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tuning carbs for tbr exhaust and bmc filter

Old 08-28-2010, 10:53 AM
  #1  
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tuning carbs for tbr exhaust and bmc filter

Hey every body

I just bought a tbr aluminium exhaust (older style) and a bmc street filter. Also did PAIR removal and tps adjustment. With no mods to the carbs the bike pulls much harder up top (form 7500-9000) to the point that I have trubble shifting in time and can fell the front end getting a little lighter then before. Down low (below 5500) there is lots of holes and stumbling and burbbles a lot on decle. the bike also idles fine.

My question is because the bike pulls better up top at full throttle is my main jet good and only my niddle hight and feul screw (i think thats what its called) that need to be adjusted? and if so can those adjustments be done without a kit?

Thaks for your help boys (and girls)
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Old 08-28-2010, 11:09 AM
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If Mike (8541hawk) doesn't jump in here soon, I'll go ahead and say do what he has recommended, at least as a start. That is to go up to 48 pilot (slow) jets and do a .040" needle shim. That may be all you need, since it's running well on top. I got the pilot jets at the dealer for $6 and change each. #4 brass washers from the hardware store, 11 cents each.

I'm running a stock air filter and the 48 pilots and .020" shim, pilot screws 2 1/2 out, is working well for me.

Isn't that little extra pull on top nice?
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Old 08-28-2010, 01:44 PM
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Follow the Factory Pro recipe a set of steps after using all suggestions given to get close"er" or in the ball park.

As i understand there is only one way to work towards "near" certainty with carbs and no dynamometer fees.
A controlled system of steps and analytic procedural diagnostic indicators...
i.e... , performance markers, signs, and real world feel=seat-O-pants Dyno, explained..
See below: link to Factory pro carb tuning for how and why this is science.

Trial and Error + years of professional experience has compiled this series of steps to maximize time spent to dial in your combo.
http://www.factorypro.com/index.htm
i am a happy customer not an owner or sales rep.

i understand there is a library of successful combinations for your bike and your options. call them have your facts handy

Factory Pro is Great tech support and real helpful, real world, and real results. There are reputable shops and tuners i dont know any.
others may have your combo and a perfect recipe get you there fast here is how you will be sure you are at peak for your power-plant
Contact Factory Pro
M-F, 9am - 6pm, Pacific time, -7 or -8 GMT

800 869-0497
USA and Canada

415 491-5920

fax 415 492-8803

parts information
[email protected]

EC997 dynamometer information
[email protected]
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Old 08-28-2010, 02:46 PM
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Nice Factory Pro ad......lol

I use a stock air filter so you may have to fiddle around a bit with the settings that VTRsurfer posted but that is the "starting" point that I use.

While Marc @ factory pro is a good guy (and I am using his ignition advance) I actually like the stock needles that come with the SH.

Also, in case you might think I'm just making this stuff up, I got the setting I use from Dan Kyle, so use whatever you like but there really is no need to spend over a $100 for a jet kit on this bike. But as always YMMV.
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Old 08-28-2010, 07:01 PM
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thanks for the advice, but I did already go to the factory pro site. That's where i got the Idea that my main jet was OK because the bike pulled better a high rpm full throttle. I think i might try going with mikes setup as a baseline and then go from there. and yes the pull up top is very nice(so that's how you spell needle lol)
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Old 08-31-2010, 08:37 AM
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Good morning,

I was wondering what the collective wisdom of the board has to say about the water hoses routed to the carbs. I assume they are there to heat the carbs. Is it best to leave them be or disconnect and plug them?

Cheers,
Roy
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Old 08-31-2010, 08:41 AM
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Another quick question....it looks like in the factory manual that there is a factory installed shim under the needle but I can't tell for sure. I bought the bike used so just don't want any surprises when I open up the carbs to add shims. I imagine over shimming would not be a good thing.....

Thank you
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Old 08-31-2010, 08:42 AM
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There is quite a debate as to the necessity or effectiveness of them. Some will say it aids in fuel atomization to leave them on while others claim it makes the fuel hot which leads to poor mixture. A few have done some tests and I believe the results were inconclusive with most agreeing there were no gains to be had. Search for the threads and you'll be able to read all about it. I for one don't fool with them and leave them as is.

Last edited by RWhisen; 08-31-2010 at 08:45 AM.
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Old 08-31-2010, 08:51 AM
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Thanks for the info, think I will leave mine alone for now.
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Old 08-31-2010, 01:45 PM
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On a completely stock carb will there be just a needle with a clip on it with no shims of any sort?

Thanks
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Old 08-31-2010, 02:45 PM
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There should be a shim on if untouched stock... Just like in the parts fische... But that's not counted as a "shim" when you tune stuff as it's the baseline...
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Old 09-10-2010, 05:01 PM
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[QUOTE]There should be a shim on if untouched stock... Just like in the parts fische... But that's not counted as a "shim" when you tune stuff as it's the baseline.[QUOTE]

So what your saying is the washers on the stock needles are the starting baseline for tuning the carbs,

in short leave the little guys in there
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Old 09-10-2010, 05:10 PM
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Yep...
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Old 09-15-2010, 10:56 AM
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Where does a person purchase #48 Pilot jets? I contacted a Honda dealer but they have no listing for such an animal....help!
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Old 09-15-2010, 08:33 PM
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Old 09-15-2010, 09:00 PM
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and before you ask...... you are looking for a N424-21 series pilot (or slow jet) and buy the real thing, don't go cheap and buy the "equivalent"
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Old 09-16-2010, 12:46 PM
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Thanks for the info! I also found through spending way to much time playing around with cross referencing that a 1998 Honda XR250R also uses the same pilot jets and offers a range of sizes in your typical parts fiche look-up. The Honda part number I came up with is a 99103-437-0480. But I have to admit the jetsrus.com option sounds a lot easier!

Cheers,
Roy
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Old 09-16-2010, 01:04 PM
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Jets ordered from "jetsrus" and on their way....thanks again guys!

Cheers,
Roy
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