does anyone run a carbn fiber aribox???

25 replies to this topic
  • BBRguy

Posted January 27, 2001 - 12:23 PM


hey im curious, cause i wana get one, it saves about 2 pounds, and supposedly adds around 2 horsepower ( the DSP Henry replica does) and its about 500 bux...not bad for something that can give me power, and a weight reduction, not to mention a high weight reduction...anyway. yall let me know if its worth my money. see ya.

  • MXOldtimer

Posted January 27, 2001 - 01:31 PM


At 250 bux per pound thats not that great a deal, how about buying a jump rope shed 2 lbs for about 2 bux. You'll save weight, look better,live longer and lower your center of gravity at the same time.


  • MrMXer

Posted January 27, 2001 - 02:47 PM


I'd like to run one, but not for $500. I'd say there are cheaper ways to gain 2hp. But if it's a status thing your after.. Carbon fiber and Ti products kinda says it all.

  • MrMXer

Posted January 27, 2001 - 02:47 PM


I'd like to run one, but not for $500. I'd say there are cheaper ways to gain 2hp. But if it's a status thing your after.. Carbon fiber and Ti products kinda says it all.


  • aag800

Posted January 28, 2001 - 05:12 PM


I bought my bike used from my friends dealership and it had one on there. After I took the bike home and tore it apart, I went back to the shop and swapped the airbox for a stock one off another used bike. The thing is such a piece of @#*%!!! There was fiberglass resin chipping loose inside the airboot(on the carb. side!). The surface that the filter mounts to is just a flat piece of flimsy carbon fiber with no lip. There is no port for the fresh air valve and so on and so on.... Basically I would not waste $500 for a substandard product no matter what the advantages are! Go buy a pile of tires with your $500, you'll appreciate them more!

  • holeshot

Posted January 28, 2001 - 06:26 PM


Two extra HP from a carbon fibre air box?

I have some Ocean Front Property in Arizona that you might be interested in.

  • BBRguy

Posted January 31, 2001 - 08:12 PM


ha ha thanx guys, im not gonna buy one, i guess the only reason the factory's run em, is cause they can, and they get free ones if they chip or i liked MXoldtimers sugestion the best..funny stuff.thanx guys, see ya.

  • BBRguy

Posted January 31, 2001 - 08:12 PM


ha ha thanx guys, im not gonna buy one, i guess the only reason the factory's run em, is cause they can, and they get free ones if they chip or i liked MXoldtimers sugestion the best..funny stuff.thanx guys, see ya.

  • kevin6n

Posted February 01, 2001 - 02:41 AM


I bought a used YZ400F from this dude that bought 2 Vipers because they came in 2 colors,2 Hummers (1 he left stock & drove on the street and the other he super charged & tricked out for off road), and a drag boat with a parachute for brakes, (he's had it for 2 years and never had it wet).
I could go on & on, but my point is.. yes it has a WOW factor of 10... and I've never rode the bike with the stock box but I would go for the tires instead of the box on my budget.

P.S. I'm not satisfied with the power right now (no consistant hole shots but wins are consistant...I'm selfish I want it all) and will be looking into the cam timing & valve adjustment today.
I will also be testing with the Factory R&D pump bowl, and difrent jetting specs. Also when I get it breathing fire I'll test with the two air boxes and post the seat of the pants diffrence.

One more thing concerning weight, this bike has everything carbon fiber, titanium and gold talon on it you can buy with [STUPID] money and it is still heavy, but the cornering, flight and power delevery characteristics of the YZF schreds 2 strokes.

kevin6n... from GA.

  • BK

Posted February 02, 2001 - 08:09 PM


Hi Guys,
I have some answers concerning the DSP carbon fiber airbox. The reason it adds power is because the intake runner is 90mm shorter than standard. The weight savings is definitely an advantage though. The first gen. airboxes were a little rough but I think the new ones have much better quality. The power is definity moved higher in the rpm range. $500 is a lot of money and it could be spent in other places of course. But when weight savings is everything it becomes a moot point.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Taffy

Posted February 03, 2001 - 12:10 AM



what do you mean, the intake runner is 90mm shorter?

i put the increased power down to the increased volume. especially if it's top end. i figure that there is a resonance between the air filter inner face & the carb but, outside it i think the airbox is simply too small. on roadbikes they talk of how many litres an airbox holds & in the 80's & 90's they all went daft & produced these huge capacity airboxes. did the trick though!

let us know.


  • BK

Posted February 03, 2001 - 11:35 PM



First, whats with the slam on the previous post? I didn't quite get the joke.

Anyway, inside the intake boot there is a funnel shaped flare, similar to a velocity stack on hot rods. This is a tuned length intake and it is very important. It has to do with intake harmonics. It is timed to an inlet pulse and is tuned to engine speed. The stock airbox boot is approx. 120mm long. The DSP carbon fiber airbox has a velocity stack built in and it is approx. 40mm long. The shorter the length the more the hit the midrange will have, the longer the length the smoother the midrange will be.
The 250F is especially affected by the short length of this airbox.


