Ron Black

Questions and Answers about the best carb and Head mods available for the KDX.
johnkdx220
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Post by johnkdx220 »

Just checked http://www.DHL.ca ... Looks like DHL is providing coast to coast service in US & Canada. Why? Are they better than UPS? Will RB do business with DHL?

GS wrote: "I am no fan of UPS....in fact I typically just decline to buy if I have to subject myself to the crap they bring to the transaction...." 100% agree! ... but the RB mods seems to good to resist!
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Post by Indawoods »

DHL is dirt cheap compared to UPS. The new kids on the block is looking to take UPS's biz.

It'd be worth checking out....
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Post by canyncarvr »

DHL could have had a delivery in Canada for 1-1-07 EARLY a.m. ....and they wouldn't be there yet.

Consider the source
Using a perceived level of knowledge to boost my self worth.
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Post by Indawoods »

:blink: Whatever that is supposed to mean....
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Post by GS »

The trick may be to get the shipper to use DHL. I have no idea how reasonable they are cross-border.

BUT, they couldn't be any worse !

It certainly sounds like RB's handiwork is worth the shipping hassle!
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Post by skipro3 »

John, keep in mind I can 4th gear wheelie because I had my head set for race gas and my jetting is on the razor's edge. That means I used the AirStryker modded carb to get to that point. Not a modded stock carb. You would have to pay duties on the new carb.
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Post by Jeb »

>|<>QBB<
skipro3 wrote: . . . I can 4th gear wheelie because I had my head set for race gas and my jetting is on the razor's edge. That means I used the AirStryker modded carb to get to that point. Not a modded stock carb . . .
I'm glad you brought this up!

So there's even better performance with the modded Airstryker vs. modded stock carb?! I mean, comparing the two if both had "razor-edged jetting"? I'm not sure about 4th gear wheelies on mine - which has the race gas head & modded stock carb - but only because I just don't do wheelies in 4th gear. But then again, maybe my current mods don't get me there and I just don't know it. Whatever the case, you got my attention!

I feel a warm fuzzy coming on . . .
Last edited by Jeb on 05:36 am Dec 11 2007, edited 1 time in total.
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Post by johnkdx220 »

Skipro: With a razor-edged carb and top-end, did you have to strenghten the bottom end (Wiseco crank required?) I guess I should ask how much more compression and RPM did you gain with this razor edge configuration?
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Post by fuzzy »

No bottom end mods necesary to run a race-gas prepped top-end. As far as I know there are no aftermarket cranks for the KDX (maybe better rods, but again not required). If there was one, it'd be a stroker, and that would be SAAAAWWWWEEEEET! A 215-225 w/ 200 bore/porting, but longer stroke would be the ultimate.
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Post by skipro3 »

I'm unable to compare a well jetted KDX that has the modded stock carb to a well jetted KDX with a modded airstryker carb. I've only had the one with the airstryker carb.

To further define a 4th gear wheelie, what conditions were:
Slight uphill grade on a paved road. Running up through the gears, and cranking on the throttle to loft the front wheel without any body english to assist in 2nd gear. As soon as the front end gets up to about 2 feet off the ground, I would shift using the throttle backed off slightly, then back on the gas just below full throttle; 3rd gear lofts up sweet as pie with no body english, just sitting on the saddle. Same for 4th gear; back off throttle, shift, gas it hard to just a hair shy of full throttle and the front end comes up. Going fast now, and running low on room as well. Never have to tug on the bars or anything to get the front end up other than I'm on a gradule uphill grade during the process.

And like Fuzz said; no need to beef up the bottom end because it's so strong already. Most if not all bikes are. Jetting makes a big difference. Spend the time needed to do plug chops. When it's right, the bike will take on a life of it's own!!

