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Airbox Mod, How-To

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got home from work this morning and pulled the carb off mine. seems like the previous owner did some tinkering himself. the cover was off of the side of the airbox and the pilot screw plug was already drilled.

upon further inspection i checked pilot screw position and jets to see where i am at.

pilot screw: 3 full turns out

pilot jet: #42.5 Mikuni jet

Main jet: #170 doesnt apear to be genuine mikuni, has no taper in bore

Needle is def not stock and was shimmed. ill post some pics of the needle and see if anyone recognizes it. right now its sitting next to my micrometers and vernier. in the next couple days im gonna take as many measurements as i can and then draw it up in CAD.

needlesideview.jpg

needlebottomview.jpg

needletopview.jpg

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Holy Moly there YZDR! That looks like a DJ needle with the stock plastic spacer. Compare lengths to my post on the needles. If that is the DJ needle get that spacer out of there. :censored: That thing would be crazy rich if it is the DJ.....

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thats what i was thinking... ive only ran it once and havent really ridden it yet, but it seemed really rich. plugs are carbon black. anyway i finished mic-ing it out and drew it up in PRO-E. :censored: heres the pic:

needlesmaller.jpg

PS if you want any dimensions of any sort lemme know i can create a 2d drawing with whatever.

Chris

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PRO-E is cool. We use it where I work....... OK. I don't use it.... "It's used where I work" would be the proper statement. :censored: A PRO-E drawing of all four needles and the dimensions would be awesome! I'll be updating my DR650SE Needle Comparison post once I get back to San Diego and finish the measuring and photo session. Maybe if you had the time you could take that info and do a PRO-E drawing of it? :ride:

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yeh i could do it.... i took measurements every 5.62mm which gave a pretty acurate representation i feel.

Chris

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Posting here to link to the DR650 needle comparison thread. Can we try and measure the needles the same way that Mikuni specs their measurements? I've found a link with Mikuni needle specs and have a PDF file of the Mikuni Carb Manual that give the Mikuni measurements.

More info in the needle comparison thread...

http://www.thumpertalk.com/forum/showthread.php?t=467615

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GA thumper... thats the beauty of drawing that up in PRO E.... i can take 6 or 7 measurements, create the drawing and then from there make an analysis of whatever points needed to get a cross referencable needle. i will work on taking MX robs numbers and make some drawings of those too and post back in a day or so with results

chris

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Bikesmark, I agree with you in the sense that I'm not looking for any huge gains. I just want to get the surge out of it and get it to run cooler. Right now, when just cruising the neighborhoods and backroads at slower speeds, it surges BAD!:censored: I truly love the bike, it just needs a little fine tuning to make it smoother and cooler.

I don't want power gains and don't want to lose much MPG (currently average 52mpg and would tolerate 50mpg). But I do get occasional popping/backfiring and if running a bit richer would help longevity, I'd consider rejetting after my warranty is done.

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GA thumper... thats the beauty of drawing that up in PRO E.... i can take 6 or 7 measurements, create the drawing and then from there make an analysis of whatever points needed to get a cross referencable needle. i will work on taking MX robs numbers and make some drawings of those too and post back in a day or so with results

chris

That would be sweet! :censored:

I was hoping for those cool pro-e drawings of all the needles.

Thanks for helping! :ride::lol::applause:

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I don't want power gains and don't want to lose much MPG (currently average 52mpg and would tolerate 50mpg). But I do get occasional popping/backfiring and if running a bit richer would help longevity, I'd consider rejetting after my warranty is done.

Personally I wouldn't wait until after the warranty. The jetting will be way too lean from the factory. Have you ever noticed your header pipe at night? Mine was glowing red for about 6-8 inches from the head! :censored: They do this to meet EPA standards for emissions.

Even if you just drill out the idle jet plug and turn out the idle adjustment a bit it will help the bike run better and run cooler. You can certainly get away with the stock main jet with no airbox mods and no aftermarket pipe. The main only affects about 3/4 to wide open throttle anyway. I would do this now, and then if you want to wait until after warranty...

