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 Fork tuning and set up 
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Joined: 12 Sep 2008, 14:04
Posts: 326
Post Fork tuning and set up
Some helpful tips we have found on the web...


The first thing to do when setting up your dirt bike suspension is to put the rebound and compression clickers for both the forks and rear shock in their standard position (your owners manual should tell you how many clicks out is standard), if you don't have the manual just set them halfway between hard and soft.

If possible find out what the standard rear spring was for your bike and make sure that's what is in it now. If you've bought your bike secondhand and the rider who owned it before you was heavier or lighter than you or was particularly fast then they may have put a different spring in it which can make dirt bike suspension tuning difficult, this can be the case for the forks as well.

To set the static sag on the rear shock you first need to set the preload.
Back off the locking ring and then you either tighten or loosen the main ring to increase or decrease the preload on the shock.
Put the bike on a stand with the rear wheel off the ground and measure from the axle nut to a point roughly above it on the bike (say, a mounting bolt for the muffler or a part on the rear subframe), now take the bike off the stand and let it stand upright.


With the bike off the stand now measure the distance between the axle bolt and the point on the bike itself.
Subtract that measurement from the distance measured when the bike was on the stand, there should be about 25mm of sag, if there's more than that wind up the preload or if there's less then back it off. This measurement is called static sag.

Now to set the laden sag (race sag). Take note of the measurement with the bike standing upright. Now with all your riding gear on sit on the bike in the attack position (head roughly over the crossbrace, elbows up and out and feet up on the pegs), have someone hang onto the bike for you and take a measurement again. The amount of sag should be between 90mm and 110mm, again if it's more or less then adjust the preload etc.

You should be able to get it set up approximately to those figures, if it's way out on either then that can indicate that it either has different springs than standard (if you bought the bike secondhand) or that you're heavier or lighter than the model used by the bike manufacturers. They base their settings on a theoretical rider who is about 5'10" tall and about 85kg.

These are just rough figures, read your owners manual for the bike, the japanese manufacturers have a decent section in their manuals on dirt bike suspension.

Taking some time to learn about and set up your dirt bike suspension costs nothing and can really improve your lap times.

****Here is a helpful step by step way to service your PITSTER PRO GPX FORKS.


The following oil weights and volume are general suggestions only. You may need to tweak your own combination to
achieve the best results for you style riding and weight.
Rider Weight Oil Weight Oil Volume per Leg
<100# 5wt 80cc
100-130 10wt 100cc
130-180 20wt 120cc

Tools Needed:
6mm Allen wrench
5mm Allen wrench
(2) 17mm open end wrenches
15/16 low socket
Plastic bucket
Ratio Rite cup that has ml and cc's
Fork siphon or syringe
20wt synthetic fork oil I use Torco products
"Jeremiah Staggs" uses 80wt BelRay Gear Oil with anti shear additive this has the same consistency as
20wt fork oil and has anti-shear added.

Here we Go:
(1) Start off by removing only one of your fork legs at a time. This is because some may get confused and
I like to allow for proper Fork height alignment when reinstalling.
(2) With Fork Leg Removed and in a Vertical position:
(3) Remove the top cap with a 15/16 standard short socket carefully "while it’s still vertical. with this done
and the top cap off slowly pull the cap up till about 6 inches of the spring is visible and let gravity drain
into a plastic bucket:
(4) after a few minutes take a clean rag and wipe the (2) Nuts off below the cap and draw a mark on both
nuts across from each other. This is to ensure that you get the correct height adjustment back to the
Metering Rod (Dampening Rod) back to the correct position to where you started with.

