I finally found a shop that has a set of springs for my 93 KDX 250 but they are progressive springs. Does anyone have any experience with these? I would assume that any aftermarket spring is better than stock. The owner tells me they are 34-41 pound progressive rate springs. I'm not sure how that relates to kg/mm rating of other springs. I know my stock springs are straight-rate, how will the progressive rate act differently? Any advice would be appreciated.
Progressive Suspension Fork Springs
- Thread starter exbee
- Start date
12" travel with 43mm tubes won't need progressive as the air pressure in the fork goes up with travel.
2.204 lbs per kg 25.4mm per inch. They're way too heavy.
I think (edit, klx250 for my sr model) springs come close, you won't need the original free length, much shorter for a decent rate spring.
Too tight to buy springs so I teed mine into a schrader valve and run air pressure.
http://i698.photobucket.com/albums/vv347/Tom65/BMX6.jpg
2.204 lbs per kg 25.4mm per inch. They're way too heavy.
I think (edit, klx250 for my sr model) springs come close, you won't need the original free length, much shorter for a decent rate spring.
Too tight to buy springs so I teed mine into a schrader valve and run air pressure.
http://i698.photobucket.com/albums/vv347/Tom65/BMX6.jpg
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I suggest you do not do it. Almost all suspension tuners go with straight rate springs for off-raod bikes.
Is 170 pounds your weight with all riding gear, toolbagm water backpack, toolbag on bike, etc.?
What is your skill level, riding terrain, racing or putting along with the kids, etc.?
A .42 or .44 Kg/mm rate spring is probably going to be what will work best for you.
This will sound odd, but it is the best way I have found to go on the 1991 - 1994 KDX250 fork springs. Buy some RT 3949 or Eibach fork springs. They are the ones for the 1993 - 1995 KX125 and KX250. You will probably need to file, grind, sand or lathe down the outer diameter of the white, plastic fork spring guides that fit inside the springs. Stiffer springs have larger diameter coils. The fork tube diameter prevents the spring from being made larger in outer diameter. The outer diameter must remain the same. Therefore, the coils are larger to the inside of the spring. You will also need a spacer to make up the distance from the top of the spring to the underside of the fork cap. The reason for this is that the new fork spring is not long enough. For example, the Race Tech 3949 springs are 487mm long. A 13mm long spacer (1 1/4" PVC pipe) will make the spring and spacer combo length equal 500mm. This will give 10mm of fork spring preload, which is what Race Tech recommends. When Eibach was still making their 997 model of fork springs, it was 500mm in length. It was marketed for the 1991 - 1994 KDX250.
Is 170 pounds your weight with all riding gear, toolbagm water backpack, toolbag on bike, etc.?
What is your skill level, riding terrain, racing or putting along with the kids, etc.?
A .42 or .44 Kg/mm rate spring is probably going to be what will work best for you.
This will sound odd, but it is the best way I have found to go on the 1991 - 1994 KDX250 fork springs. Buy some RT 3949 or Eibach fork springs. They are the ones for the 1993 - 1995 KX125 and KX250. You will probably need to file, grind, sand or lathe down the outer diameter of the white, plastic fork spring guides that fit inside the springs. Stiffer springs have larger diameter coils. The fork tube diameter prevents the spring from being made larger in outer diameter. The outer diameter must remain the same. Therefore, the coils are larger to the inside of the spring. You will also need a spacer to make up the distance from the top of the spring to the underside of the fork cap. The reason for this is that the new fork spring is not long enough. For example, the Race Tech 3949 springs are 487mm long. A 13mm long spacer (1 1/4" PVC pipe) will make the spring and spacer combo length equal 500mm. This will give 10mm of fork spring preload, which is what Race Tech recommends. When Eibach was still making their 997 model of fork springs, it was 500mm in length. It was marketed for the 1991 - 1994 KDX250.
- Thread starter
- #6
I'm 170 with no gear. I'm a new offroad rider but not new to motorcyles. I've been riding on the street for years and roadracing for the last 3 years. I plan on mainly trail riding but also want to try a hare scramble or two.
My local suspension shop is looking into springs for me and suggested they could get Eibach to make custom springs for a little extra money. I already mentioned using a shorter spring with a spacer and they told me it was not a good idea...I forget exactly why. I know the complete KX conversion is the best route but for this year I'd like to just switch springs.
My local suspension shop is looking into springs for me and suggested they could get Eibach to make custom springs for a little extra money. I already mentioned using a shorter spring with a spacer and they told me it was not a good idea...I forget exactly why. I know the complete KX conversion is the best route but for this year I'd like to just switch springs.
Pete Payne
MX-Tech Suspension Agent
- Nov 3, 2000
- 933
- 38
exbee said:
34 lbs/inch is .60/mm
41 lbs/inch is .73 kg/mm
sounds WAY stiff to me .
