To convert or not

Questions and comments about converting to beefier forks..
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singie
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To convert or not

Post by singie »

I have been learning to ride dirt on the 2004 KDX and this is my third season on a dirt bike in the Pacific NW. I love my bike and run trails exclusively.

I am slowly getting up there in speed and feel I could benefit from having the suspension suited to my weight.

I weigh in at 195 lbs without gear and race tech tells me the rear shock at 5.0 should do me well. Meaning I just have to play with the clickers to make take off some sag and add compression to make it stiffer on my next ride and see how that goes.
The front however needs to be resprung and revalved for my weight. WHich brings me to my dilemma.

Now I did some cursory reading here and on TT and it seems like the USD fork conversion is rather popular.

I am just lost as to whether the gains to be had from going to a MX USD style fork from the stock conventional ones has real benefits? I freely admit am a noob when it comes to this sorta stuff. ANd so when i spoke to my friends about doing a KX swap, they say i am better off getting a more modern 4 stroke bike like a 2007 or newer CRF250R and having that setup for my weight instead of pouring money into my KDX.

I can find for instance KX125 forks from 2000-2003 with triple, bar clamps and axle for under 200 shipped. Can get new springs and revalved for another 400. So is it worth the extra 200$ ??
2004 KDX220R W/ Wiesco piston, Procircuit exhuast, FMF Gnarly desert pipe, Protaper bars, airbox mod
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canamfan
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Re: To convert or not

Post by canamfan »

I have a 96 kdx 200 and weigh 190, I installed race tech gold valves and .42kg springs. The forks work much better but I think I need one step stiffer springs as I bottom the 42,s out quite a bit. i have a friend that put on klx 300 forks and triples (direct bolt on) and he really likes them, I have not ridden a kdx with usd forks. However i have an orange bike with usd forks and even though it has to stiff of fork springs for me the front end is worlds better then the conventional forks. This is my first usd bike, I know i'm old school, the usd forks just feel much more accurate, if you know what i mean. When you go ride the bike with the conventional forks you'll swear it takes a second for the wheel to move when you flick the handlebars from side to side, like when your weaving thru trees. i'm considering selling my gold valve conventionals and getting usd forks for mine, theres that much difference. So yes do the conversion.
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KDXohio
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Re: To convert or not

Post by KDXohio »

I just finished the conversion on my 90 kdx200 to kx USD's and its awesome so far. I weigh 140 and the stock springs in the kx forks feel pretty good so far.

What it really comes down to is whether you want a 4stroke or not. I personally prefer a properly modded 2stroke. You already have the KDX so I'd be more inclined to do the conversion rather than buying a new bike.
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rbates9
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To convert or not

Post by rbates9 »

Modern 4 strokes will cost you far more then you could spend on keeping your KDX running. The fork swap will help if you feel the forks are holding you back. I even have a set of KX forks for sale if your interested.
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Re: To convert or not

Post by KDXGarage »

195 without gear? I would put on all the gear and check your sag numbers. I am thinking 5.2 may be needed. On the forks, I would think .44 sounds about right.

Look on eBay for a used 5.2 shock spring and buy a new set of Eibach 996 springs or Race Tech 3647 springs. Also, search for the fork shim stack mod.

Cost should be under $200.
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SS109
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To convert or not

Post by SS109 »

I did the conversion on my '90 as well. I used '96 KX125 forks and have been very happy with the results. No more flexing or catching in ruts like the stockers. I'm 150 (170 w/gear) and run .42 up front and the 5.0 in the rear. I can bottom both ends depending on terrain and how hard I'm pushing. On rare occasions (MX track, fast/rough fire roads) I wish I had stiffer springs at both ends.

Here is how I sum up the conventional vs. USD fork for the KDX IMO. The slower and/or more technical stuff I rode the stock forks worked really good for me but absolutely sucked on anything high speed (15+mph) as you could feel the forks flexing and they would catch deep ruts on occasion. Now, the USD's stopped the flex, no more caught ruts, better bottoming resistance on very fast terrain, more adjustability for the riding terrain/conditions, and revalved they are just as smooth as the stock forks and even better on the technical stuff.

Now, a 250 4T vs the KDX, that is a no brainer for me! KDX all the way! If I can hang with guys on 450F's, 250 and 300 2T's on my little KDX why go to a 250F? The KDX is rock solid reliable, the '95 and up KDX's still have all the main go fast goodies to make it even quicker, those same parts don't cost an arm and a leg like the 4T bikes (4T exhaust :shock: ), no FI or complicated electronics to worry about, actually starts when they are hot, and is way easier to work on compared to any modern 4T MX'er. If you buy a new 4T you get big cost, low resale value, and high maintenance. Buy a used one and you have no clue how it has been cared for and the resulting nastiness (grenading) that can come from it. Nope, the KDX, or any 2T for that matter, over any MX 4T for me!
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Re: To convert or not

Post by KDXGarage »

Keep in mind that 1989 - 1994 KDX200 has 4.6 stock.
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singie
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To convert or not

Post by singie »

THanks for the replies thus far. Working through the financial aspect of things to convince myself it is worth the effort now.

SO based on the reading I have done, if I was to go for a 99-2004 KX125/KX250 swap.

I will need:
Forks
Triples
Handle bar clamps
Axle
Front wheel and rotor
calipers and brake lines
THen respring and revalve for my weight for woods duty.

ALternatively if I wanted to use the KDX wheel, I will need to get the RB axle mod on my stock axle. Is there a configuration where I can use the stock caliper and brake lines?

EIther ways, I am probably looking at 400$ in addition to the repring + revalve. Being the busy season the cost for the latter is about 600$ here in Portland. Offseason costs are closer to 400 for re-spring and revalving.

Is respringing and revalving an absolute must with the KX forks or would the stiffer MX suspension actually be okay in the woods for my weight?

AM I missing anything else ?

As for the rear 0.52 with full gear, racetech suggested close to 5.0 for a rider weight without gear of 195lbs which is why I am looking to leave it as is. Although 0.52 wouldn't hurt especially as the pace picks up from ride to ride.
2004 KDX220R W/ Wiesco piston, Procircuit exhuast, FMF Gnarly desert pipe, Protaper bars, airbox mod
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Re: To convert or not

Post by KDXGarage »

Check your sag numbers on the spring. Don't shop without doing so first.

The number 1 thing you left out on a KX front end swap is the steering stem / bearing fit issue.
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singie
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Re: To convert or not

Post by singie »

Gotcha. WIll do.

ANd yes, RB designs for the steering stem issue. http://www.rb-designs.com/KDX-KX-Stem-Swap.htm

Might have to get my carb done while am at it too especially since he is local.

Thanks again!
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To convert or not

Post by rbates9 »

singie, You have your PM set to not receive messages. If you get me your e mail I can send some pick of what I have. Thanks
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