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post #1 of 22 (permalink) Old 8-24-2008, 9:27 PM Thread Starter
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Adjusting the front springs

Adjusting the front springs
By: FOG

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The 1st gen bikes enjoy a really long spring 22" if I remember right. This give a lot of room to experiment with diffrent cutting a shimming. For almost free you can tune your forks to suit to perfectly. As you cut (shorten) the spring it's rate(see glossary) goes up.
For most riders over 150 lbs the springs are too soft. start but cutting about 5" off the spring legnth then replacing that legnth with a piece of 1" PVC pipe cut to a legnth that will support the sag at about 1 1/4" Note you may have to cut several spacers to achieve this , but 10 Feet of PVC is only about 3 bucks at Home De Poo.
If that legnth is too soft you can cut more and re shim etc.
AT My home racetrack there were two places that the forks bottomed out even after I got the ride I wanted everywhere else. The controll This I added another short set of springs down inside of the main spring. I used 2 of the innere valve springs in each fork. These springs were operated by a Legnth of 1/2" PVC pipe inside of the 1" cut to a legnth that would just cause them. to come into play near the bottom of fork travel. Thereby adding there rate to the main spring and stiffening the whole thing to prevent bottoming with out making the normal ride too stiff.

BTW this is what the Race Tech Emulators do for 130 bucks or more

Spring rate: is the force required to compress a spring a given amount. straight springs like this are uniform. that's is exactly the same increment will colapse the spring the same amount till the coils are solid. Explanation: if 10 lbs collapses the spring 1" every 10 pounds thereafter will close it another inch, 30 lbs+3"

Have fun and don't be affraid to cut the spring.

FOG


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post #2 of 22 (permalink) Old 11-19-2008, 2:42 PM
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Re: Adjusting the front springs

I think it should be known that the 2nd gen bikes have a shorter spring and should not be cut more then 3"....

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post #3 of 22 (permalink) Old 4-24-2009, 2:41 AM
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Re: Adjusting the front springs

when does 2nd gen start?

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post #4 of 22 (permalink) Old 4-24-2009, 10:51 AM
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Re: Adjusting the front springs

2nd Gen began in 1994.

In
https://www.ex-500.com/index.php/topic,1251.0.html

The poster cut 5" from a '94. 17" spring down to 12" and it came out pretty well. I plan on doing this eventually, along with adding the second inner spring.

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post #5 of 22 (permalink) Old 9-18-2009, 9:04 PM
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Re: Adjusting the front springs

ok so with my 07 ex i should only cut upto 3 inches off so if im 160lbs adding to the bikes 400 lbs would about 2 inches be right and would that also mean 2 inches of pvc pipe for spacing?

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post #6 of 22 (permalink) Old 7-12-2010, 7:27 PM
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Re: Adjusting the front springs

5" of spring cut seems like a lot. Are the stock springs that soft?

And once cut we're talking about an equal length of PVC pipe = 5", yes?

I just acquired a '99 that has been "well loved" and I'm researching to find out what economical options are available for this bike. Front fork oil & seals need replacing. Do the bushings ever need replacing?

I have a Clymer manual in hand.
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post #7 of 22 (permalink) Old 7-16-2010, 1:38 AM
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Re: Adjusting the front springs

Quote:
Originally Posted by SO FUN
5" of spring cut seems like a lot. Are the stock springs that soft?

And once cut we're talking about an equal length of PVC pipe = 5", yes?

I just acquired a '99 that has been "well loved" and I'm researching to find out what economical options are available for this bike. Front fork oil & seals need replacing. Do the bushings ever need replacing?

I have a Clymer manual in hand.
Nice, my first post here & I'm questioning the authorities. DOH! I apologize.

Second, not knowing much about the EX500 I failed to notice my front forks are from a Honda. Dual disc brakes on a 2.5x17 wheel, 37mm forks. I have no information as to what these forks came from. Any advice on finding out what I've got so I can at least get new seals/oil in them?
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post #8 of 22 (permalink) Old 7-16-2010, 8:03 AM
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Re: Adjusting the front springs

Check Sag and act accordingly.

FOG

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post #9 of 22 (permalink) Old 7-16-2010, 1:36 PM
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Re: Adjusting the front springs

Quote:
Originally Posted by SO FUN
Quote:
Originally Posted by SO FUN
5" of spring cut seems like a lot. Are the stock springs that soft?

And once cut we're talking about an equal length of PVC pipe = 5", yes?

I just acquired a '99 that has been "well loved" and I'm researching to find out what economical options are available for this bike. Front fork oil & seals need replacing. Do the bushings ever need replacing?

I have a Clymer manual in hand.
Nice, my first post here & I'm questioning the authorities. DOH! I apologize.

Second, not knowing much about the EX500 I failed to notice my front forks are from a Honda. Dual disc brakes on a 2.5x17 wheel, 37mm forks. I have no information as to what these forks came from. Any advice on finding out what I've got so I can at least get new seals/oil in them?

