RAD Valve Survey

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Mar 6, 2001
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#1
I'm toying with the idea of doing either the RAD valve install OR the RB Designs carb rework. I have the oppurtunity of getting a RAD valve assembly this weekend from some very knowledgeable/cool KDX folks( U know who U are :-) which wouldn't require taking my bike out of commission. OR going ahead and figuring out what the program is with RB Designs in removing my carb and shipping it to them, I don't know what their 'normal' turnaround time is but it could possible affect my next weekend riding plans. I've read Canadian Dave's reveiw on the Boyesen RAD valve in the Just KDX Hop-Up Guide and chatted with a couple of other folks about RAD valve usage. My 2-stroke knowledge is very limited so wanted to access a larger cross section of KDX owners that have a RAD valve installed and ask...... " Would you do it again knowing what you know now??" I have a 1996 KDX with a 240 kit, Boyesen reeds in stock reed valve holder, Gnarly torque pipe and a Pro Curcuit silencer. I love the bike as it is but would like to do something that might enhance the low-mid range torque. So would like to hear from KDX owners who have 'been there/done that' regarding these options! Thanks in advance for your imputs. Happy Riding!! CD

PS. I tried doing a search on 'RAD valve' and didn't come up with anything from the KDX forum yet I'm betting there is tons of info buried in the archives. If you have the links to those threads I would appreciate that also!!
 

Sage

dirtbike riding roadracer
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#2
do both, i've got a rad valve & a plated carb and it works very well, all around. if the compression wasent rasied with the 240 kit milling the head down to get 190-200 psi of cylinder pressure will help also.
 

KruncH

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#3
I agree, do both. My setup is '98 200 Fredette ported, rad valve, RD carb mod, FMF rev & TCII. Here's the order of my upgrades.

1. The bike came with the torque pipe and TCII, I replaced the torque with the Rev.
2. Added the rad valve
3. Got it ported
Lastly, the carb mod. Each piece contributes to the whole. I could feel the difference at each step. I just always wanted more. Just when I "thought" the bike was ripping, I'd do another upgrade and wow, hold on tight. If you have the $$$ for all of it, than go for it. In hind sight, if I had to only pick two of the above mods, it would be the pipe and the carb mod. Don't get me wrong, the rad valve and the porting pushes the rpm range way on up there extending the power band quite a bit. I don't ever regret getting them done.

Hope this helps :)
 
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#4
Maybe a flywheel weight??

Thanks to Sage and KruncH for your imput on the RAD survey question I posted! Sounds like the RAD valve is more of a higher RPM air/fuel flow improvement vs. low end torque. I guess that I am looking for the low-mid range torque increase and am now wondering if a flywheel weight might be a good addition for increased tractability in slow speed rock riding. I would be curious as to who is a preferred supplier of a flywheel weight and what size(ounces??) is preferable........cost?? Does it involve having to rebalance the crankshaft assembly or is it just a "bolt-on"?? Thanks in advance for sharing the knowledge as I am certainly a newbie to the 2-stroke world, but it is fun learning!!CD
 

Canadian Dave

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#5
Hi CrashDoc,

For your money you're going to see a much bigger bang for your buck from the RB Designs carb mod. From your description it sounds like exactly what you are looking for. You'll see a dramatic increase in bottom end throttle response; it’s much cleaner. Its particularly useful in thigh, slick conditions where traction is at a premium and wheel spin can be your worst enemy. With the carb mod done you'll be able to run a gear higher than what you might normally and lug the engine to prevent wheel spin then when you need a little extra boost just roll on the throttle and off you go.

You can get bolt on flywheel weights that thread into the flywheel. There is no rebalancing etc required. I'd go with the carb mod first and take things from there.

Turn around time normally good from RB. Spring is here so Ron will be really busy so I'd give him a call and get a feel for what kind of turn around time to expect.

David
 
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#6
RB Designs Contact Info??

Thanks Canadian Dave for the info and I would like to contact RB Designs. I'm probably not looking in the correct place(might be right under my nose :-) but did a search for 'RB Designs' on Google and DRN and didn't find a readily apparent website or contact information. It has to be close by on this site, since the mod. is referenced so much here. Thanks in advance for the contact info. CD
 

Mikeb

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#7
Hopefully it is not too late for my 2 cents worth here but I agree with Dave the best bang for your buck would be the R+B carb mod. The R+B Designs website is http://home.sprintmail.com/~captron/

I have a RAD valve and had Daves modified carb this winter and the difference in the RAD valve and stock reeds was mild compared to the difference in the modified and un-modified carbs.
 

eldrm

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#8
i'd check out a flywheel weight, put one on mine and it really made it pull nice in tight rocky stuff,very easy t put on too.steahley makes an 11 ounce for the kdx i think they're about $100
 
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#9
Well the carb is enroute to RB Designs thanks to Canadian Dave and Mikeb's imput. I had a nice chat with Ron @ RB (very pleasant/helpful/knowledgable) and his turn around timing is great right now so I won't miss a weekend for riding! I wondered if 'eldrm' might have a link to access the company that sells the flywheel weights?? Your imput on that sounds interesting! Thanks again for all the imputs, I'm really looking forward to getting the mod'd carb back and taking a ride!! CD
 

acutemp

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#10
CrashDoc, My kdx is setup pretty much the same as Krunch and MikeB. IMO I would hold off on the flywheel weight until you get your carb dialed in. I real doubt that you will be needing one with the setup that you will have. Like Dave has said you should see a much improved pull off the bottom. I have a 10oz steahly flywheel weight that I got after I had my porting done to help calm the hit a bit in the tight woods . I only ran it maybe 25% if the time and it did help in the slick stuff but I have yet to run it since I had my carb modified and that has been over a year now. Good luck with your bike and be sure to keep us posted on how it works for you.--Dan
 
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#11
for anyone intrested i have a rad valve for sale, i had it on the bike just for a week, i didnt like how it made the bike feel, its in like new condition and i want just 85 bucks for it plus shipping, its to fit a 97 kdx 200 but i think it will fit all kdx's from 95' to 01' im not sure if it will fit 220's though, its a pretty smokin good deal because i think i paid like 150 bucks for it.:eek:
 
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#13
Digging the RAD valve: NOT??

That is a interesting testimonial to the non-usage of a RAD valve, joe ! I guess that considering the other post about how well your jetting is working the RAD is going into the memory pile! I am curious as to what it actually did (engine response) that didn't "feel" correct and at what RPM range; low/mid/high?? Interesting!!?? CD
 

eldrm

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#14
crashdoc-i don't believe they have a website yet, but here is some other info that should help...
steahly offoad products inc.
3850 pioneer rd.
meford or.97501 1-800-800-2363 1-541-535-4896
 
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#15
its hard to explain, it made the throttle twichy, not sure if thats the right word, for a mx bike i think it would be great, but im more of a woods rider, after riding my bike this weekend i have things setup ideal for the riding i do, that is not to say it would be good for everyone, this whole bike tunning thing is experamental, and i just think for me a rad valve is not needed, just wish i knew that before i sepnt the money for it.