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Discussion Starter #1 (Edited)
I have a 2009 KLR-650. I'm upgrading my front end. I'm new to working on bikes in general and so I'm totally new to front fork work. I've been searching the forums for info on what weight fork oil to use when I install a new set of progressive front fork springs, that I just got in the mail, in a few days.

My bike is setup with Happy Trail Teton panniers, and a 45 liter Givi trunk box. and I'm hoping to do some good longish distance adventure rides this summer across the NW and up to Canada a bit. Today, I was testing some heated gear out on the superslab, and man the front end definitely is squirrely - especially around 70 mph in the stock configuration it's in now - and of course when coming up on and passing semis too. I'm hoping these progressive fork spring, fork oil change out, and fork brace mods will combine to help improve things - for the highway stability at least.

I weigh 220 lbs, and I ride a variety of - long distance highways and superslab (50%); dirt single track trails at the ORV park (20%), and logging roads (30%). I'm hoping to get some help on:

1) OIL WEIGHT - Which oils weights to consider and what they would do

2) OIL VOLUME - how much oil volume to put into my forks and how best to install it - I'm assuming from other posts, I will empty the stock oil out, and with the springs out - compress the fork before replacing with oil. Do I have to take the fork off the bike?

3) OIL MEASUREMENT and ADJUSTMENT - The best ways to measure the oil / remove what is not needed / get the oil equal. Do I need to buy a turkey baster?

4) SPACER LENGTH - How much spacer to use

5) PRE-LOAD RECOMMENDATIONS - What pre-load is recommended.

I'm not going to be spending any additional money on emulators or other fork parts. I do have a EM fork brace coming though, and I'm hoping the combo of oil, new progressive springs, and the brace will setup the front end pretty well.

Thanks much for any help you guys!

Bill

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UPDATE: Images of the change out. I could not have completed these changes without all the help in the posts below from this group! Thanks much everyone!



More fork spring change out images here:
http://www.flickr.com/photos/[email protected]/sets/72157626122567129/
 

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Oy, oy , oy....

The short answer is do what works for you.

Hope that helps...:)

But it really is the right answer.

What you have there are damper rod forks. They pump oil through a set of orifices - using the same orifices for both compression and rebound. There is no adjust-ability, really, beyond swapping the oil out.

I can't give you specific recommendations as mine have been rebuilt with emulators as well as the progressive springs and I have MotoWizard preload adjusters installed.

Let's take things in the order you asked:

Oil weight:


Don't go too heavy. Remember that your forks use the same orifices for compression and rebound. If you use too heavy an oil the springs will not be able to push the forks to rebound quickly, so they will be dead feeling and 'packed up'. You might want to start with ATF, as it is (IIRC) about 7.5 weight. Run it and see how it feels. It's cheaper than fork-specific oils and just about the same stuff. If you install stiffer springs and therefore need more damping, you're going to have to use a thicker oil. That will slow down the compression of the forks, making them stiffer still. If you install softer springs and want less damping to go with them, you need a thinner oil. Of course, the thinner oil will speed up the compression. That's the nature of damping rod forks and this is what emulators fix.

Oil volume:

You don't need to take the forks off of the bike. Start with the stock oil volume and see how it feels. The air in your forks acts like a spring. The more oil, the less air, and the harder the air spring will be. Less oil provides more air for a softer air spring. This is some tune-ability you can take advantage of. If you get your oil and springs working together but want just a tad softer feel/ride, remove some oil. That will reduce the over all spring rate of the forks.

Oil Measurement and Adjustment:


A turkey baster and some aquarium hose is the cheapest tool you can make for this, and it works. You can even buy the cheapest turkey baster you can find.

Spacer length/Preload:

Kinda the same question. Which springs did you get? I seem to recall that there are progressive springs that are the same length as the stock springs and there are some that are quite a bit longer. Were there manufacturer's recommendations? The preload needs to give you the right sag. Shoot for using about 1/3 your suspension travel in static sag. You said you were having problems with the front end hunting. You might want to try a tad bit more preload than you have now and see if that helps it.

