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Thread: Jetting Database

  1. #1
    Member Ryan's Avatar
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    Information posted by ~Dee~

    My typical reply to jetting questions:

    (1) Check your intake boot for leaks!
    (2) Check for cylinder leaks since head has been shaved.
    (3) Are the reeds in good condition?
    (4) How does your plug look?
    (5) If your carb is pissing fuel the float is not set correctly.

    Many people say this:
    air screw - idle to 1/16 throttle
    pilot - 1/16 to 1/4 throttle
    needle - 1/4 to 3/4 throttle
    main - 3/4 to WOT

    BUT the range of the jets actually overlap.

    Air screw - off idle to about 1/4 throttle
    The air screw meters air to the pilot jet

    pilot - 1/8 to 1/2 throttle (changes to pilot affect the needle and main jet settings since it adds adds fuel during the midrange and topend)

    needle - 1/8 to 3/4 throttle
    an actual needle change will affect 1/8 to 3/4 throttle
    clip changes afffect 1/4 to 3/4 throttle

    main - 1/2 to full throttle


    I saw this posted a couple sites and I think it would be an excellent addition to this site!

    Each post should contain the following information:

    Mixture ratio and fuel:

    Carb Type: Mikuni, Keihin (PJ, A/S, etc.) (what bore is the carb?)

    Main Jet size:

    Slow (pilot) Jet size:

    AirScrew (number of turns out):

    Needle (what groove is the clip in, Brand, etc):

    Reed brand and type:

    Airbox: List any mods to include filter

    Pipe: What brand and type

    Engine Displacement: What size is it (250-265 etc.) and who's kit (ESR,etc) and PV or NON-PV.

    Compression ratio:

    Porting type:

    Altitude: where you normally ride
    ~Ryan~
    2005 LT YFZ 450

  2. #2
    Member Ryan's Avatar
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    information posted by ~Dee~

    My Example that has been tested!!


    Mixture ratio and fuel: 40:1 HP2 with 100RON (95 octane)

    Carb Type: 39mm Air Stryker

    Main Jet size: 160 (starting point)

    Slow (pilot) Jet size: 50 (starting point)

    AirScrew: 2 turns out

    Needle: DGH needle, middle clip position

    Reed brand and type: CR250 cage with unknown fiberglass reeds and 5mm

    Airbox: CFM Aluminum without cover and Uni filter

    Pipe: CT midrange pipe

    Engine Displacement: Non-PV CT 257cc

    Compression ratio: unknown but stock type with 21cc Coolhead dome

    Porting type: Nationals MX

    Altitude: 50ft above sea level but sometimes as high as 500ft above sea level
    ~Ryan~
    2005 LT YFZ 450

  3. #3
    Member Ryan's Avatar
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    information Posted by ~Geeker~

    Mixture ratio and fuel:

    86 octane pump gas, oil ratio about 25-35:1 premix, AF ratio probably about 16:1

    Carb Type: Mikuni, Keihin (PJ, A/S, etc.) (what bore is the carb?)

    Stock '86 Keihin PJ, bored from 34 to 36mm

    Main Jet size:

    132

    Slow (pilot) Jet size:

    35

    AirScrew (number of turns out): 3/8 from fully closed

    Needle (what groove is the clip in, Brand, etc):

    stock needle, lean clip

    Reed brand and type:

    Barnett fiberglass reeds & stock reed cage, w/o retainer

    Airbox: List any mods to include filter

    Stock, UNI w/o outerwear

    Pipe: What brand and type

    Paul Turner II

    Engine Displacement: What size is it (250-265 etc.) and who's kit (ESR,etc) and PV or NON-PV.

