2005 kdx 220 conversion

Questions and comments about converting to beefier forks..
Malibu406
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Re: 2005 kdx 220 conversion

Post by Malibu406 »

Nothing against professionals, but I enjoy doing it myself as much as riding. Same with old cars.
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Re: 2005 kdx 220 conversion

Post by doakley »

Agree 100%. When I did my conversion I was interested in top results so used a pro tuner who had done this before. I love them!
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Re: 2005 kdx 220 conversion

Post by TwistedRoot »

Malibu: I was wondering how you made out with your setup. Im about to do a rebuild/revalve on my '99s. I wasnt crazy about the handling of the bike after the conversion but I didnt do anything other than pull the forks up in the clamps. They could be much better!
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Re: 2005 kdx 220 conversion

Post by KDXGarage »

replace o-ring with a spring

check the midvalve float

soften the base valve

make sure you have the correct rate springs / good bushings, seals, oil, etc.
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Re: 2005 kdx 220 conversion

Post by Malibu406 »

The conversion fork is stiffer. For slow tifht woods I think the stock forks with heavier springs, oil and shims removed is better. However the conversion is better almost everywhere else. One draw back is they are twitchy at high speed over rocks or flat turns. Im going to remove the seal to bypass the bladder and see if that fixes it.
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Re: 2005 kdx 220 conversion

Post by Malibu406 »

I spent 4 days at Durahmtowm in Georgia. Real nice place to ride unless it rains, the red clay turns as slippery as ice. It started raining and I wrecked twice putting in second gear trying to get back to camp, wow.

Anyway, before I went I removed the white plastic bladder seals and set fork oil at 100 m. Front end a little better and I can run it prety fast in the woods. However there still is the occasional twitchy front end response that is uncomfortable. The best I can describe it is... when pushing in third gear and entering a turn its almost feels like you hit a bunch of marbles causing the handlebar to quickly twitch into the turn. But its not like diving its more like it breaks traction, twitches into the turn BUT pushes straight all at the same time.

I played with compression and rebound settings front and rear. While changes could be noticed, I couldnt eliminate the instability. I’m a little stumped.
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Re: 2005 kdx 220 conversion

Post by doakley »

Hate to say it but one of the most important components to your suspension are tires. Could it be that this is just something that is tire related, either tire choice or wear?
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Re: 2005 kdx 220 conversion

Post by kdxsully »

doakley wrote: 09:50 am Mar 21 2020 Hate to say it but one of the most important components to your suspension are tires. Could it be that this is just something that is tire related, either tire choice or wear?
Probably. In reality, all of these things work together to produce a result greater than the sum of its parts (in my opinion).
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Re: 2005 kdx 220 conversion

Post by javjacob »

Stock KX250 fork springs in my 01 KX250 forks were .43 and went with .40 along with the gold valves and softer settings. I also had them internally lowered 3/4". The KX forks are 1" taller and the RB spacer raises the upper clamp 1/4" so lowering 3/4" is perfect.

When doing a KX fork conversion it is a must to go with softer springs and valving to match the KDX rear end. If you just slap the KX forks on you will be disapointed. The KDX is soft and set up for XC where the KX is stiff and set up for MX. You have to soften the KX forks and set them up for XC.
Last edited by javjacob on 03:00 pm May 05 2020, edited 1 time in total.
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Malibu406
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Re: 2005 kdx 220 conversion

Post by Malibu406 »

Im going to try something a little different. Im 220 lbs without gear and I think part of the issue is the stock rear spring 5 kg/mm is too soft and may be causing some of the issue up front. Racetech recommends a 5.4 for single track and 5.6 for motocross. I entered both to see the span. I picked a used 5.4 $35. Seems dumb to setup the front for my weight and not the rear. To get 95 mm of race sag I have no free sag. To have free sag I have too much race sag. Cheap way to make a step change. We shall see.