Along those lines, the Gen2 bikes have a front fender that is as big as all outdoors. Get rid of it in favor of a 'tard fender. Much of your front end woes may very well be due to that front fender. My bike has a Cycra fender on it. Lockjaw has an Acerbis, Tomatocity runs a KTM, I think. All would be suitable and none would be much more than $25.

T
 

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Discussion Starter #3
Thanks Tom,

I just added one of these lower profile fenders to my list of coming parts for the front end improvements:
http://store.cycraracing.com/fasufrfeb1.html

I'll start out with the ATF then - and a turkey baster and some tubing too to suck out the old oil. I'll measure the volume level before I remove the old stuff. Or maybe I'll put the old stuff in something that I can measure, and put an equal amount of new ATF back in.

The new springs I got from Happy Trails - they are Progressive Suspension front fork springs part 11-1506 - for KLR-650, the box has some 3 inch sched 80 pvc spacers in it. Papers inside say to use the 3" of spacer for the 2008 model KLR-650.

Turkey baster and tubing next? Sounds a bit odd - does it not? Ha
 

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Adventure-Moto -

Measure the height before you take it out. The easiest way to take it out is to pop the Allen head screw on the bottom of the forks and let it drain out.



Remove the Allen bolt from the bottom of the fork leg. This should come out easily. If it doesn't, then you're going to need to stuff an appropriate tool down the fork leg in order to hold the damper tube stationary.
 

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Discussion Starter #5
Thanks again Tom,
Why do I need to hold the damper tube stationary - is it in order to allow the allen head screw to turn out?

Once it is out - and the oil is drained, assuming I can remove the allen head screw at the bottom - do I have to worry about getting the allen screw back in, or maybe when I took it out - releasing anything important on the other side of the screw?

Thanks much for the great help!

AM
 

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Adventure-Moto, you're hep about measuring the HEIGHT of the oil surface to determine volume, and to equalize the amount in the forks, right?

Didn't think the technique had been mentioned on the thread so far.

DO NOT TRY THIS AT HOME, my dealership has a vacuum pump and graduated hose . . . they stick he hose down the fork tube to the desired "height" and then evacuate the excess oil 'til the desired level is obtained. The reason I say forget it at home; few "shade-tree" mechanics could afford/justify such a device!
 

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Discussion Starter #7 (Edited)
Thanks Damocles for the help on fork oil volume determination. I also read in another thread that you need to cycle the fork a few times if it was drained, when you refill it, to make sure you get all the air out of the system.

So for a 2008 Model KL-650, fork fluid change out, and new Progressive spring installation, does this checklist sound right:

A) With the bike level and front fork tubes top main nuts, and stock fork springs removed, measure and record the volume from the top of the tube to the top of the oil level in the tube.

B) Drain the fork oil in both tubes, via the center hex bolt Tom refers to above, at the bottom of the fork assembly. (( do I Cycle the fork assembly to get all the oil out? ))

C) Replace the hex bolt used to drain the fork at the bottom of the fork tubes.

D) Install the new fork oil, to the same height as the "stock fork oil level" recorded earlier. (( ?? Be sure to cycle the fork assembly to get the air out when replacing fork oil ?? ))

E) Install the new Progressive front fork springs, and the 3" spacers on top of them.

F) Replace the fork top main nuts, and torque to (( I will look the torque value up in the clymer manual ))

G) Tighten the fork tube bolts to required ((I will look up the value)) torque value.
 

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A-M -

That sounds about right.

The bolt in the bottom of the fork holds the damper rod in place. I was able to both remove and install the bolt with no problem, but there is a chance that the rod could spin. If that happens you need to fab up some sort of a tool to hold the rod in place as you tighten the screw. It need not be anything elaborate; a hunk of 1/2" dowel, three feet long, will do. Here's a picture of the damper rod:



T
 

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Adventure-Moto, you're hep about measuring the HEIGHT of the oil surface to determine volume, and to equalize the amount in the forks, right?

Didn't think the technique had been mentioned on the thread so far.

DO NOT TRY THIS AT HOME, my dealership has a vacuum pump and graduated hose . . . they stick he hose down the fork tube to the desired "height" and then evacuate the excess oil 'til the desired level is obtained. The reason I say forget it at home; few "shade-tree" mechanics could afford/justify such a device!
.....