Im having the same issues...My not so stock 500 may have aftermarket springs but theres no way i can tell. i want to cut them but cant decide if its worth it. I posted pics of them here to trying to see if they looked like anyone elses but no one responded. Ive came the the conclusion that this forum is good for finding general knowledge but some people dont wanna help with specifics, they just tell you to research. (I think no response would be better)

Try posting some pics here, without those you dont have a chance to id them...unless they have some part numbers.

PS> ALWAYS QUESTION THE AUTHORITIES....keeps them on their toes

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post #10 of 22 (permalink) Old 2-26-2011, 10:00 PM
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Re: Adjusting the front springs

I was going to go about making an adjustment to my sag, but the 1" pvc I got is too big. Sure it isn't 3/4" I need for a 2nd gen?


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post #11 of 22 (permalink) Old 7-5-2011, 8:09 PM
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Re: Adjusting the front springs

When I take the forks apart, are there any seals, o-rings, etc or can everything be put back together (assuming that it's not leaking/cracking/whatever). If some things need to be replaced, is there a kit that I can buy with all the stuff, or do they need to be bough individually?

Thanks!!!

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post #12 of 22 (permalink) Old 7-21-2011, 7:52 AM
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Re: Adjusting the front springs

Buy new seals and dust boots...and fluid.you will Pay around $30 for the new parts...for that kind of loot its not worth trying to half ass it and causing more work.

If it floats...flys...or f*cks...its cheaper to rent it.
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post #13 of 22 (permalink) Old 7-21-2011, 8:57 AM
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Re: Adjusting the front springs

Fork seals do not have a finite liketime. They are good untill they are bad. Usually fromm some external damage. IE: new seals won't necessarilly last longer than the ones you have,if they are good, they are good.
A premptive change will do nothing.

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post #14 of 22 (permalink) Old 7-22-2011, 1:58 AM
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Re: Adjusting the front springs

Quote:
Originally Posted by FOG
Fork seals do not have a finite liketime. They are good untill they are bad. Usually fromm some external damage. IE: new seals won't necessarilly last longer than the ones you have,if they are good, they are good.
A premptive change will do nothing.

FOG

i wasnt aware that you can reuse them. thats good to know.

If it floats...flys...or f*cks...its cheaper to rent it.
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post #15 of 22 (permalink) Old 8-13-2011, 12:50 AM
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Re: Adjusting the front springs

If I might add a few thougths here...

There's a little more to it than just shortening your springs. But let's start with that. You can find the formula for determining spring rate here: http://engineersedge.com/spring_comp_calc_k.htm It describes how a spring's stiffness is a function of the material it is made out of, how thick the spring wire is, and how many coils there are in the spring. Don't worry about the math at this point- the important thing is this: a spring's stiffness is inversely related to its length.

So if you cut a spring in half lengthwise, you double its stiffness. Or let's take a simplified, theoretical spring from an EX500 and say that it's 20 inches long, and appropriately stiff for a 125 pound rider. You cut off 5 inches of the spring, making it 3/4 as long as it used to be. What you've got now is a spring that's 4/3 as stiff, or 33% stiffer than the one you started with. So it should be good for a rider who's 33% heavier than 125 pounds, right? Well, no. Don't forget that the springs support the motorcycle as well as the rider. So if the bike weighs, say, 375 pounds and the rider weighs 125 pounds, the bike/rider combination weighs 500 pounds, and the new springs are good for (500 pounds) X (133%) = 665 pounds. Or it would if the front end was supported by only one spring. There are two springs in the fork, each taking up half the work, and the real answer here is that the shortened springs would add only half that extra capacity, or (1/2) X (665-500) = 82.5 more pounds of rider. Which isn't bad if you happen to weigh 207.5 pounds. That's the springs' part of the picture.
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post #16 of 22 (permalink) Old 8-13-2011, 1:19 AM
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Re: Adjusting the front springs

But wait, there's more...

If there were just springs in those fork tubes that would be the end of the discussion. But there's oil in them there tubes. Fork oil is used to damp out the motion of the springs; without it if you hit a bump the springs would compress and rebound repeatedly, and your bike would go wallowing down the road until friction damped out the springs' motion or other inputs from other bumps caused the springs to start boinging along in a different way. This damping is created by forcing the fork oil to flow through small orifices inside the forks. There are different ways of accomplishing this- expensive ones involving shim stacks and adjustable springs and valving, or inexpensive ones like the damper rod fork on the EX500 and most other bikes that come with conventional forks.