    Stock 250, stock bore and stroke, Geek built

    Compression ratio:

    stock (8.4:1 I think)

    Porting type:

    a little smoothing with a Dremel

    Altitude: where you normally ride

    1000-2000
    ~Ryan~
    2005 LT YFZ 450

  4. #4
    Member Ryan's Avatar
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    information Posted by ~Prednizone~

    If there's anyone out there who's bike is still a 250, this could help. tongue.gif

    Mixture ratio and fuel: 32:1 on pump gas

    Carb Type: Keihin 39mm PWK

    Main Jet size: 168

    Slow (pilot) Jet size: 55

    AirScrew (number of turns out): 1-3/4

    Needle (what groove is the clip in, Brand, etc): DGK 2nd clip

    Reed brand and type: iduno

    Airbox: none...alum. elim. bracket and uni-filter

    Pipe: CT "midrange" w/ FMF "Q" silencer

    Engine Displacement: stock...250 non-PV

    Compression ratio: stock

    Porting type: none

    Altitude: approx 1200ft (Phoenix area)
    ~Ryan~
    2005 LT YFZ 450

  5. #5
    Senior Member HiLi_Psyclez's Avatar
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    Lots of good info Thanks

    Ive Had quads, and been working on my own for quite awhile. Sometimes jetting still stumps me from time to time

  6. #6
    Member DirtStar's Avatar
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    Mixture ratio and fuel: Cam-2 (114 octane)/Klotz red label 40:1

    Carb Type: Mikuni, Keihin (PJ, A/S, etc.) (what bore is the carb?) Keihin PJ 36mm

    Main Jet size: 148

    Slow (pilot) Jet size: 50

    AirScrew (number of turns out): 1 - 1

    Needle (what groove is the clip in, Brand, etc): 3rd groove

    Reed brand and type: Boyesen Rad Valve

    Airbox: List any mods to include filter: Stock box with Uni Filter

    Pipe: What brand and type FMF Fatty with modded KX250 silencer

    Engine Displacement: What size is it (250-265 etc.)

    and who's kit (ESR,etc) and PV or NON-PV. Stock bore

    Compression ratio: stock

    Porting type: stock

    Altitude: where you normally ride 800ft- 3000ft
    Daddy wanna twist the grip!!

  7. #7
    Junior Member porscheguy944's Avatar
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    1988 trx250r
    stock?
    I have a 1986 stock cyl on a 1988 bottem end no porting done to it at all.
    34mm kiehin carb
    K&N filter cone type?
    no lid on air box
    psi pipe dont know what type lable is missing but it is large and section welded type w/psi silencer on the end
    br8es plug
    carb says PJ03AWYG on it
    162 main jet (it had 152)ran like crap
    58 pilot (it had a 42)ran like crap
    needle is a NR1468 still in it and sudco says it should be a DGW?
    air screw 3/4 turn out
    needle in the 3rd position
    I had the stock reed cage and metal reeds
    Now it has new boysen reeds and just added a reed spacer (I hope this stuff helps)
    not the carbon fiber ones
    I live at 960 FT in MN and today it was 60F
    145 -148 psi comp wot many kicks
    can anyone help with the jetting for this thing? does not stay ideling for long
    revs right from idel
    then bog
    then mid range picks up
    then gets to lower range of high rpm well and then runs out on top end again????WTF

  8. #8
    Member roughrider's Avatar
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    1988 trx250r
    stock?
    I have a 1986 stock cyl on a 1988 bottem end no porting done to it at all.
    34mm kiehin carb
    K&N filter cone type?
    no lid on air box
    psi pipe dont know what type lable is missing but it is large and section welded type w/psi silencer on the end
    br8es plug
    carb says PJ03AWYG on it
    162 main jet (it had 152)ran like crap
    58 pilot (it had a 42)ran like crap
    needle is a NR1468 still in it and sudco says it should be a DGW?
    air screw 3/4 turn out
    needle in the 3rd position
    I had the stock reed cage and metal reeds
    Now it has new boysen reeds and just added a reed spacer (I hope this stuff helps)
    not the carbon fiber ones
    I live at 960 FT in MN and today it was 60F
    145 -148 psi comp wot many kicks
    can anyone help with the jetting for this thing? does not stay ideling for long
    revs right from idel
    then bog
    then mid range picks up
    then gets to lower range of high rpm well and then runs out on top end again????WTF
    I had an '86 cylinder on my 89'bottom end. the bore was fresh at .080 on a new bottom end also. Exaust was an FMF Fatty w/Boyeson Rad valve. Stock carb. I kept the slow jet at a #45, stock needle with clip in slot 4 from top of needle. and my main was a #158. Air filter was a K&N.Mine would idle all day. I didn't get to exactly break in the new bore before I put on an '89 jug but my setup should be a good starting point it ran fine but could have been better. I think more breaking in could have helped but I'll never know.My elevation was at sea level in s.e. WI. Give it a try.