...

Oil Measurement and Adjustment:


A turkey baster and some aquarium hose is the cheapest tool you can make for this, and it works. You can even buy the cheapest turkey baster you can find.
...

Turkey basters are about $2. Some aquarium hose and a sharpie to mark the level completes the set-up.

T
 

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Thanks Damocles for the help on fork oil volume determination. I also read in another thread that you need to cycle the fork a few times if it was drained, when you refill it, to make sure you get all the air out of the system.

So for a 2008 Model KL-650, fork fluid change out, and new Progressive spring installation, does this checklist sound right:

A) With the bike level and front fork tubes top main nuts, and stock fork springs removed, measure and record the volume from the top of the tube to the top of the oil level in the tube.

B) Drain the fork oil in both tubes, via the center hex bolt Tom refers to above, at the bottom of the fork assembly. (( do I Cycle the fork assembly to get all the oil out? ))

C) Replace the hex bolt used to drain the fork at the bottom of the fork tubes.

D) Install the new fork oil, to the same height as the "stock fork oil level" recorded earlier. (( ?? Be sure to cycle the fork assembly to get the air out when replacing fork oil ?? ))

E) Install the new Progressive front fork springs, and the 3" spacers on top of them.

F) Replace the fork top main nuts, and torque to (( I will look the torque value up in the clymer manual ))

G) Tighten the fork tube bolts to required ((I will look up the value)) torque value.

I wouldn't try to take the springs out with the forks on the bike, you'll get oil everywhere. The only thing I would do with the forks on the bike is loosen the top cap (with the top triple clamp bolts loose of course).

I also wouldn't try to loosen the bottom bolt unless you want to pull the damper rod out. Chances are it will spin and you will have to have a tool to hold the rod. BTW you can usually use a length of PVC with a slot cut into it.

Here's how I do it:

1. Top triple clamp bolts loose, loosen fork caps.
2. Remove forks
3. Remove fork caps and springs, turn forks upside down and let them drain for awhile. Pump the forks to get all the oil out.
4. Fill with Mobile 1 ATF. Height is personal preference I would go with the stock height as you're changing springs and go from there.
5. I use a large syringe type thing with some clear tubing marked for height. Basically you overfill a bit and suck the oil down to the level.
6. Replace springs and spacers and start top cap.
7. Replace forks, tighten lower tripple clamp, tighten top cap and upper clamp.
 

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Discussion Starter #12 (Edited)
Installed my new springs tonight - pics

The pics show the removal of the forks top nut, then the removal of the stock spacer, washer and spring. I measured the oil as best I could, and then added a bit, and sucked up the same amount on each side using the tool described below. I did not drain it or change the oil out. I only have 1000 miles on the bike right now, so I think the oil is okay. I stayed with the stock 2009 KLR-650 fork oil of 10 weight.

TWO NOTES:

1) OIL LEVEL ADJUSTMENTS: ((Thanks for the help on this part from Damocles, Tom and Spec!)) - To get the oil level the same in both sides you can, "suck it down" to a predetermined height, by making a "oil leveling suck down tool" out of a thing like a turkey baster, and some tubing. If you cut the tubing at the same height you want your oil fork oil levels to be at, then you can overfill both tubes a bit, and then use your oil leveling tool, to suck up the excess, until you get it all up, and start sucking up air - leaving the correct amount in your fork tubes. The level in the Clymer manual says around 5.3 inches when the tubes are fully compressed. So that's what I set my tube oil height to be at.

2) WATCH OUT IF WORKING WITHOUT A MOTORCYCLE LIFT / JACK: When I was compressing my front tubes with the springs out, so that I could measure and adjust the fork oil levels, I rocked the bike too far forward off the center stand and the bike came off the center stand. This compressed the tubes nicely, and allowed me to work on the tube levels, but it made it very hard to hold the bike steady. Even worse, once I got the tubes oil levels right, I had to get a friend to help out to get it back on it's center stand, so that I could get the tubes extended again, and could put the new springs and spacers in. He had to help out by picking up the back of the bike to get the center stand back under her. I darn sure wish I had a motorcycle lift / jack. I'm definitely buying one soon... ha!