The damper rod is basically a long tube with a few holes drilled through it crosswise. As the forks compress, fork oil is forced through these holes in the sides of the damper rod. The end effect is to create resistance to flow, which controls the rate at which the spring can be compressed. Upon rebound, the oil flows back through a different path with smaller passages, creating much more resistance to travel. This rebound damping is what keeps the spring from oscillating and gives you a degree of control. Without adequate damping the wheels tend to thrash around in an uncontrolled fashion, keeping the tires from maintaining good contact with the pavement and giving a rough ride and a bike that tends to drift to the outside of bumpy turns. You can find a good, in-depth description of how a damper rod fork works here: http://www.racetech.com/HTML_FILES/DampingRodForks.HTML

So if you stiffen your springs by shortening them, you'll also need to increase the damping by a similar factor. This is why shortening the springs is only half the job- you need to also change your fork oil. Unfortunately, I don't have any nice easy formula for calculating this. Perhaps someone from the racing community, who has some experience in this area, can expound on this.

One final note on damping. As the velocity of a fluid traveling through a restriction increases, the resistance to flow increases to the fourth power. So if you double the speed of the oil traveling through a damping orifice, the resistance to flow increases sixteen fold. This is the real shortcoming of the damper rod fork. Get your oil thick enough to assure good control and ride quality over reasonably smooth pavement, and you run the risk of hydraulic lock when you hit that square-edged pothole. Thin out your oil so that the forks are compliant over rough stuff and you end up with a wallowy rocking horse of a bike.

What to do? You could install a sort of one-way valve that was spring loaded. Under normal conditions it would stay shut and you wouldn't know it was there, but hit that pothole and the sudden increase in force pops the valve open and bypasses the damper rod, allowing freer compression of the spring and better ride quality and control. Upon rebound it closes, returning the rebound damping duties to the stock internals. That's what a Race Tech Cartridge Emulator does. It has nothing to do with keeping the springs from bottoming. And no, I'm in no way connected with Race Tech, I"ve just had really good results using their Emulators in a couple of SV650s I've owned.
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post #17 of 22 (permalink) Old 8-15-2011, 9:10 AM
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Re: Adjusting the front springs

Trouble is these guys can figure out gas milage or gear ratios. Even with their shoes off.

Around here the instructions have to be like. " Bend tab A Insert into slot 3 then...."

I'm an engineer and I found it easier to just do trial and error. (because you really don't know what you need) It was faster and I got what I needed.
Nice exercise with a calculator though. Maybe there an app.for that on your I pod?
BTW all springs for vehicle use are made from the same stuff with the same Tensil strength. you can toss that part of the calculations.
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post #18 of 22 (permalink) Old 8-15-2011, 11:25 AM
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Re: Adjusting the front springs

... and this is all covered in the WIKI, including how the damper rod vs: cartridge functions. Also mentions the air spring. Also includes sufficient info to determine your own fork spring rate with a bathroom scale. And aftermarket springs usually have the rate engraved in the flat at one of the end faces. Enjoy!

https://www.ex-500.com/index.php/topic,702.0.html

Follow the additional links in the thread to get more.
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post #19 of 22 (permalink) Old 8-22-2011, 11:38 AM
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Re: Adjusting the front springs

Hey do you got some pics or videos
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post #20 of 22 (permalink) Old 6-21-2013, 2:40 PM
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Re: Adjusting the front springs

Quote:
Originally Posted by Rinzler
For most riders over 150 lbs the springs are too soft. start but cutting about 5" off the spring legnth then replacing that legnth with a piece of 1" PVC pipe cut to a legnth that will support the sag at about 1 1/4" Note you may have to cut several spacers to achieve this , but 10 Feet of PVC is only about 3 bucks at Home De Poo.
If that length is too soft you can cut more and re shim etc.
AT My home racetrack there were two places that the forks bottomed out even after I got the ride I wanted everywhere else. The controll This I added another short set of springs down inside of the main spring. I used 2 of the innere valve springs in each fork. These springs were operated by a Legnth of 1/2" PVC pipe inside of the 1" cut to a legnth that would just cause them. to come into play near the bottom of fork travel. Thereby adding there rate to the main spring and stiffening the whole thing to prevent bottoming with out making the normal ride too stiff.
OK. Can we talk about this?? I would love to see a rough drawn pic of what this secondary spring looks like... If someone can explain it to me, maybe I can even draw it up... I just need to understand it first!

Also on this note. I'm around 150 lbs. I'm an amateur rider (<6mo, I learn quick though... I am being cautious!!) I think that my front springs are a bit soft... although, who am I to know! For 160 geared out... should I stick with the stock springs and maybe just up the oil weight a tad? Or is this cut the main spring and add a secondary still a good idea?
My main reason for this is I want better front braking!! I just ordered HH sintered pads to help with this as well...

Please guys, any advice from those more experience is greatly appreciated!!

Thanks!
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post #21 of 22 (permalink) Old 6-21-2013, 7:40 PM
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Re: Adjusting the front springs

Read my first post again.

FOG

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post #22 of 22 (permalink) Old 6-12-2014, 11:45 PM
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Re: Adjusting the front springs

At 195lbs I really need to move this to the top of the list.
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