Hey Ninjettes!

Been a bit since I was on here since I went from the Ninja 250 to the R3, which I've been very happy with. However, I managed to snag a crashed Ninja 400 for cheap, and am aiming to race in SoCal.

That said, I still have two R3's, one street/track and one that was going to be my racebike, and may still be my B bike if funds permit.

Now onto the main topic. A fellow racer who had a pretty awesome first season as a novice racer at CVMA this year, placing a good number of 1st and 2nd places, crashed last round due to multi-racer pile up, and I managed to get some parts off the crashed bike since he opted to buy another one before this weekend's final round as he had a shot at winning the championship.

One of the things I realized looking at Racetech's suspension calculator and parts nubmers, is that the spring rate for the Ninja 400 is .77kg/mm, as opposed to the R3's .65kg/mm, and Racetech recommended .78kg/mm for my R3. Since they're both 41mm forks, with similar fully extended lengths, and the racetech spring part numbers are the same for both bikes, I snagged the Ninja 400 springs for my R3. All I had to do was cut new tube spacers (which I just cut from the Ninja 400 tubes I got with them).

However, my friend said he'd never touched the forks on the 400 he crashed, but the springs were progressive, which is cool but I can't find anywhere wether that's how it actually comes from Kawasaki or if they're aftermarket springs. The parts diagram doesn't show progressive springs, and every time I try and locate any info, it's all aftermarket talk and info.

Does anyone here know if they come from the factory like that? Sure, I could just pull my 400's springs, which I will when I install my pre-load adjusters, but those will take a moment to arrive, and I miss this group so I figured I'd make a post.

Good question - will bump it to the tech area for more views and hopefully some useful responses. :thumbup:

Thanks man!

Yes, the stock fork springs are progressive. I thought I took some pics when I swapped in my RaceTech springs, but I can't seem to find any.

As a follow up now sometime later, here's what I've learned.

1. Yes, they're progressive but a much improved spring rate that works better for street/track use over previous generations. I'm riding A group at Buttonwillow on stock fork springs, but with 20wt oil and pre-load adjusters. (I weigh 145lbs currently)

2. For those with an R3 (don't witch hunt me Ninjette's lol, I own both currently) swapping in the springs and spacers from the N400 to the R3 vastly improves it's handling. Highly recommend on a budget.

3. Despite my friends winning amateur class championship and me riding A group on stock springs, I'm still opting to get a full set of cartridge inserts for full damping control, that will also be sprung to my weight and riding ability.

In short, TLDR, for 90% of Ninja / Z 400 Riders out there, even for the track, the stock springs will take you into racing just fine, but are still worth upgrading.