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Author Topic: How to internally lower your forks. Updated with better pics. 6/20/09  (Read 199006 times)

Offline spdingtkts

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #100 on: January 13, 2010, 01:08:10 PM »
Here is a good kit to get you started in the right direction here -

http://traxxionstore.com/detail-12.aspx



I've yet to see a decent JE piston.  All the ones that have come through my door are big heavy clunky items.

Offline Coryonbusa

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #101 on: January 13, 2010, 06:00:06 PM »
He is a hater  :finger:
No, a mechanic.

You can see how chewed up the damping rod got in the close up pic. How is that going to work with the coated bushing in the cartridge head?

Do you really think grabbing those soft aluminum parts with pipe wrenches is the right way or a good way to that?

Do you think the cylinder is still round where the pipe wrench clamped down on it?

You are reducing the travel to pretty much the very bottom of its range. The hydraulic anti-bottoming out piston kicks in around there which pretty much locks up the fork making it harsh. Why don't you do anything with that? There are some good options out there.

What is the amount of spring preload now that you cut the spacer?

The stock spring rate is 8.5 on the 99 to 07 which is way too light for that bike. The 08 and up uses a  9.3 which is still on the light side. Wouldn't you want to change the springs to help keep the bike from bottoming?

I am guessing that you have no idea about the shim stack so you throw in some really thick oil. Not the best solution IMO. Then you just dump in xx amount with no idea of what the oil height is. The oil height is considered an air spring that acts progressively. Too high the forks will feel stiff. There is no way you are bleeding all the air out with your four pump chump method either.

The spacer looks like conduit cut with a hack saw. You ever hear of a tubing cutter or God forbid use a lathe to make some nice spacers?

I know its the cheap way so that makes it great to some of you but come on. Is there anyone out there that is going to tell me that this is the correct way to work on these forks?

Would you grab your crankshaft or camshaft with a pipe wrench?




Alright! See, now that's a good post! :thumb:
Lot's of good points and suggestions in there. :thumb:
No need to hate on me or anyone for trying to save someone $200.oo+ on having their forks cut.

I guess I could change the first post to say that if you have the money, have your forks done professionally. If not, here's a cheap way that will work. I dont work on bikes professionally and I dont know it all. I wrote this article with the help of a few others that have built forks for some pretty quick bikes. :thumb:

Addressing yor concerns:

You can see how chewed up the damping rod got in the close up pic. How is that going to work with the coated bushing in the cartridge head?

Do you really think grabbing those soft aluminum parts with pipe wrenches is the right way or a good way to that?

Do you think the cylinder is still round where the pipe wrench clamped down on it?

Pipe wrenches will scar up aluminium. It will not crush the pipes because pipe wreches dont work that way. They grip only enough to hold. Where you hold on to the rod will be under the lowering spacer and will not travel through the bushing.

You are reducing the travel to pretty much the very bottom of its range. The hydraulic anti-bottoming out piston kicks in around there which pretty much locks up the fork making it harsh. Why don't you do anything with that? There are some good options out there.

I'm not %100 sure what you're talking about. The cut fork should bottom out the same as an uncut fork?



What is the amount of spring preload now that you cut the spacer?

The preload will be the same, if you remove the same amount of the lowering spacer from the stock spacer. :thumb:

The stock spring rate is 8.5 on the 99 to 07 which is way too light for that bike. The 08 and up uses a  9.3 which is still on the light side. Wouldn't you want to change the springs to help keep the bike from bottoming?

Yeah, the stock springs are light. Adding a heavy spring, especially for us big guys, is not a bad idea. :thumb:
You can accomplish close to the same result by adding more preload. Though you can't add too much preload or you'll bind up the spring...
 
I am guessing that you have no idea about the shim stack so you throw in some really thick oil. Not the best solution IMO. Then you just dump in xx amount with no idea of what the oil height is. The oil height is considered an air spring that acts progressively. Too high the forks will feel stiff. There is no way you are bleeding all the air out with your four pump chump method either.

You are correct on the shim stack or oil height, I have not idea what you're talking about. :D If you want to share some knowledge, please do! As far as bleeding the air, what do you suggest? This way seem to work well for me and countless others. :thumb:

The spacer looks like conduit cut with a hack saw. You ever hear of a tubing cutter or God forbid use a lathe to make some nice spacers?

What can I say? When you're working in a hot garage, you'll do anything to get it done! :lol: If you'll notice the 2"ers we took out were machined sleeves that I put in there the first time...

