KDXRIDER.NET

Searched. Found nothing. Probing to see if anyone has tried the new plastic from Moto Tass. Have nothing against running a 3, might as well as if the 4 is worth the coin.

There's a whole long story behind the question, the short is that intake boot is fragged, didn't want to spend $80 for a new one, reeds were chipped, bought boyesen for the intake boot, did research, found they actually kill the KDX in its tracks in a certain sense, now looking to possibly machine rad valve down to factory intake shape and put v-force after of it, then port/port match the rad valve intake manifold. Again, more to it than meets the eye, this is a very far zoomed out synopsis of my current thought process . Lot of work and money for a stupid reed valve system. Again, there is more to the story that is irrelevant to if someone has tried the vforce 4.

Money and cost is a non-issue if you couldn't figure that out on your own.

Happy memorial day. Thank you to those that kept the world safe during the 20th century and all those before and after!

I didn't even know they had started offering a "4" version for the KDX. They didn't when the "4" first came out. Cool to see that they do make one.

https://mototassinari.com/finder-results/v4r13g.html

Then test subject I shall be..

Let us know how it turns out. Thanks for spurring me to research it further.

Problem is that riding season just ended here so will be 4+ months before I really get to experiment with this, but I will try to post my experience when it happens!

Is it already that hot or law related??

KDXGarage wrote: 05:23 pm May 28 2024 Is it already that hot or law related??

Yessir. Texas is under the torch right now. Which is odd because as I type this we are getting nickel size hail coming down like a downpour. But it's already 100 almost everyday, so I might hit the MX tracks, if they decide to open before noon, a few times this summer, but generally, the season is over here. I won't take the KDX though, probably the CR125

Wow. That is rough. I think we are mid 80's of late here in north Alabama.

smelonas wrote: 07:48 pm May 28 2024 Yessir. Texas is under the torch right now.

You just gotta get up earlier! That's what we do here in Arizona. I like to be on the trail by 6am at the latest during the summer. I get out, hit it (25-40 miles), load up quickly, and home to the A/C!

SS109 wrote: 10:02 pm May 28 2024

smelonas wrote: 07:48 pm May 28 2024 Yessir. Texas is under the torch right now.

You just gotta get up earlier! That's what we do here in Arizona. I like to be on the trail by 6am at the latest during the summer. I get out, hit it (25-40 miles), load up quickly, and home to the A/C!

I'm from Vegas. I know how it doesn't cool down at night, and riding really is not fun during summer. It actually cools down here at night, usually 70s, sometimes 60s. But the drive is long and the snakes are prolific out here. Bag of excuses, I know, but summer is when I get my maintenence/tear downs and house stuff done. I stay plenty busy, don't worry. Always have an excuse to work and not ride!!

Have you actually tried a RAD valve? They do quite well. I would much rather have aluminum than a block of plastic as my reed cage.

Chuck78 wrote: 09:12 am Jun 02 2024 Have you actually tried a RAD valve? They do quite well. I would much rather have aluminum than a block of plastic as my reed cage.

It's a quality piece, but it's quite obvious that the intake manifold is a choke point compared to the OEM tract. Would need quite a bit of porting to open the throat up to match OEM.

I havent ridden it yet, but I've developed an occasional bog in the mid range that I gave up trying to fix for the time being. I have one on my CR125 and that thing rips.

Plus I like trying new stuff and I have broken stuff I need to replace, so why not mess around. You won't find out trying what everyone else has already tried.

smelonas wrote: 08:19 am Jun 11 2024

Chuck78 wrote: 09:12 am Jun 02 2024 Have you actually tried a RAD valve? They do quite well. I would much rather have aluminum than a block of plastic as my reed cage.

It's a quality piece, but it's quite obvious that the intake manifold is a choke point compared to the OEM tract. Would need quite a bit of porting to open the throat up to match OEM.

I havent ridden it yet, but I've developed an occasional bog in the mid range that I gave up trying to fix for the time being. I have one on my CR125 and that thing rips.

Plus I like trying new stuff and I have broken stuff I need to replace, so why not mess around. You won't find out trying what everyone else has already tried.

Did you ever try out the VForce4? Or the RAD Valve? I have a RAD Valve and a VForce3 and an OEM intake and reed block with Boyesens. The RAD Valve was specifically designed and ported for the KDX to optimize air velocity, it's not that it restricts the airflow, it just directs the airflow velocity in a way that it opens the read petals more. They definitely behave slightly differently than the VForce3, but that's not necessarily a bad thing. Due to the differences in my three engines, I couldn't tell you exactly an apples to apples comparison without trying them all on the same engine back to back, but I do definitely like the RAD Valve, & am picking up another one, but also likely to try a VForce4 at some point.