Give cannon racecraft a call.
the stock rear spring was a 4.9kg/mm and should be good for you .
Up front the stock was a .34kg/mm and you need a .43kg/mm
exbee said:
I think a Race Tech 3949 in .44 Kg/mm rate would be OK for you. If you want to try .01 Kg/mm lighter or stiffer, go with an Eibach 989 model series spring. They are available in .37 Kg/mm - .47 Kg/mm rates, by .02's (.37, .39, .41, .43, .45 and .47 Kg/mm). Race Tech makes the 3949 in rates from .36 - .46 Kg/mm rates by .02's (.36, .38, .40, .42, .44 and .46 KG/mm). Race Tech springs are 487mm (13mm spacer needed). Eibach springs are 486mm (14mm spacer needed). Both brans of springs come with packs of washers so you can set the preload you want. The spacers (PVC pipe sections, or go all out with some 6160 aluminum solid rods drilled out to spec) would go on top of the springs.
It is my understanding that forks in the last 20 years are pretty much all USD and come with a certain length spring that doesn't require any spacers (unless amount of preload is to be changed for additional preload).
If you go with the custom Eibach springs, could you please take a picture of the installer's face when he gets the spring stuck on the stock size inner spring guide? :yikes: :rotfl:
Ask them how many sets of aftermarket springs they have installed in 1991 - 1994 KDX250 forks. ;) Heck. Just ask them how many sets of 1991 - 1994 KDX250 forks they have worked on period. ;)
Good luck with it, no matter how you go. :cool:
glad2ride said:
Still too cheap and my sr fork appears to have a different internal length. 455mm no preload hence my concern for coilbind in mine at least.
Happy enough with air for now, have to strip them again one day to try valve mods but been doing a lot of riding and getting complimented on the KDX's performance by guys that have spent up big on current bikes.
Unfortunately, far too many riders think this way.exbee said:
We seem to feel the factory engineers are more clueless than any jamoke who manufactures an aftermarket part for their bike, or makes a part that will even remotely fit their bike, or any part they take off a completely different bike that can be hammered onto their bike.....
I've found that if you are going to replace a stock part on a bike, you'd best have a very good, and proven, reason to do it. Otherwise you'll end up with a bunch of mismatched, expensive pieces that work worse than the stock parts.
- Thread starter
- #17
glad2ride: you understood what I meant. I know how soft the springs are therefore I thought anything heavier would be better no matter who makes it. I wasn't a sweeping statement about aftermarket parts. There is definitely a lot of junk out there to be bolted to a bike!
mudpack said:
Um, Have any explanation for the front of the KDX being sprung for about a 90lb rider while the rear was good for 160lb rider? The front springs in the KDX are crap, regardless of how infallible you think the kawi engineers are. The bike is unbalanced from the factory, any way you look at it.
That said, you do make a valid point. Different does not always = better!
I think after the last model kdx was developed in 1995 the project was orphaned by the engineers and the art department was forced to come up with various color schemes and graphics over the next decade, that is untill the engineers where forced to do something so they came up with the cylinder design for the 220 but in spite they designed the piston to be a time bomb.. maybe the engineers never read reviews throughout the 90's....
but the same can be said for yamaha and their xt350 they changed nothing for nearly 20 years on that bike except the colors and the xt350 had really soft suspension worse than the kdx
I think if its not a race bike the big 4 won't listen to feedback the big 4's on/off bikes (enduro) have always been heavy pathetic pigs,same can be said for thier "dirt" bikes though my xt350 is very light compared to the rest I believe its 260#
but the same can be said for yamaha and their xt350 they changed nothing for nearly 20 years on that bike except the colors and the xt350 had really soft suspension worse than the kdx
I think if its not a race bike the big 4 won't listen to feedback the big 4's on/off bikes (enduro) have always been heavy pathetic pigs,same can be said for thier "dirt" bikes though my xt350 is very light compared to the rest I believe its 260#
- Thread starter
- #22
Well, I just ordered the RT3949 springs. Their calculator said I needed a 0.422kg/mm spring rate but they don't make the 0.42 anymore so I ordered a 0.44 set. Hopefully a little too stiff is better than WAY too soft....
Someone mentioned that I should get 0.44s anyway...maybe the RT calculator leans to the soft side??
Someone mentioned that I should get 0.44s anyway...maybe the RT calculator leans to the soft side??
helio lucas
~SPONSOR~
- Jun 20, 2007
- 1,020
- 0
julien_d,julien_d said:
most dual sports are made to carry a passenger. if the shock was sprung lightly as soon as you put there two persons the shock would bottom out. have you do\seen someone carry a passenger on a MX bike?
sorry but i don´t agree that the kawasaki engineers don´t know what they do. they have to make choises, they are compromised and i believe the maketing departement is who build current bikes :(
the engineers are great, they make the KDX work great in anything with minor adjustements... all of that at an acessible price...