(5) Now take the (2) 17mm wrenches and unscrew the top cap from the spring assembly (counting the
number of turns you made past the marks on the nuts) and slowly separate the assembly (making sure
not to bend or damage the Dampening rod):
(6) Completely remove the rod and set it aside and (again do not drop or bend the rod) and let the rest of
the Fork assembly gravity drain into the plastic bucket for 5 min or so. Now take the fork leg while over
the Bucket and slowly pump the fork tube in and out and you will notice (where the dampening rod goes
in) the oil will drain out of it....and also the lower fork tube Do this many many time till no more oil comes
out. (don’t worry about the spring assembly falling out as its attached to the lower leg with a Allen bolt):

Next step is get the Fork oil and Ratio Rite cup and Syringe and pour (no more than between 75cc and
100cc of 20wt fork oil (150lb---200lb) riders also 15wt oil can be used also for less (120lb---150lb) riders
and play with the oil levels as needed add or subtract between 75cc and 100cc:
(7) Now with 99.9% of the used fork oil drained and the fork tube in the collapsed position and standing
vertical. Fill the Fork (siphon/syringe) and start adding fork oil to dampening rod tube:
Courtesy of Outlaw Powersports
And continue this till all (between 75cc----100cc) (150lb---200lb) of fork oil is used. this might take 3 or 4
times with the Syringe (DO THIS VERY SLOWLY AS NOT TO GET IT ALL OVER THE PLACE OR IN YOUR
EYES):
Now with the Fork tube assembly still Vertical give it a few minutes it will partially bleed itself of air
bubbles (not completely). Now carefully wipe down the Dampening rod and cap assembly and insert it
slowly down the Dampening tube. Now thread it back together counting the number of turns from
disassembly and tighten it back to the marks you made on the 2 nuts till they are opposite from each
other. And carefully use the 15/16 shallow socket to thread the top cap back to the fork tube so it looks
like this again:

(8) Now with the fork leg assembled I pumped it continuously in several different "Click" settings to help
Bleed the air from the forks (they will continue to bleed themselves) on your bike also
(9) Replace the fork tube back into your triple clamps and remember to Torque the bolts to proper specs.
And move on to the other fork Tube assembly.
*Note: while the Forks are apart you can continue to disassemble the spring and dampening tube
assembly and clean all the part and get ride of any excess oil. And upon reassembly of these parts
Remember to get the correct Height adj of the Dampening Rod, spring, Dampening Rod shaft and top cap
back to the correct Adj length.

_________________
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http://www.pitsterpro.com


29 Sep 2008, 16:03
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Joined: 29 Sep 2008, 16:50
Posts: 9
Post Re: Fork tuning and set up
I'm putting 10wt fork oil in my motard forks and I'll post up how they are.


29 Sep 2008, 16:54
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Joined: 29 Sep 2008, 16:50
Posts: 9
Post Re: Fork tuning and set up
New oil really improves these forks alot. the main thing I noticed was they seemed to be a bit smoother.


21 Nov 2008, 17:02
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Site Admin

Joined: 12 Sep 2008, 14:04
Posts: 326
Post Re: Fork tuning and set up
How to service your Conventional forks (CRf 70) style

Step 1: Put your bike up on a stand to where the front end will hang off the floor. Then if you have a front drum brake remove the brake cable from the front brake lever. If you have a front disc brake remove the caliper from the caliper bracket and place a small wedge or piece of thick cardboard between the brake pads (this is so the caliper can not be mistakenly applied.

Step 2: Remove the front wheel loosen the axle remove it (pay attension to which side the wheel spacers go on) if the axle will not slide out easly then tap it out with a rubber mallet and and drift and set the wheel aside along with the brake drum and brake cable or the front brake disc

Step 3: now if you have disc brakes remove the caliper and let it just hang out of the way. also its good to remove the front number plate just so you have clear access to the all the bolts.

Step 4: now it a real good time to loosen the nut on top of the fork tubes on each fork as its a lot easier to loosen while they are held by the tripple clamps.

Step 5: use the correct size socket or wrench to loosen the left side of the upper top clamps (pinch bolts) and the lower bolt on the lower left side clamp (do one side at a time). now slide the fork tube out of the clamp and over to your work area.

Step 6: Now with one side off its time to take it apart , nows agood time to have someone else around to be able to hold the forks upright. but not nessesary. with the fork in the upright position on on the floor of your work area. remove the top nut off the top of the fork tube. remember the fork is spring loaded and has fluid inside.