Right now, I don't have the KDX but I've got my KX250 jetted for a strong bottom end right off idle. It doesn't hesitate but it also doesn't snap and spin the tire unless I'm up into the KIPS valve doing more than 6 or 7K rpm. Then it hits hard but I also loose traction. Ron tells me that it's probably not worth the money to mod the KX250 carb or reconfigure the head since it won't be as dramatic of a difference.
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Post by Indawoods »

I've had 4 gear wheelies on my last ride due to a perfectly jetted modified carb. Suprised the hell out of me...... and my brother. It was ZEN! :supz:
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Post by fuzzy »

Ron tells me that it's probably not worth the money to mod the KX250 carb or reconfigure the head since it won't be as dramatic of a difference.
Really? Don't think it would help w/ pulling the tall 1st gear (in idling situations)? I can tell you one thing that helps....a 36mm carb....Take a look at what the wide-trannied KTM 250/300's come with these days. A slight hit up top is not signifigant to a woods-guy.
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Post by skipro3 »

>|<>QBB<
Indawoods wrote:I've had 4 gear wheelies on my last ride due to a perfectly jetted modified carb. Suprised the hell out of me...... and my brother. It was ZEN! :supz:
Jetting makes a world of difference doesn't it!! :supz:

Most folks are afraid to lean out and seize but it's been my experiance that during a plug chop test that the bike will tell you when you've gone too far with some pinging noise well before you will seize the bike up. I really liked playing tag with my bud's KX500 on fire roads anything under 50 mph and not too much straight aways and he had to work hard to stay in front of me.

Fuzz; yup. that was what he told me. He said he'd be happy to mod a head and the carb and told me how to measure my squish using some solder to do a press. He needed the solder press as a gauge to measure the current squish. He basically said that the change would not be as dramatic as with the KDX. I'm guessing that the KDX is so mildly tuned in comparison to a KX that he has much more room to play with improvements. With all that and being happy with my KX and it's power valve on the carb, I'm just going to stay with it. As far as the 36mm carb goes, I'd think the divider plate in a 38 would be the ticket. I might still pick up a carb off eBay and let Ron give that a go just to see. Soon as the holidays are over and I have some extra cash to bid on one, I'm going for it. I already have a spare head as well. Might have him give that a try for my next top end overhaul just to see for myself.
Shaving the base on the cylinder is another trick where you can lower the port timing to boost bottom end performance. I talked (e-mailed) Ron about that as well. He's very amicable about talking about such things, just wanted to caution me on the KIPS timing and the piston crown clearances if I remember right.

Tall first gear:
It is only a problem for standard clutched KX's. My autoclutch isn't affected. I just dropped the CS sprocket 1 tooth and she' a crawler now.
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Post by Jeb »

Even a little bit of an incline helps with wheelies. And a moderate incline makes it hard to keep the front wheel down on my 220, that's for sure.

I know I've certainly been surprised with the front wheel lifting off the ground. When I'm on the throttle the front end gets real light. I remember the last time Rick, Andy, and I rode early this past September, Rick took a spin on mine (I was interested in his impressions of the race gas head). Rick opened her up in the open and I was amazed at how often the front wheel was lifting off the ground - like each gear change. Maybe Rick will read and comment.

Under the crisp jetting, slight hill, etc, etc conditions I just may be able to loft the front wheel in 4th.

So . . . what ARE the advantages of the Airstryker? I've read a few posts but didn't get much out of it other than the A/S was less sensitive to temp/altitude conditions (more "robust" I believe was stated).
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Post by fuzzy »

SOunds good Ski. Yeah, the heads are cut a lot tighter on the MX motors. They should need every bit of 91, and probably 93 for desert flogging....THe KDX can probably run on 'good' 87-89 stock. Problem being all the low-octane gas sucks. Yes, I'd be really curious as to how a RB'd 38 would perform. The-low speed mods have to be great! You've got a good point though you probably don't notice all his magic as much w/ the autoclutch.
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Post by TWMOODY »

I just got the Race gas head and AS and have not had a chance to try out
yet however my bike will easily lift in 4th gear on a flat and if you hit the kips right will lift in 5th also. My current set up is R&B modded OE carb
desert pipe, TC2, vf3 dek 4 42/152 and 13/48 gears.
I do not use the factory set up for kips gear timing
I set by EYE and I trimmed the cylinder side of the kips valves because
there will always be a slight restriction on both valves when fully open.
The restriction is proly a matter of a couple of mm which can be see by
the eye if you have the cylnder off and manually open the kips.
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Post by Jeb »