  • Scott_F

Posted February 04, 2001 - 08:02 AM


BK, can you elaborate on the effects on the 250F? It seems the DSP box has different velocity stacks for each bike. Do you know if the stock airboot is identical on the 426F and 250F?

  • Taffy

Posted February 04, 2001 - 11:23 AM



we've had to guess the valve timinng. nobody could find out even the standard settings.

the joke?

in 'all the presidents men' RR has to keep meeting a guy in the shadows of an underground car park. he only says they are on or off the right trail & getting warm etc.

i hope you see the connection. helps to have seen the film as well!

a question.

i feel the 42 PJ should go with 100 PAJ
45 PJ should go with a 110/120?
48 is unnecassary if you have 45 set-up as above? but certainly needs a 120+ PAJ.

any factory info on this please.


  • James_Dean

Posted February 05, 2001 - 04:15 PM



(This is a '00WR with YZ cam timing and YZ exhaust)
Last summer I tried pilots 42,45,48, and 50. The 45 and 48 were run with #75 and #100 pilot air jets.

-The 45/100 combination worked well when the carb needle was set richer. This is close to the 45/110 you questioned. This ran very clean at idle. This is the direction you are pointed.

-When the needle was on a leaner clip the 48/100 pulled stronger from idle and also made for easier starting. The pilot screw needed to be at 1 turn or less. Because of the easy starting and tractor torque, I prefer the 48/100. (My plug may be darker at idle for it though)

-Note that ALL the KTM 4-strokes are using a #48 pilot and #100 pilot air. These start incredibly easy, push button or not.

-Who knows what a #120 pilot air would do- :)


[This message has been edited by James Dean (edited 02-06-2001).]

  • Taffy

Posted February 10, 2001 - 03:42 AM


ever tried a pilot air SCREW james? as in replacing the PAJ for one of these?


  • James_Dean

Posted February 10, 2001 - 12:49 PM


No, I have not.

See about this.

  • Taffy

Posted February 10, 2001 - 02:24 PM



you & clarke never quite let the cat outta the bag with your needle experiments & i respect the hard work you both put in.

there's a better needle out there yet & it's got your name on it.

from what i can gather the needle taper starts too late so you get a stutter. if you were to lift the needle one or two clips the stutter would go off idle but it would run rich at mid throttle, am i correct so far?

reading between the lines the needle could do with being thinner at the tip for a richer 3/4 throttle?

thus the three stage needle you were on about.

i think the answer is to calculate the emulsion tube to go with a wider needle straight, for idle running etc. work out where you want the taper to start, work out the third letter, THEN work out the emulsion tube to go with it using calculations of CSA. i'm not sure of the other outside effects to the tube. none i hope.

this is what yamaha are leaning (no pun intended!) towards as the third suffix is gradually rising on each model without the size of the tube going up.

the wider needle would start it's taper earlier so no misfire here.

i'm sure the 48 PJ / 100 PAJ are wrong.

the other way of getting rid of the stutter is via the PAJ & the PJ, especially they're correct pairing.

yamaha say they should go together & i believe them. i read that blokes stuff & there is more in there that i've been espousing than you are. i'm not disagreeing with what he says about the effects of the MJ on lower revs i'm saying my theory is EQUALLY true. that i stick by.

remember i haven't read a single sheet, statement or book about this for years. you said you didn't want to use a dyno coz you trust your instincts, well i feel the same way.

dyno's aren't the whole answer. they just save time. i still think you boys should have a little dynofest between you. could start a trend. everyone has to bring something & pay part. the the bike owner gets paid to thrash his bike (bless him!)

the only thing i didn't get was how he reckons that the airjets lean the mixture? whatever else they do they must do one or the other or we wouldn't have them!

i've grown up calling all this s*** "the enrichening circuit" i'm sure you've done the same JD.

the way he's talking if i put the 75 PAJ back in it'll run richer. mmmmmmmmmmmm!

i've used a PAJ-screw (can we stick to this name-it gets confusing & i don't like jargon) but the turns didn't tally. remember my aborted needle change at the manx gp last september?

i reckon that keihin in their infinite wisdom have got each PAJ & PJ overlapping. so that they sit like two rows of house bricks;

75 - 42
75 - 45
100 - 45
100 - 48
110? - 48 etc


  • Taffy

Posted February 10, 2001 - 05:30 PM



more anon

if you introduce more air into the MAJ you weaken the top end. that i'm sure you agree with.

but if you introduce more air into the low speed PAJ it draws more fuel surely?

with the former air is introduced to fuel (weakening it) & in the later fuel is introduced to air (enrichening it).

well he does say that his friend would disagree with some of his stuff.


  • Taffy

Posted February 11, 2001 - 03:05 PM


my ideas are leaning toward trying a #190 & a #210 MAJ.

the other is not to increase the PJ & leave the PAJ alone but to do the opposite.

increase the PAJ & go down on the PJ & turn the pilot screw IN.

if i get the chance i will set the WOT MJ on the road this week & then visit my local free patch at the weekend to try the PAJ-screw again.


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