  9. #9
    Senior Member Onski69's Avatar
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    I had an '86 cylinder on my 89'bottom end. the bore was fresh at .080 on a new bottom end also. Exaust was an FMF Fatty w/Boyeson Rad valve. Stock carb. I kept the slow jet at a #45, stock needle with clip in slot 4 from top of needle. and my main was a #158. Air filter was a K&N.Mine would idle all day. I didn't get to exactly break in the new bore before I put on an '89 jug but my setup should be a good starting point it ran fine but could have been better. I think more breaking in could have helped but I'll never know.My elevation was at sea level in s.e. WI. Give it a try.
    Mine sounds similar to yours, '89 bottom, '86 cylinder, stock everything else, reeds, pipe. Mine sits pretty well with a 42 pilot, 155 main, 4th clip groove from bottom of needle, 1 1/2 turns out on air screw. I have a bog on the bottom I'm trying to get rid of right now. Runs like a 125cc, but once the powerbank kicks in...hold on. Mine idles great. Will hold a very low idle. I'm around 700' here in Texas. Set at 70 degree temp. I think I may need to go up a bit on my pilot and in a bit on the air screw to fix my prob but it's me nit-picking more than anything. It really runs like a champ.
    1987 Honda TRX250R - #326 Toobz Audio/OPS Racing TORN Series
    stock bore/ported, 38mm PJ, UNI filter, CT Mid Pipe, Boysen RAD valve, CR head gasket 210psi,
    DG silencer, PEP shocks all around, Leager -1 swingarm, Houser +2 A-arms, anti-vibe steering stem,
    Denton steering stabalizer, Durablue rear axle +2/+4.
    1987 Honda TRX250R/1989 CR500 motor hybrid
    Toobz Audio LLC - Off-road stereo systems
    Onski Powersports Inc - Motorsports racing and repair services

  10. #10
    Senior Member pro-fab's Avatar
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    Mixture ratio and fuel: 40:1 vp110: castor 927

    Carb Type: Mikuni, Keihin (PJ, A/S, etc.) (what bore is the carb?) ESR 40.5 mm

    Main Jet size: 180

    Slow (pilot) Jet size: 50

    AirScrew (number of turns out): 1.5

    Needle (what groove is the clip in, Brand, etc): middle DEG

    Reed brand and type: Stock

    Airbox: K and N no lid no snorkle

    Pipe: FMF Gold series Fatty

    Engine Displacement: ESR 310 (1st bore 293cc)

    Compression ratio: 210 PSI

    Porting type: TRX 9 (dune port)

    Altitude: 500'-2000'

    main jet is too fat need to come down to probably closer to a 170-172 and change the needle to a DGH or CEL
    86 trx310R
    ESR Keihin 40.5 mm carb 180 main jet, DGH needle, 52 pilot
    V-Force 3 carbon fiber reeds
    ESR 310 upper mid ported by Neil
    ESR TRX5 pipe and silencer
    Pro-Fab pegs
    Tag Alius bars, fly billet kill switch, billet throttle
    Billet red kicker, mag cover, brake pedal, water pump, & temp gauge
    Works tripple rate front shocks
    14/39 gearing
    FWCarbon hood, rad shrouds, & gas tank cover
    Silver full bore plastics


 

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