>|<>QBB<
TWMOODY wrote:I just got the Race gas head and AS and have not had a chance to try out
yet however my bike will easily lift in 4th gear on a flat and if you hit the kips right will lift in 5th also. My current set up is R&B modded OE carb
desert pipe, TC2, vf3 dek 4 42/152 and 13/48 gears.
I do not use the factory set up for kips gear timing
I set by EYE and I trimmed the cylinder side of the kips valves because
there will always be a slight restriction on both valves when fully open.
The restriction is proly a matter of a couple of mm which can be see by
the eye if you have the cylnder off and manually open the kips.
First off, you're gonna love that race-gas head. 'Looking forward to hearing what you have to say about it. This is probably asking a lot, but it would be interesting to see what the difference is between installing the race gas head only and testing THEN replace the RB-modded carb with the AS carby. I'm interested in the AS but only if what it adds is appreciable.

Second, I'm interested in what you're doing with the KIPS "valves". What exactly are you doing if you don't mind elaborating? Does what you're doing include the exhaust valve at all?

I'm getting ready to modify when the exhaust valve opens by replacing the kips actuator spring down in lower end with a spring with a lower rate. Idea is to open the valve a little earlier. OR I'll replace the governor weights (balls) with some that are a tad heavier if I can find them. Should be doing this late Feb / early March.

Thanks!
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Post by TWMOODY »

>|<>QBB<[quote="JebSecond, I'm interested in what you're doing with the KIPS "valves". What exactly are you doing if you don't mind elaborating? Does what you're doing include the exhaust valve at all?


I wished I took pics when I did it.
With the cylinder off the engine turn the kips gear fully clockwise and look at the 2 exhaust valves through the cylinder.
They do not open 100%.
You can still see the sides of the valves thus creating a small restriction
and not gaining the full effect of the kips system.
I took each valve out and used a high speed cutting disc to remove
enough material thus removing the restriction.
I only took off a couple of MM and used a fine file to smooth out once
I had the proper clearance.
Also when setting the actuator to the center shaft I leave the actuator shaft relaxed and turn the center shaft clockwise just to the point where
it opens the back it up one tooth and lock down the actuator shaft gear.

Will give a report on the gas mod then AS
I just put the head on last week but still have snow so I can't do any
reports that mean anything.
Also have my forks torn down doing gold valves.
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Post by riggy »

I just recieved my carb and head from ron . went riding yesterday the bike had real good throttle response through all gears . a lot snappier getting on and of the throttle . a nice upgrade . Thanks , Ron excellent service as well ..
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Post by RD400Fvantucky »

I live 20 minutes from Ron. I have a 1979 Yamaha RD400F aircooled two stroke street bike that uses a graphite head gasket. I also bought some 2003 KX85 PWK28mm carbs to replace my 28mm 1972 R5 350 yamaha carbs. Ron has built my crank and my top end twice. Ron has modded the PWK carbs so that the idle screws are outboard on the right side carb (inline twin motor) and put a hex allen head on the end of the airscrews to adj. with a custom made tool a.s. tool..stock nozzle replaced with a sudco nozzle. Ron has massaged the passageways of the carb also. Delron was used on the intake bell to increase it's size from 49mm (1.929") to 2" to find a popular uni foam filter to fit. Also there was a gap in the manifolds where the carb didn't fully seat. Ron made a Delron insert to fill that gap and it sticks right inside the intake manifold. My daytona one piece head was cut in 1/2, squish band/volume/angle set for popular Pro-x pistons (cheaper than OEM!) and cylinders modified for silicone o-rings. He also cut a surface for an exhaust gasket to seal my exhaust better.

I can tell you i was blown away w/ how much cooler the motor ran (squish / o-ring head mods) and the smooth even deceptive power it makes (135 psi both sides). This is preport. My main before the port job was a slightly rich 155. AFter, I'm finding it wants 150~152. 42 pilot from 45 pilot. right now @ 5/8ths w/ 42 (possibly as low as a 40), JJJ needles (experimenting with 3 and 4th clip). These are not final settings yet, but i am very close and if this doesn't work, Ron now has the needle jet holders and drillbits to modify a few things and many different approaches to reach the same goal jetting wise.

A guy in colorado at 6000 ft is running a 155 main jet (no head mods). I'm at about 600 feet and running a 155 and was richer than the guy in colorado! (comparing plug chops) This was pre-port and we had very similar mods. He didn't have the head mods.

Just another big shout out for Ron. Excellent stuff.

:supz:
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