I can't emphasize how much difference it made to my 650 to let her breath a little better. I didn't remove the airbox cover, or cut or drill the airbox, I just removed the rubber snorkle, drilled and adjusted the idle jet, installed a K&N filter and increased the main jet. (I did install a Yoshimura slip-on exhaust, too) It went from a pretty good running bike that you could feel the torque of the large displacement engine to a rip snorting, fire breathing, ground pawing, beast. In my opinion, now it's how a 650cc dirt bike should run in the first place.

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yeh i could do it.... i took measurements every 5.62mm which gave a pretty acurate representation i feel.

Chris

Chris, do you want me to do another measure session on all four needles at 5mm increments for a better Pro-E profile map? I'm able and willing for the betterment of the DR nation. Besides that it would be just too cool to have accurate Pro-E image of the needles. Might even make a good poster for the garage! :censored:

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rob i can make the profiles from the measurments you took... but the more you have the more accurate the profiles will be. this weekend im tied up. but maybe monday or tuesday i can get to it.

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rob i can make the profiles from the measurments you took... but the more you have the more accurate the profiles will be. this weekend im tied up. but maybe monday or tuesday i can get to it.

Chris, there is certainly no rush... I will go ahead and do a remeasure session next week and post the revised 4-way comparison. I'm still planning on taking the measurements from the bottom of the plastic washer on the stocker and the bottom of the clips on the others. I will use DJ's standard 4th clip position for their needle and the middle positon for the Factory Pro and KTM needles since I have no clue as to a starting point with them. Hmmm, does anyone with the Factory Pro needle have Factory Pro's suggested clip position? That might be interesting to know. :censored:

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rob when you take your measurements, forget clip position. start from the very top of the needle and make measurements each 5mm.. then give me the # of clip positions and sizes. this will yeild the most accurate #s. also when you get to the end of the needle if there is a "point" at the end like the DJ give me a measurement of the Diam. just be4 it turns down into the point and then the overall length. this is the easiest way to translate everything into Pro-E language.

if you have any questions gimme a shout at (717)587-3973, cells always on

Thanks,

chris

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rob when you take your measurements, forget clip position. start from the very top of the needle and make measurements each 5mm.. then give me the # of clip positions and sizes. this will yeild the most accurate #s. also when you get to the end of the needle if there is a "point" at the end like the DJ give me a measurement of the Diam. just be4 it turns down into the point and then the overall length. this is the easiest way to translate everything into Pro-E language.

if you have any questions gimme a shout at (717)587-3973, cells always on

Thanks,

chris

OK, I'll do that for the Pro-E measurement images. For the comparison I'll use the clip position as I'm trying to relate throttle position to needle diameter. Using top of the needle measurements on the stock and DJ needles in the comparison will throw into the numbers. The area above the position that the needle rests on in the slide, either on the DJ's clip or the stocker's plastic spacer, is completely different on those two needles as can be seen in the 4-way comparison picture. Measuring from the top of each needle would give us uncomparable operational needle diameters at a given throttle setting. :applause:

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Measuring from the top of each needle would give us uncomparable operational needle diameters at a given throttle setting.

obviously.... the point would be to have the accurate drawing in Pro-E and be able to do an "analysis" of the needle in pro e to get the exact diameter at a specified length

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obviously.... the point would be to have the accurate drawing in Pro-E and be able to do an "analysis" of the needle in pro e to get the exact diameter at a specified length

Please know I meant no offense in the above "lame" posting. In retrospect it was a "lame" addition to the statement and I apologize if you took offense. My main point is that the run of the mill over the counter Mikuni needles in a given series all have the exact same profile in the clip area but the DJ and OEM DR needle do not so measurements taken from the top of those needles would produce confusing numbers.... that's the LAME I was trying to imply. :applause:

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A friend just gave me some specs on his DR carb mod. He's claiming better performance than the Dynojet mod and with much better fuel economy (50 - 55 mpg). He claims that the Dynojet needle is too rich.

He opened the airbox, turned the fuel screw 2.5 out, added the K&N filter, and put a 160 main jet in with the stock needle (no shimming). He has 2 DR's one with the Dynojet Kit and one with this mod. That's all I know about the mod.

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