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
Dan if you can find a set of Carbon Tech low tension reeds for a 1989 to 1993 KX125 I think your chances would be good that they would fit in your factory reed valve. Have you tried Boyesen Pro Series reeds with the carbon fiber top reed?
Dan, take a look at stock 00 KX 125 reeds, I think they might work.
as far as the v-force vs. rad valve thing I've tried them both it 200 and 220, the v-force reed tend to make big mid & top, where the rad valve makes good bottom & mid with a good top also, not as much top end as the v force but its not far off. the biggest thing i've seen with the v force reeds is that with stock compression they lack the low end.
Dave, my bike is almost back togather and I'm interseted in the dyno stuff you were talking about, I have lots to test and the testing will make good writing for the site. this is what I have for testing, any more ideas from the croud would be great.
stock vs. my bike
my bike vs. a Fredette bike (if its still availible?)
KDX vs. EXC (both are built)
rad vs. v force vs. stock reed cages (we will put this to rest finally)
38mm carb vs. 36mm vs. stock
Anymore ideas would be good, please email me. (keep them real please!, I'm not going to put a nos kit on the kdx........... yet!) :cool:
You're right you are missing something. Boyesen originally installed Power Reeds ( fglas to fglas ) in RAD valves. Those, like myself, who picked up their RAD valves earily on have the option of using either reed, well until the orginal reeds wear out anyway ;).
Dan runs a 95 KDX so if he picked up his valve when the bike was still newish chances are fairly good his RAD valve came equiped to Power rather than ProSeries reeds.
Yep, my rad valve did come with the power reeds installed but I have since installed the pro series reeds as thats the only choice at this point.:( They might end up being the best choice anyway but it would be nice to have a choice. Does anyone know if any changes have been made on the kdx rad valve over the years? One thing that I did notice is that the intake has an ID of 35.75mm which makes for a slight restriction with a 36mm carb and will be even worse with my 39mm carb. I am going to machine a slight taper to the intake to smooth this transition point.
As soon as I try out a couple more jetting combo's in the woods with my modified stock carb I will be hooking my bike up to a chain driven brake dyno to try some new parts and ideas including the bigger carb, there is quite a bit of setup involved so swapping bikes around would not be to easy. This summer I will be doing some runs on a Mustang dyno which is wheel driven and I am always up for more testing, I will keep you updated on this.I get in trouble when I have my street tire on my bike, it is way to tempting to take a blast up the street. Wheelie city! I have a couple dozen runs on a dynojet dyno with my bike and have the dynos database with over 1600 runs from all types of bikes. I have the winpep software on my PC so I can compare ( for what its worth;) ) my kdx to quite a few different bikes . --Dan
Since you're on the subject I thought I'd share what I learned the other day when talking to a boyesen rep. I was asking what the difference was between the rad-12 (for the KX) and the rad-12x (for the KDX). He said it was mainly the size of the bore (the KX being bigger). He also said with the way a stock KDX breathes, he wouldn't recommend a swap but hasn't had a experience with a modified KDX. Bummer cause I know where I can get a brandy-new KX Rad for $100 bucks. I also noticed the the old Ram valve in my KDX had been "ported" by a previous owner.
The Boyesen catalog lists the 12x for the KDX250. It lists the 14xa for the 200-220.
Regarding flow in general and bored carbs in particular....
Any abrupt change in volume of parts is going to cause a turbulence problem. You'll end up with all sorts of swirls and eddies in the airstream that would lead to a subtraction from any rareified process already accomplished by upstream 'ductwork'. You'd have more of a problem with a mismatch of mating surfaces than you would slight volume changes. The swirls and eddies and associated pressure changes cause fuel to drop out of suspension (if your lucky enough to have it really atomized in the first place)..and any fuel not going where it's supposed to is obviously a problem.
That being so, I wonder if there is anything to worry about with a 35.68mm rad valve and a RB modified (bored to 36mm) carb because the plenum divider is going to take up some of the 36mm.
It's NOT always true that bigger is better. There's something to be said for velocity and ram effects of smaller air passages. The harmonics involved particularly in 2-stroke engines intake tracts will have a more pronounced effect on a smaller area, too.
39mm is a different issue altogether. Dan...time to get out your modification tools to divide and conquer this problem as you have others.
Wouldn't you think boyesen would put their stuff on a flow bench rather than just come up with something that fits a particular bolt pattern? I'd hope so.
I have a Holley 4779S that I need a manifold built for. I think the 'double pumper' option of that carb would work great on my 200 scooter!