Posts
196
Joined
3/9/2022
Location
Ontario, CA
Anyone have experience with the JBI XACT48 DIY kit compared to a spring conversion on the 23-25 KTMs? In my case a 350.
Trying to decide if its worth the cost to give it a try. I am in Canada. So buy the time I pay exchange rate, shipping, taxes and duty its not as cost effective as the published price. Still considerably cheaper than a spring conversion though.
The reviews I have read seem positive, but not sure if those opinions are a bit blown up.
Hoping some guys have some experience with this kit as well as the 6500s for comparison.
I put the DIY kits in my fork and shock (23 350). I don’t have experience with the spring conversion but my last bike had KYB forks. I’m pleased with the performance and glad I didn’t spend the extra for inserts. The recommended settings were spot on.
What are you looking to get out of the bike that it’s not giving now? This will probably determine the answer. I’ve ridden both, back to back.
I have the fork kits. I cannot compare to spring cartridges, or other brands, as its been so long since I’ve tried them. The track I've been riding is very rough so I’m not sure any fork will feel smooth. Though, I don’t have any major complaints with the forks now. If I try 6500s it will be to see if braking in large bumps is any smoother or of the front will feel better in flat corners.
Thanks guys!
Owen - Good question!
I am looking for a more comfortable feel track to track. More plushness in the beginning of the stroke. Better holdup on braking bumps coming into corners while maintaining comfort, but Increased bottoming resistance without sacrificing so much small bump and chatter comfort.
What I am finding with the stock air forks is that in order for "me" to get them feeling comfortable in the chatter and small bumps, they tend to blow through the stroke easily, giving up bottoming resistance on jumps. If I adjust them to prevent regular bottoming they lose their small bump comfort. I cannot seem to find a middle ground. Regardless of air pressure and clicker settings. It feels like a trade-off. Either harsh on small stuff with satisfactory big bump hold-up and jump bottoming resistance, or comfortable on the smaller braking and acceleration chop but giving up bottoming resistance.
For reference, I also own a '24 KX450 and most past experience is with spring forks. I am "sort of" using it as a reference point. Of course I realize a WP air fork is never going to feel like a Showa spring fork. I have been trying to give these WP's a fair chance based on the number of comments I read about how much improved they are over previous generations and near on-par with spring fork bikes in many areas. I am just having a hard time finding a happy medium.
It should be stated that I am 6'4 and 230 before gear. So I am sure my height and weight play a role in my experience!
Hence the question around whether it would be worth giving the DIY kit a try before investing in a spring conversion. Or save my money and go straight to a 6500 or KYB conversion.
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Free shipping: VITALMX
There's a member here who makes a cheaper spring adapter allowing you to use KYB internals. Give it a search
This isn’t going to make your decision any easier, but the new valving increases the damping and allows much lower air pressures doing what you are asking for.
“What I am finding with the stock air forks is that in order for "me" to get them feeling comfortable in the chatter and small bumps, they tend to blow through the stroke easily, giving up bottoming resistance on jumps.”
Within the range of his recommended settings I find I am at the lower end of the air pressure and compression settings. In fact I think i’ll go even lower on air and add a bit of compression damping back. That is for a very soft, rough track. I weigh 185-188 and am in the mid to low 140s for pressure. I finally got it to bottom on a decent size jump with a flat landing at 144psi/22 out in compression.
Have you tried increasing oil volume? I ask because, the condition you describe, difficult finding that middle ground, becomes more and more of an issue the bigger the rider is because you have to run such high air pressure. The more air pressure you run, the more you pronounce the negative effects of an air spring (loss of small bump sensitivity). And this will be even more true if you do not increase the oil volume to obtain some more progressive action and bottoming resistance. Put another way, increasing oil volume may allow you to lower the psi and/or open up the compression to get back some plushness in the initial part of the stroke.
Agree, the oil volume makes a huge difference in these I just experimented a bit with mine even as little as 10cc brought up my bottoming height on the same test loop up about a 1/4".
Thanks for the feedback guys. I have thought of it in passing in the past but not thought much of it for the air forks. I did add some on the KX and made a notable improvement. Ironically have not thought seriously about it, but it makes sense! Definitely add that to my 'to-try' list. Very cheap option to try after all.
Not to stay off topic though. Maybe oil alone will be the answer. But assuming I am still looking for more. Still interested in collecting additional opinions on the JBI air kit vs. a spring conversion. I should note, I am a mid 4-'s vet rider, mid to front of C class rider. So not pushing the bike hard from speed, but from height leverage and body weight.
To answer that exact question, it all depends on the setup. I have 1 bike with JBI DIY kit and another with JBI 6500's. I could see where either of them would be preferred, depending on the rider's preferences. Important thing is to be very accurate with the info you give JB so that you get the best result with whichever you go with.
I am your exact height and weight. I came to the conclusion that I am too big to get the WP air forks to work right for me. In order to have the holdup and bottoming resistance I need for my weight, I had to inflate the fork to 165+ psi. Obviously this lead to an extremely rough front end, and I also frequently washed out the front end. The RT setup fixed everything for me and I'm sure the JBI kit is really good too, I haven't heard anyone say anything negative about it.
Have you ridden a soft, rough track with both? If so, which do you prefer? Harder packed, less rough?
Another way to look at it, what do you feel the 6500s do better?
I’m not really unhappy with my JBI DIY XACT forks, but considering 6500s just because… well, maybe they are better?
I prefer the 6500's, but I think most of it is the setup is better. My forks with the DIY are a little too soft. They are great if the track has no giant hits or G-outs, really good on the chop, but don't quite have the hold up and bottoming resistance of the 6500's. Again, I think mostly due to setup. I could likely get the DIY's pretty close to the 6500's, but I currently have them on a 125 so not too worried about it.
On hard hits with the aer, do you ever feel like your hands are about to blow off the bars, just to realize you didn’t even bottom the forks out? I always assumed this was because of the bottoming cup on the 23-24 forks
No, not really. But I have to admit I am not super picky about suspension setup. I'm one of those get it close and just ride it kind of guys. I am pretty sensitive and knowledgeable to what it is doing, I just don't get really bothered by it unless it's pretty far off. I've been running my 3rd bike, 2025 FC350, pretty much totally stock for almost a year now. Sag and a few clickers here and there and I'm happy with it.
The JBI valving seemed to help that. Seems to rely more on damping which responds more on hard hits than spring rate.
We've had the stock AERs, the JBI DIY kit, a set of WP6500s JB did, and MX Tech Luckys on our Austrian bikes since 2018. TBH, there's nothing like a spring fork. First thing we did with our new 24.5 GG 250 FE was move the 6500s over and put the 24.5 AER internals in the other bike. My rider was instantly faster and more confident on the spring kit. You really need to ride both - if you are fast it's all subjective. There are plenty of fast riders that like a properly setup AER. My son can go fast on any of our forks but he prefers the 6500s over the others. For an old slow fart like me it doesn't matter as much although I still prefer the feel of a spring fork every time.
FWIW if it's me I'm installing the 6500s. Easy DIY job and best bang for the $$$.
Post a reply to: JBI XACT48 DIY Kit 2023+ KTM