Rebuild stock forks or upgrade on 1991 KDX 250?

lcc

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#1
I have a 1991 KDX 250 that is almost perfect in the woods, but the front suspension feels 'soft' when trying to rail through a turn in the woods or on light motocross tracks. I can't 'feel' the front and when trying to speed through a turn I sometimes wash the front because I can not 'feel' the front through the turn. I've ridden other newer bikes lately and they don't have this feeling and I can turn much faster and more confidently. Should I have someone re-valve my forks (they are basically unadjustable) or would it be more cost-effective to buy some used KX forks or what? Any ideas or solutions would be helpful. I apologize for my lack of skill in describing my front end woes, but trust me that it isn't all in my mind...all my buddies feel it when they ride it too. Thanks...
 

dirt bike dave

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#2
Whether you revalve and respring or replace your forks, your bike will be dramatically improved.

The stock KDX250 forks have way too soft a spring and way too much high speed compression damping. The result is the worst of all worlds - can't handle whoops and jumps, but too harsh on rocks and roots.

Besides stiffer springs, I put Race Tech gold valves in mine and used less high speed compression damping than the RT charts called for. I also raised the fork in the clamps and ran no pre-load on the springs, so the front would dive down more on cornering (the stock frame is slow steering). It was a huge improvement in the overall handling and capabilities of the bike, and it really helps your confidence in the bike. The stock forks are truly grim.

Other little things you can do to your KDX250 are to shave the seat foam down at the front. This will allow you to get into a better position when cornering, even if you are tall. If you run a 13t countershaft, you can shorten the chain and pull the rear wheel all the way forward on the swingarm to shorten the wheel base. A steering damper is also a good investment, and you can transfer it to your next bike.
 

lcc

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#3
DirtBikeDave and any others, who would you recommend I contact about rebuilding (not just spring swapping) the stock forks?

I'm glad you recognize what I'm talking about here...I think it is totally spring rate but with no adjustment a rebuild has to be just right. Thanks for the reply.
 

dirt bike dave

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#4
Once I got mine set-up I preferred my 250 to my KDX200s, but the forks and jetting were way off stock (the 200's have similar problems, just not quite as bad). The 250 is a good bike underneath, though. Kind of heavy, but reliable and powerful enough, with a nice big tank.

If there is a reputable suspension shop in your area, you might call them and talk to them about it. You don't identify your location, but let us know where you are and someone may have a recommendation.

I have had good luck in the past with Factory Connection, but I don't know if they work on your old forks.

One thing you should think about is whether a revalve/rebuild or a fork swap is worth it on a 15+ year old bike. You could easily spend $300+ upgrading the old war horse, and you may be better off selling it as is and putting that money toward a new bike.

Good luck with whatever you decide. BTW, if you search this forum you will find some additional info on fork swaps. Virtually anything you can find would be better, but to maximize the improvement you still might need to revalve for your conditions.
 
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#5
Yeah man I feel the same thing when railing turns and I only weigh 130 pounds. Oh well...I don't have the money for some KX forks so I'll just have to live with it.
 

dirt bike dave

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#6
Nick90 said:
Yeah man I feel the same thing when railing turns and I only weigh 130 pounds. Oh well...I don't have the money for some KX forks so I'll just have to live with it.
If your bike is an '89 KDX200, I highly recommend Race Tech's cartridge fork emulators. You can install yourself if you have some mechanical ability. You can also stiffen your wimpy stock springs slightly by cutting off a few coils. Free and it works. Make sure you don't cut off too much or the coils will bind and prevent you from getting full travel.

Not sure if RT still makes the emulators, but they really work.
 
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#7
You might want to try just the fork springs before worrying about the damping. Once you get the correct rate fork springs (and shock spring if needed), you can better evaluate the damping.

On the forks, there are compression adjusters on the bottom of the fork tubes. When new, there were rubber plugs covering them. If you still have them, check that. There are adjustable screws on the bottom. Just DON'T turn them in all the way and crank on them. Just lightly turn them in.
 

dirt bike dave

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#8
glad2ride said:
You might want to try just the fork springs before worrying about the damping. Once you get the correct rate fork springs (and shock spring if needed), you can better evaluate the damping.
No matter what you do with the clicker, the '91 -'94 KDX250 fork has way too much high speed compression damping. Even with the stock extremely soft springs the fork is harsh on rocks and roots. While stiffer springs alone will improve the fork on big hits, they will make the rocks/roots problem even worse.
 
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#9
If it is still way too harsh with the oil bypass all the way open, then it makes me wonder about the bushings and seals, oil weight, etc.