I've seen plenty of threads on installing different rear shocks, but what about the front? What kind of changes are available for our pregens? Can we use the new gen ones or do we steal them from other bikes? Anybody done anything with the fork springs?

http://faq.ninja250.org/wiki/Front_suspension_upgrades

Straight rate springs are pretty much what everyone recommend these days like Race Tech/Sonic Spring and they run about $90 a set. They have application available for all models and years of ninja 250's

Progressive Suspension springs are all the rage back 15-20 years ago...80's and personally I still swear by them. Progressive springs have kind of fallen out of favor so you can find them less then $70 or $60 at time so its vary good bang for the buck in my opinion. I have installed them on all of my bikes and many friends have also try with good results.

But on the 250 I think Progressive did not spend enough R&D time on the 250 spring rate as its vary plush in the initial travel and firm up vary rapidly perhaps too fast but its still a vast improvement over stock. Ninja250.org did not recommend Progressive Springs but my opinion is that just becasue they did not pick a good spring rate for the 250 dosn't mean you should not try them for all bikes.

I would not touch a spring that is progressive for any race application. The act of a rapidly increasing spring rate can get you in trouble fast on the track, especially on a bike. People who run a standard spring rate will almost always out run anyone on a progressive setup. I could deal with my soft suspension a lot more than going progressive. That sudden firmness can cause a load on the front tire in a corner, bye bye front end. Granted, that is in extreme racing conditions, around town and for spirited backroad riding, that may work just fine.

I'm just not a fan of progressive rate springs, can you tell? :D lol

I think both camps on spring rates, either linear or progressive have their points and valid from their perspective.

The idea of using all of your travel sounds great on paper but does anyone realized that your bike geometry especially the head angle change drastically when you fork compress to full travel? Every inch of fork travel will alter your head angle by 1 degree, my 250 got 5.5" of travel so thats a 5 degree of possible change in geometry if I used up my fork travel and that is huge change.

Suspension engineer alter head angle by 1/4, 1/2 and 1 degree at most so if your at a track mid corner and hit a pot hole LOL and your fork dive beyond 3.5" of travel, I doubt you'll be able to steer your bike out of the pot hole/corner without severe stability/headshake problems and possibly crash becasue of it. If you can properly maintain your bikes geometry that translate into stability which = confidence= faster speed.

Where I think straight rate spring will benefit the most is on off road dirt bikes that need every inch of travel their fork can dish out to maintain control of their bike in rough terrain. On smooth pave road or track, I doubt you want or need your fork to move more than 2.25" of travel to deal with surface irregularity of asphalt.

Progressive Springs were develope back then when valve emulator does not exist yet so they got a lot more issue to content with. Would I buy straight rate springs? you bet if they cost $60 istead of $90 :D

I would just replace the fork oil to 15wt and put 1.5 spacers with stock spring and skip the whole debate on which springs to use

hey guys i have a ? im installing sonic springs on my 250 and i was just wondering how you line up the forks so the wheel wont be crooked after you set the height for the fork and triple tree??

replace them with ... other springs!

Look at the fork tubes from one side or the other, right at the leading edge, you will be able to see if they're not parallel.

My method is to loosely mount the forks first, align the wheel, and then set the fork height at the end. To align the wheel place an object under the tire to take the weight off the forks. Undo all the fork mount bolts at the same time, shake the bars a little, then redo the bolts. Take away the object under the tire and make sure the wheel spins freely. Then set both fork heights evenly and lock down both forks. Check that the wheel spins freely and then lastly, attach the brake and pump the lever. Of course you can take a small shortcut if you find an object (or shim one that is almost tall enough) that will support the wheel and forks at just the right height.