after reading the book and working on them, I could just cut to the chase and take my forks to the same shop that rebuilt my Ohlins. Won't be cheap, but there's a something to be said for the confidence that comes from getting the work done by someone who won't make the amateur mistakes that I might.

the front swede forks are super simple. much different than rear shocks or newer forks. if you can work on your bike you can work on the forks.