Offline Rice Ya

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #102 on: January 13, 2010, 06:50:35 PM »
Made my own fork tools for free. :wink:
Untill you give it everything you've got, you won't know if you got what it takes. Dave Schultz

Offline sportbikeryder

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #103 on: January 13, 2010, 07:02:35 PM »
I agree that using more suitable tools, machined spacers, and replacing the shim stack may make for a nicer job, however, someone wanting suspension capable of providing better damping than stock likely would not be in trying to lower them and reduce travel at all. This mod is intended for dragracing (or I supose for posers with wide tire kits who don't need better suspensions anyway) and not for applications requiring a great deal of suspension energy dissapation.

It could be done in better ways, however for this application, this method will produce the same ET as a more expensive solution.

Kent Stotz performed quite well in streetbike shootout. Ever look at his bikes? Stock extended swingarm, cut off and re-welded footpeg mounts to make "rearsets", not the most mainstream or pretty applications, however, they function just fine.
 
Hundreds of Hayabusa's run an intake cam on the exhaust side, even though the lobe spacing is "wrong" and is an "improper" way to build an engine.

Ever design a chain drive? Motorcycle chain drives violate general design practices by an order of magnitude or more with respect to countershaft pitch diameter for the torque they transmit.

Removing the countershaft and transmission input shaft nut with an impact is "improper" as well....

« Last Edit: January 13, 2010, 07:06:42 PM by sportbikeryder »
Any day on a motorcycle like this that ends just needing parts and labor is a good day.
4.82, 158.67mph 1/8th mile 7.350, 200.32mph 1/4 mile Riding

4.392, 176.79mph 1/8th mile  6.610, 228.15mph 1/4 mile Tuning

Offline sportbikeryder

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #104 on: January 13, 2010, 07:08:17 PM »
Here is a good kit to get you started in the right direction here -

http://traxxionstore.com/detail-12.aspx





Is there a tool in there that eliminates the pipe wrenches?
Any day on a motorcycle like this that ends just needing parts and labor is a good day.
4.82, 158.67mph 1/8th mile 7.350, 200.32mph 1/4 mile Riding

4.392, 176.79mph 1/8th mile  6.610, 228.15mph 1/4 mile Tuning

Offline TrickTom1

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #105 on: January 13, 2010, 08:09:37 PM »
I posted this around on a few boards and people are really laughing at you idiots.

I guarantee if any of you stepped up and set your forks out to a suspension shop to have the length shortened the difference between the workmanship and the quality of the ride.

This site has really gone downhill since I first joined it years ago.
go back to your other websites then  :thumb:
« Last Edit: January 14, 2010, 05:57:29 AM by TrickTom1 »

Offline spdingtkts

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #106 on: January 13, 2010, 08:40:44 PM »
I guess I could change the first post to say that if you have the money, have your forks done professionally. If not, here's a cheap way that will work. I dont work on bikes professionally and I dont know it all. I wrote this article with the help of a few others that have built forks for some pretty quick bikes. :thumb:

There is a right way and a wrong way and any way that damages parts is the wrong way.

Pipe wrenches will scar up aluminium. It will not crush the pipes because pipe wreches dont work that way. They grip only enough to hold. Where you hold on to the rod will be under the lowering spacer and will not travel through the bushing.

I own and have used pipe wrenches (but not on fork internals). I have also disassembled the cartridges so I am very familiar with the amount of force required to remove the cartridge head from the cylinder. Kayaba uses some type of epoxy on them as residue on the threads is white. Trust me, if you were to run a bore gauge through the sections of the cylinder where you grabbed it with the pipe wrench you will see it is no longer round.

While you are correct that the marred up end of the damping rod will not come in contact with the bushing in the cartridge head while the spacer is there what happens if you have to put it back to stock?

It would be one thing if there was no other way to do it, but Race Tech sells a shaft holding tool for that purpose. They also sell a cartridge holding tool for cartridge disassembly so that you do not damage the cylinder.

I'm not %100 sure what you're talking about. The cut fork should bottom out the same as an uncut fork?

They bottom out the same but you have reduced the range of travel. About half the time that fork is moving it is much harsher than it needs to be. There a couple of options to change this. There are two methods that are free and will improve the forks function. There is another option that requires you buy some parts, but IMO offers a much better solution.

The preload will be the same, if you remove the same amount of the lowering spacer from the stock spacer. :thumb:

OK then, what is the base preload on a stock set of forks?

When you set up a set of forks you install the springs with a base preload on the springs, usually 10 or 15 mm (unless you are working with Ohlins stuff).

Yeah, the stock springs are light. Adding a heavy spring, especially for us big guys, is not a bad idea. :thumb:
You can accomplish close to the same result by adding more preload. Though you can't add too much preload or you'll bind up the spring...

