The Rad valve is a total waste of money. You get a meager, barely detectable increase in performance. For the money, you can get a good port job that will transform your bike from mild-mannered Clark Kent to Superbike.
I hadn't bought one (til last week) for the past year and 1/2 cuz I'd read the #1 part. Then my riding buddy got a reed cage from DeltaForce (not the II..it was put together just for him to try out..don't know what it is). His bike improved a good bit, so I figure it's time to change the OEM cage.
Anyway, check out http://www.boyesen.com. What they say is what I've read about how well it works. Boosts bottom end snap, increases 'overrev' to boot.
Brenda (motochick on DRN) said it was the single best bolt on she'd done (like sage sez). I bring that part up cuz there may be a point of difference that is missed when the 'yes' or 'no' part of the rad valve opinion is brought up.
I have the RB Designs carb mod..so does brenda. That may make a difference in how the rad valve works. I had read numerous 'no difference' opinions when it came to aftermarket S/As. I was surprised at the boost I got when I bolted on my PC S/A. That's what makes me wonder about the carb mod part...it may make 'things' more different than if the carb is stock.
I'll find out this coming weekend how well it works...for me, anyway. I'm already convinced it will help a hunk (just cuz brenda said!)..so I'm leveraged toward success!!!!
I guess it is a matter of perceived value. The RAD valve cost nearly as much as my port job, but I got far less of a return for that money spent. I felt that the small improvement was not worth the money.
Actually, I did the Boysen Rad Valve before the carb and it made a huge difference. It made a big change with the stock carb and still kicks butt with the RB carb. Worth every penny on my bike, which (before the carb) was ported, piped and had a free flowing SA. What kind of aftermarket valve is it? If it a Boysen it will make a lot of difference. If it is a FMF it probably won't make any difference because the FMF is a copy of the stock, only prettier.
Alrighty then, I'll break this down to give you a better view of my opinion. I started with a stock 99 220, added the pipe (FMF rev w/ powercore s/a) and tossed the airbox lid, that worked good. then pulled the cylinder to port it and raise the compression, that also worked well but still would'nt rev. then came across a 38mm PWK, WOW!, that really brought the bike to life but lost some bottom end........ bought a Boyesen Rad valve and it added almost all the bottom end that was lost by going to a 38mm carb, smoothed the powerband out and added over-rev. it was such a difference that people that had ridden my bike prior to the rad valve and then after the rad valve could'nt belive the difference, I sold four rad valve's that week! As for the rb carb mod, that also rocks! I added a divider plate after the rad valve and what I ended up with when done was a awsome engine package, more low end, big mid power & as much over rev as a 125, there's more in the engine that I can't say because I still need to make a living doing this, but if you read all the posts you might be able to pull enough info to built a clone?
I think that most if not all the bad press that these valves get is the fact that most people don't rejet to compensate for the higher intake speed, the bike goes rich, power drops and the valve gets blamed? or the bike that is getting the valve had a good design stock and a boost is not felt very much? or both?
I've used these on KDX's, KX's, RMX's, YZ's & a older CR with great results on all bikes. thats my opinion on the product and why I feel the way I do, sorry so long. :)
Here's my .02 on the rad valve subject. I have tried about all of the aftermarket hop ups avalable for the kdx, including the rad valve which I have on my bike now. I purchased it after I had FRP port my motor to help smooth out the bottom, which it did help with, but there were really no huge gains anywhere. This is compared to the two stage boysen reeds. It was easy to jet for which was nice also. The only down side that I can see is that you are stuck with only 1 choice when it comes to replacement reeds. It would be nice to be able to try some alternate types of reeds of different brands on the rad valve but they are not avalible for it. IMO there are better bang for buck hop ups, but it does help add to the whole package so it is a nice addition. I know some people who love them and some people who think that they have wasted their money, as they work better on some bikes than others depending on the needs of that particular motor.--Dan
Team-Green32 - yes to the last question, see website button for more info.
acutemp - sometimes the stock or other after market reeds will work, it works for the 00 KX125, havent tried it on the KDX though.
I have the V-Force Delta Reed cage (not the II, I guess it's the I) on my KDX. Anyways, I rejetted when I installed it, and it made a huge difference. I've installed it (the same unit, I put the stocker back on when I traded my bike) on both of my KDXs '96 & '99. I rode my '99 for a race with stock jetting and the stock reed cage. Then, I installed the V-Force and rejetted. It makes a very noticable difference. Throttle response is crisper, especially down low. Obviously, the bike revs out better and cleaner. This is done in conjunction with FMF pipe/silencer/SA, and the airbox lid removed.
If you want to know the part number for the V-Force cage, I can get it for you.
I assuming that the results with the V-Force unit and the Boysen unit would be pretty close to being the same. Anybody tried both?
The people that I've talked to that tried both said that the V-force is better. Personally I've only tried the Rad Valve (in my 99 KX250) and my opinion is that it's a waste of money. If I was going to buy another one it would be the V-Force.
Sage, it would be nice if the reeds in our rad valves would interchange with the stocker's but that would be to easy.:( The stock reeds mount with 6 screws and use a 6 window cage and the rad valves use a 4 window cage and mount with 4 screws. I have been wanting to try the carbon tech lo-tension reeds if I could find ones that would fit. Any ideas?--Dan