Step 7: now with the Cap off the fork, place the complete fork assembly over a large bucket or Pan and pull the fork spring out of the fork tube... the bucket is there so you do not make a mess. Now set the spring aside on a clean towel (if your going to re-use it) or replacing the spring with aftermarket HD springs. now dump the remaining oil into the bucket or large pan, also what your going to want to do is Pump or (compress) the fork to extract the oil out continue till all oil is out.

Step 8: now fill the the tube with fork fluid (fork oil) I recomend 20wt and 100mm +/-2mm of air gap with the spring out (this is going to be anywhere from 3.5 ounces to 5.5 ounces depending on the forks) so start out with the lower amount and work you way up till you get the air gap. Do this with the fork tube compressed. Once you get the proper level and its set, slowly pump the fork tube to get the air bubbles out. once all the bubbles are out re-measure the air gap and if more fluid is needed do it now

Step 9: now extend the fork tube and slowly drop in the old or (new HD Spring). when the spring is in re-install the fork cap being very carefull not to compress the fork tube and spilling out the fork oil.

Step 10: Re-install the fork up into the fork clamps do not over tighten the bolts or pinch bolts ( 8-10 ftlbs of torque). also tighten the top nut cap once the tubes of the fork are tight in the clamps do not over tighten the fork cap!!!

Step 11: Repeat steps 5 through 10 to the right side fork tube

Step 12: put your front wheel back on make sure the spacers are on the correct side and torque the axle nut to 32ft lbs. put the brake caliper on the fork leg if you have disc set-up and or reconnect the front brake cable up to the brake lever.


Note: the Air Gap is the measurement from where the fork fluid level sits inside the fork tube in reference to the top of the fork tube. the distance between these two is the air gap

_________________
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http://www.pitsterpro.com


02 Jan 2009, 16:04
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Joined: 06 Jan 2009, 18:08
Posts: 56
Post Re: Fork tuning and set up
my rear suspension does not move, its all stock im the original owner, ive got the preload all the way out, well untill it starts to fall away, its rock hard i push it down and it moves half an inch


06 Jan 2009, 18:33
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Site Admin

Joined: 12 Sep 2008, 14:04
Posts: 326
Post Re: Fork tuning and set up
monaghan wrote:
my rear suspension does not move, its all stock im the original owner, ive got the preload all the way out, well untill it starts to fall away, its rock hard i push it down and it moves half an inch



What is the bike you have and what is your weight, what settings to you have the comp and reb set at?

_________________
Pitster Pro Pit Bikes
http://www.pitsterpro.com


07 Jan 2009, 15:31
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Joined: 06 Jan 2009, 18:08
Posts: 56
Post Re: Fork tuning and set up
admin wrote:
monaghan wrote:
my rear suspension does not move, its all stock im the original owner, ive got the preload all the way out, well untill it starts to fall away, its rock hard i push it down and it moves half an inch



What is the bike you have and what is your weight, what settings to you have the comp and reb set at?

i know how to tune my suspension ive been doing it for a while. the comp. nob doesnt make a difference and the rebound knob doesnt work


13 Feb 2009, 15:16
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Joined: 22 Nov 2008, 09:40
Posts: 16
Post Re: Fork tuning and set up
what model bike?? sounds like the compression might be stuck internally?


14 Feb 2009, 21:58
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Joined: 06 Jan 2009, 18:08
Posts: 56
Post Re: Fork tuning and set up
its a 2008 pitster pro x2


18 Feb 2009, 17:26
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Site Admin

Joined: 12 Sep 2008, 14:04
Posts: 326
Post Re: Fork tuning and set up
monaghan wrote:
its a 2008 pitster pro x2

If you want to send in your legs, we are more then happy to take a look at them.

_________________
Pitster Pro Pit Bikes
http://www.pitsterpro.com


05 Mar 2009, 13:27
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