You shouldn't be binding the spring up. If you are worried about binding up the spring then I would suggest running a stiffer rate spring than you would normally run but installing it with less base preload.

You are correct on the shim stack or oil height, I have not idea what you're talking about. :D If you want to share some knowledge, please do! As far as bleeding the air, what do you suggest? This way seem to work well for me and countless others. :thumb:

To bleed the cartridge you want to install the cartridge (using a different type of cartridge holding tool to hold the cartridge while you torque it) with the damping rod installed and no spring. I open up the compression adjuster all the way and pour some fork oil in, usually about 150mm from the top of the outer fork tube. I work the damping rod up and down several times and then let drop in all the way. I then extend the fork a little longer than its normal fully extended length, put my hand tightly over the top to seal it and then push down on the fork. This pushes the oil through the cartridge. Once I do that several times I then install a bleeder tool on the damping rod and work it up and down until I no longer see any air bubbles. It takes a long time to bleed the air out.

I then use a fork oil height tool to set the height as this is something you can tune with. Oil height is dependent on what type of valving you are running and somewhat of a personal preference. Depending on the set up and the rider's class I usually start a new rider out with 130mm to 120mm and then experiment from there.

Remember, the space left in the fork by the oil acts as a progressive spring. The higher the oil level, the stiffer it gets as the fork compresses.

Also, that Bel-Ray 20wt fork oil is thick as hell. They run that damper rod forks.
 
What can I say? When you're working in a hot garage, you'll do anything to get it done! :lol: If you'll notice the 2"ers we took out were machined sleeves that I put in there the first time...

Metal on metal wear creates particles that contaminates the oil which wears the valve faces and shims.

Personally I would machine up spacers made of Delrin and install them with a washer at the spring end. And if anyone thinks the Delrin is no good, Ohlins uses Delrin spacers to adjust fork length in all of their Superbike, new style R&T forks, and Superbike Cartridges.

I know that you are not going for handling when doing this mod, but you can make changes to so that it improves the ride quality. I can only imagine how rough that front end feels. In the end you want the forks to move as smoothly as possible. If you look at the forks you will see other things that need to be addressed to make them work correctly.

You want everything super clean as you do not want to contaminate the oil.

These guys here -

http://www.dirtrider.com/tech/141_0806_race_tech_fork_rebuild_secrets/index.html

are servicing a set of dirbike forks. While Busa forks do not have all the parts they have, you can see some of the tools they and methods they are using.
« Last Edit: January 14, 2010, 08:06:47 AM by spdingtkts »
I've yet to see a decent JE piston.  All the ones that have come through my door are big heavy clunky items.

Offline spdingtkts

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #107 on: January 13, 2010, 09:12:39 PM »
Is there a tool in there that eliminates the pipe wrenches?
Not in that set up, but look at the tools used in the link I posted in my thread before this one.

Also -

Tool for holding cartridge in place so you can torque the bolt at the bottom.
http://www.racetech.com/HTML_FILES/CARTRIDGE_HOLDING.html

Shaft and cartridge holding vise adapters (these are the tools that eliminate the pipe wrenches).
http://www.racetech.com/HTML_FILES/SHAFT_HOLDING.html
I've yet to see a decent JE piston.  All the ones that have come through my door are big heavy clunky items.

Offline sportbikeryder

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #108 on: January 13, 2010, 09:27:21 PM »
http://www.dirtrider.com/tech/141_0806_race_tech_fork_rebuild_secrets/photo_14.html

Really?....Really? Grinding or filing on the parts?


How about using a lathe to turn the mushroomed portion off and then remove the nut. Jeeze....Racetech must be a bunch of idiots.... :lol:
Any day on a motorcycle like this that ends just needing parts and labor is a good day.
4.82, 158.67mph 1/8th mile 7.350, 200.32mph 1/4 mile Riding

4.392, 176.79mph 1/8th mile  6.610, 228.15mph 1/4 mile Tuning

Offline Coryonbusa

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #109 on: January 14, 2010, 05:09:02 AM »
Good post spdingtkts. :thumb:

Your points are valid and I hope that someone finds it usefull.

Offline spdingtkts

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #110 on: January 14, 2010, 08:14:59 AM »
The stock spring rate is 8.5 on the 99 to 07 which is way too light for that bike. The 08 and up uses a  9.3 which is still on the light side. Wouldn't you want to change the springs to help keep the bike from bottoming?