I'll put the Eagle Mike fork brace and new front fender on tomorrow.

Progressive spring install pics showing the taking of the the stock parts out - and so, the install is the reverse process.

http://www.flickr.com/photos/[email protected]/sets/72157626122567129/

Enjoy! And again, thanks much to this great group for all the help on this mod!

AM

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UPDATE: One of the big reasons I wanted to try these new springs, was to stabilize and stiffen up a bit, the front end. I also placed an eagle mike fork brace on, and did a front fender change out to a smaller surface area front fender, that you can read about in this link:
http://www.klrforum.com/showthread.php?t=10318
All three of these mods; springs, brace and fender, have helped stabilize and plant the front end now when I'm traveling at highway speeds.

AM
 

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Adventure-Moto,

Nicely done!

I had to laugh, though. I remember fishing my fork guts out with a magnetic probe. I'd stick it down the tube and CLANK!, it would latch itself to the side of the tube. CLANK, CLANK, CLANK! It was worse trying to put stuff back in. I was too dumb to go get a coat hanger...

Heavy sigh.

T
 

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Discussion Starter #14
Thanks Tom!

Never a dull moment with these contraptions eh? haha.

Hey, what do you guys think about the level of precision needed on matching the fork oil heights in each fork? For example, if one fork was off say a half inch or a quarter inch from the other - would it play havoc or not be noticed?

Thanks again for the great help you guys!
 

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I would think that level of mis-match would not be noted.

However, comma, but.... It would seem well within ease to get them to match within an eighth of an inch even with a turkey baster type thingamajig.

T
 

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Discussion Starter #16 (Edited)
That makes sense to me Tom,

I don't know myself - but just thinking about the part that is different, and that does compress - which would be the volume of air in each tube, and what ever that air differential in each tube would be what causes the different fork action I am assuming.

So there would not be much difference in terms of each tubes air volume, with each side having the incompressible though uneven oil part, and then the different air volumes would be pretty darn small with being only a quarter inch or even a half inch off - out of 5.3 inches in a fully compressed tube - and much more than that in a fully extended tube.

So it seems reasonable that there would not be a noticeable big difference. But I know I'm no expert! Non-the-less as you stated, getting it as close to the same in each fork is my goal.

Most of the fork action is gonna come from the springs I assume, and the oil moving though the orifices? Is that correct?
 

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...

Most of the fork action is gonna come from the springs I assume, and the oil moving though the orifices? Is that correct?

Suspension springs support the weight of the bike and rider. The actual suspension action is mostly controlled by hydraulics, oil moving through orifices/shims. The springs do have some effect, mostly in rebound.

Pre-load is adjusting the springs for the rider's weight and gear. The hydraulic action is set for a certain range and rate of motion. That's why it's important to have the pre-load correct. That's also why springs come in varying weights (rates).

More info you probably don't want to read... the KLR's forks uses old tech damper rods. They have graduated sized holes that force the oil through to control compression and rebound. Accordingly they compromise the various stages of travel to achieve an overall effect. Typically the initial motion will be soft but bigger hits will be harsh. Progressive springs try to firm up the initial movement but still allow the midrange to react well. The various replacement valving products (gold valves, etc.) are trying to do the same thing by controlling the oil flow better than the damper rod's holes (which are drilled out allowing the devices to control the hydraulic action).
 

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Most of the fork action is gonna come from the springs I assume, and the oil moving though the orifices? Is that correct?
Spec's right - the springs support the bike and rider.

It get's simple if you think of it this way - imagine that there is no hydraulic fluid in the forks. Would they still work? Yes, they would. The bike sould be supported, and when you went over a bump they would absorb the impact. But how well would they work? What would they do? If you impact a spring it absorbs energy. It then continues to oscillate until the energy is dissapated. Your forks would act that way, too. You'd be bouncing all over the road.

What the hydraulic fluid does is dampen the spring, and it does that by forcing fluid through relatively small holes. The holes provide resistance, and the energy in the spring is dampened by converting it to heat. The Dampening Rod Fork design has but one set of holes that the fluid passes through on both compression and rebound. As such, they aren't very tunable, but they are cheap!

T
 
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