I have RAD valve on my CR125 and it works great. It has quite the quality feel to it, especially because it is made of aluminum and not plastic like the VF3 on my KDX.
Performance wise I have no clue as they're on two different bikes, but I may pick up a RAD valve for my KDX. It is a really well built product. And the fact that the intake manifold is all aluminum and the boot on it is easy to find makes it worth it. The reason I have one on my 125 is because the OEM manifold was dryrotted and causing an air leak, and a new intake manifold was just as much as the RAD valve.
...And honestly, I'm not skilled enough on the bike to take advantage of any extra power it may provide (at least up top) hahaha, so the difference to me is moot unless one of them makes noticeably more low end torque than the other. But I don't know the nitty gritty of which may make more power and HOW it makes that power.

Chuck, you say the RAD valve behaves differently than the VF3, in what way does it do so that makes you like it?
Thanks

SpruceItUp wrote: 04:21 pm Mar 17 2026 I have RAD valve on my CR125 and it works great. It has quite the quality feel to it, especially because it is made of aluminum and not plastic like the VF3 on my KDX.
Performance wise I have no clue as they're on two different bikes, but I may pick up a RAD valve for my KDX. It is a really well built product. And the fact that the intake manifold is all aluminum and the boot on it is easy to find makes it worth it.


Chuck, you say the RAD valve behaves differently than the VF3, in what way does it do so that makes you like it?
Thanks

The RAD Valve is obviously the better design/build quality, with a generically replaceable coupling to connect the carburetor, instead of the OEM molded intake manifold boot.
The VForce has a quicker throttle response on the low end, but the RAD Valve has power gains everywhere else that the VForce3 does, and seems to smooth out the hit when the power valve opens a bit better, although this could be due to differences in atomization through the higher velocity through it.


Apparently the rad valve with the upgraded carbon fiber reeds improves the response on the low end exactly the same as the V-Force3, according to another forum member SS109 .

The RAD Valve's reed placement angle is a bit greater, causing the reeds to have to bend further, although durability of the reeds seems to be a non-issue. The VForce3 places the reeds at a more relaxed angle so that they do not have to open as far, and they have a larger reed area.
There have been a few complaints of people saying that the plastic VForce reed cages are able to be easily distorted and sometimes show up new from the factory with a slight distortion so that the reeds do not seem to seat fully closed on them.

I'm very likely picking up another RAD Valve from a member here, but also later this year, would like to pick up a new Moto Tassinari VForce4 reed cage to compare and try out.

In the past, it seems the VForce3 performance has been preferred in the KDX community, but with the carbon fiber reed petal upgrade, perhaps this was a non-issue?


EDIT - apparently Ron Black was saying that the VForce or stock reed setup using the stock type full intake manifold boot is better for the carburetors, as it dampens engine vibrations more due to having a greater length of rubber between the engine and the carb, and the needle jet and jet needle in particular will experience more wear with use due to the engine vibrations. Another forum member seemed to interpret this as the RAD Valve's coupling style will wear out the slide faster, but with the slide being covered in premix and being a snug fit in the bore vs an open orifice and a full circle tapered needle loosely blocking the orifice at varying throttle positions, this obviously is going to be the primary focus of the wear concerns. I feel this is not going to be as much of an issue on Lectron carbs, Lectron Billetron Pro Series carbs, and the new SmartCarb SC3 34mm metering rod carbs, as they aren't a fully tapered needle - their metering rods only are tapered with a flat bevel on the backsides, and therefore will remain in roughly 50%+/- contact with the receiver portion of the carb body instead of loosely plugging the metering orifice.[/I}

I actually hadn't read up on the changes to the VForce4 over the previous VForce3 generation until now:

KDX200/220 & older KX125 model page, Moto Tassinari part # V4R13G :
https://mototassinari.com/v4r13g.html
(this fitment is not listed in the generic VForce4 page, no Kawasaki even listed yet despite being out for over a year now...?)

Here's from the main VForce4 page, a bit different description vs the KDX-specific fitment:


"The VForce4 is built upon the solid foundation that made the VForce3 reed valve system such a success for over fifteen years. While the VForce3 has been continually refined over the years (including the latest VForce3R models), this is a complete redesign of the entire system. We jokingly say, "The only thing we didn't change is the bolt pattern." However this is actually quite true. All the components that go into making a VForce reed valve system have been significantly changed since the VForce3.

The reed cage design now incorporates an airfoil shape at the reed tip area to increase air velocity from the outer ports. We use an all-new reed petal resin system, carbon fiber and lay-up on our new pre-curved reed petals. The benefit of the pre-curved reed petal is better sealing at the tip area. The VForce4 also features longer reed stops to progressively slow petal tip velocity, for increased petal durability. The combined reed tip area has been increased by over 10% resulting in increased total airflow. Finally, we reduced frontal area of central wing by 15.6% combined with a more aerodynamic shape.

The all-new VForce4R models incorporate a rubber overmodling on the reed surface to drastically increase reed petal life, while also creating a superior sealing surface."




***A MAJOR WORD OF CAUTION - eBay is flooded with these "V4R13G" models for $60-$100-ish, vs a fair amount of them priced $170-$255... This screams fakes, buyer beware... I feel sad for all those who think they're saving money and getting a great deal on these when they are buying forgeries that are not likely the same quality and performance as the genuine versions.... They're $175 on the manufacturer's site, I would strongly advise buying them direct.