Yeah, the stock springs are light. Adding a heavy spring, especially for us big guys, is not a bad idea. :thumb:
You can accomplish close to the same result by adding more preload. Though you can't add too much preload or you'll bind up the spring...

When I first read this I originally thought by adding more preload you were talking about via the adjuster at the top.

Then I thought about your statement about coil binding the spring so it occurred to me that you are talking about leaving the spring preload spacer long to provide more base preload to compensate for an incorrect spring rate.

You do not want to that. If you preload the spring too much it will not work like it is supposed to and I am not just talking about coil bind issues.

« Last Edit: January 14, 2010, 09:54:33 AM by spdingtkts »
I've yet to see a decent JE piston.  All the ones that have come through my door are big heavy clunky items.

Offline mike46

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #111 on: January 15, 2010, 10:27:43 PM »
Cory is the God of the Fork! :mrgreen:
Using pipe wrenches?

While his technical info is current his workmanship reminds me of the saying "Not all butchers work with meat."

did you mean "not all butchers work with knives"?

because you're trying to take a jab at his tool selection,  not what he is working on...

 "not all self proclaimed geniuses work with their brains" eh Mr speedingdckless?
  Apparently not all chooch's live in barns Sparky. Tkts is a big Glock fan too....you minga fach. :lol: He answered questions.
« Last Edit: January 15, 2010, 10:32:19 PM by mike46 »
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Offline SPARKY1397R

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #112 on: January 16, 2010, 05:18:13 PM »
you should come hang out at work with me mike,  i'm sure you'd have a blast. 

Offline Coryonbusa

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #113 on: January 16, 2010, 06:09:03 PM »
you should come hang out at work with me mike,  i'm sure you'd have a blast. 

:lol:

Offline mike46

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #114 on: January 17, 2010, 10:09:38 AM »
you should come hang out at work with me mike,  i'm sure you'd have a blast. 
I believe I would. :wink:
" The inherent vice of capitalism is the unequal sharing of blessing, the inherent virtue of socialism is the equal sharing of miseries"  Winston Churchill. Obviously Obama is no student of history.

Offline nickelcityracing

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #115 on: January 31, 2010, 07:48:24 AM »
I posted this around on a few boards and people are really laughing at you idiots.

I guarantee if any of you stepped up and set your forks out to a suspension shop to have the length shortened the difference between the workmanship and the quality of the ride.

This site has really gone downhill since I first joined it years ago.
go back to your other websites then  :thumb:
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Offline TrickTom1

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #116 on: August 21, 2010, 09:48:50 PM »
 :D

Offline Coryonbusa

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #117 on: August 22, 2010, 07:04:19 AM »
It is funny to read it all again. :lol:

Offline Mike-Nightrider

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #118 on: August 24, 2010, 02:59:03 PM »
It is funny to read it all again. :lol:

 :thumb:  :D
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Offline murderedout07

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #119 on: December 14, 2010, 11:57:01 AM »
So did anyone figure out some off the shelf spacers you could use, As far O.D. and I.D.?

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Offline boofoo

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #120 on: December 14, 2010, 05:33:38 PM »
So did anyone figure out some off the shelf spacers you could use, As far O.D. and I.D.?
Looked like conduit in the first pic's. Could just take a pair of calipers to a supply place and check.
Or
http://www.schnitzracingstore.com/catalogs/catalog.asp?prodid=2704270&showprevnext=1

Offline BUSA750

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #121 on: March 18, 2011, 04:53:04 PM »
So did anyone figure out some off the shelf spacers you could use, As far O.D. and I.D.?


what od and id are u looking for

Offline spdingtkts

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #122 on: March 26, 2011, 09:07:59 PM »
Looked like conduit in the first pic's. Could just take a pair of calipers to a supply place and check.
DO NOT use conduit or PVC pipe. It cracks and breaks apart over time and that can cause BIG problems.
I've yet to see a decent JE piston.  All the ones that have come through my door are big heavy clunky items.

Offline kscampbell08

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #123 on: June 08, 2012, 11:13:52 AM »
Wanna say great post thanks for the help, but i have a question tried this on my 02 gsxr 750 forks apear to be different internally could not get lower tube off? any help? thanks

Offline ChopperCharles

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Re: How to internally lower your forks. Updated with better pics. 6/20/09
« Reply #124 on: June 26, 2012, 06:03:44 PM »
I know I'm resurrecting an old thread, but I have a related question. How do I go about EXTENDING the forks an inch or two? Can I just get a longer allen bolt and put a spacer between the bottom of the cartridge and the bottom of the fork? Building an adventure tourer kind of thing, and need some more ground clearance.

Thanks.

Charles.