By the way Durahmtown in GA is a blast. Go if you can.
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Re: 2005 kdx 220 conversion

Post by SS109 »

Yeah, getting your suspension done is the best mod you can do to any bike. First thing every person should do is get the correct springs, front and rear, for their bike. You can't diagnose or adjust your suspension in any meaningful way without those first.
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Re: 2005 kdx 220 conversion

Post by Gixxer340 »

Malibu,

I have the same exact setup (meaning 2001 KX250 front end) and I have the same issues as you as well. I don't know what is inside the forks since I bought it that way. The bike just feels twitchy in the front end, sometime like it is on marbles. Definitely not confidence inspiring. I tried moving the forks up but it felt even more twitchy. I was thinking it might have something to do with the rear shock as well so I just got a new one to put in. Should be here this weekend so I can install it. It just seems too stiff up front and I think this plays into the twitchy-ness. I will be following this thread to see if you come across any revelations and I will post anything that I find that works as well.

Keep us posted
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Re: 2005 kdx 220 conversion

Post by KDXGarage »

Malibu, go for 100 mm. I think the 5.4 will be just right for you.

Get something up front as well, .44 or .46, depending on skill, terrain, etc.
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Re: 2005 kdx 220 conversion

Post by Malibu406 »

Its been slow going but I got the spring installed. Ive seen some be concerned with how the racetech spring guide has clearance when mated to the original spring guide, and they are correct. It is sloppy. This is because racetech and eibach springs are not tapered like the stock spring and racetech’s diametral wall thickness is too low on their guide to makeup the difference.

I corrected this by adding a third guide between the original and racetech from a 1992 kx250/kx500/older kdx p/n 13070-1161. Take a look at parts fisches, it was used for many models. It fit perfect, no slop, no pressing of guides in place.

When I took the old spring off I was surprised to see it had 40mm of preload? Still just barely had the correct race sag and of course no free sag.

I serviced the linkage and set the preload on the 5.4 kg/mm spring (5.0 is stock). Note the eibach/racetech springs are longer with only a couple of turns to start the spring nuts. Possibly my original spring took a lower set from being compressed so far.

I set preload at 11mm. Out of the gate free sag was 38mm and race sag 110mm. I will adjust to 100 mm but spring is confirmed correct for me.

Just sitting and bouncing on the bike I can tell the difference. This will definitely balance out and load the front more. Initially I set the rebound 3 clicks harder to counter the stronger spring.

I will follow up after ridding first time.
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Re: 2005 kdx 220 conversion

Post by KDXGarage »

Sweet.

Do set the race sag to 100 mm with full riding gear in a seated position before heading out.

Good idea on the rebound.
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Re: 2005 kdx 220 conversion

Post by Malibu406 »

Race sag 100mm free sag 30mm. Will recheck the front to see if it changed. I doubt it because I had the rear so preloaded to get 95-100mm with the old spring and that measurement is still the same.
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Re: 2005 kdx 220 conversion

Post by KDXGarage »

100 and 30


Image
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Re: 2005 kdx 220 conversion

Post by KDXGarage »

This is just for late night fun. :mrgreen: :partyman:
KDXGarage wrote: 05:41 pm Apr 08 2020 Malibu, go for 100 mm. I think the 5.4 will be just right for you.

Get something up front as well, .44 or .46, depending on skill, terrain, etc.
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Re: 2005 kdx 220 conversion

Post by Malibu406 »

You were spot on.

Measured front sag with gear on but not much gas. Rigged up an arrow, rubber grommets and mounts. Free sag was 40mm and race sag 62mm. So springs at .43 kg/mm are probably a touch on the light side. Possibly making a 10mm shim to try is worth considering?

On a side tangent, from my notes I see I set the 5wt oil level at 120mm. Kx250 manual and racetech call for 90mm. Not sure why I did that? That seems like the level for the old coventional forks.
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Re: 2005 kdx 220 conversion

Post by KDXGarage »

I assume your riding weight is 235. I would also assume .46, depending on terrain, skill level, alignment of planets.

Skip preloading and buy stiffer springs.

Whatever the lowest manual mentioned oil level is, go with that. You are using KX forks for trails, not a track with jumps. If you are somehow bottoming them out, then go with more oil at that point.
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