Paper Clip in my '93 Carb..??
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Thread: Paper Clip in my '93 Carb..??

  1. #1
    Member Goofy Footer's Avatar
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    When I purchased my '93 TW a month ago, the previous owner mentioned he recently did some carb work. He was having some issues getting the carb dialed and was drilled a small side hole in the airbox so he could shoot starter fluid into the air intake. He mentioned something about a paper clip and I told him I wasn't too concerned, I've rebuilt carbs before...



    After replacing the old gas that was in the tank and putting running some 91 octane gas/seafoam mix through the carb, it seemed to run better. I still had a flat spot down low and a hanging idle. Coming off throttle through a turn for instance, the idle would stay high and I'd have to throttle on then quickly dethrottle to break the hang.



    Some pictures of the carb when I opened it up today:



    Notice something unusual?





    Yup, a Paper Clip in my main jet!





    Here are the jets, they checked out clean:







    I figured I had to throw some pictures of the bike into this thread!





    The water is the Pacific Ocean. The left half of the distant land is Mexico, the other half USA











    Carb Stats:

    Idle Jet - 40

    Main Jet - 114 (was plugged by paper clip)

    Fuel Screw - 1.25 turns out



    The baseline for the fuel screw on most four strokes is 2-2.5 turns out. I have a 116 and 118 jet and some washers from Ayers Garage. I ride in Southern California 0-4,000ft. I'm thinking Idle Jet 40, Main Jet 116, Fuel Screw 2.5 turns and 1 washer for the needle.



    Any thoughts on my mystery hanging idle? Thank you for reading and I appreciate your thoughts/tips!
    '93 TW200 :: '00 DRZ400E Plated :: '06 WR250F Plated

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  2. #2
    Member Jvanvuren's Avatar
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    I've seen that done before, usually after somebody drills the jet way too much. Just because it says 114 on the side doesn't mean it hasn't been drilled larger. Compare it to your other main jets. If you want to get fancy, you can do the calculations and figure out roughly how much area there was for fuel to flow through, if you can accurately measure the hole and the paper clip.
    '87 Street Tracker / Scrambler - hollow mod, underseat exhaust, vintage tank, custom seat

    '95 Offroader - D606 front, Bighorn rear, Cyclerack, 14/63 sprockets

  3. #3
    Member Goofy Footer's Avatar
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    Quote Originally Posted by Jvanvuren View Post
    I've seen that done before, usually after somebody drills the jet way too much. Just because it says 114 on the side doesn't mean it hasn't been drilled larger. Compare it to your other main jets. If you want to get fancy, you can do the calculations and figure out roughly how much area there was for fuel to flow through, if you can accurately measure the hole and the paper clip.


    Woa thanks for the input. I would have never guessed its a common thing ha. I think the main jets were $5 or something at my local dealership.



    I'll be interested to see if my "new setup" will cure the idle hang. I don't think there was any air leak.

    idle jet - 40

    main jet - 116

    needle - 1 shim

    fuel screw - 2.5 turns out





    On bikes like the DRZ and DR650 they speak of a 3x3 airbox mod where you cut the top of the airbox to improve flow into the intake. I haven't found a definitive answer for an airbox mod (besides the hollow frame mod) on the TW. Is it common to cut off the snorkel on TWs?



    Thanks!
    '93 TW200 :: '00 DRZ400E Plated :: '06 WR250F Plated

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  5. #4
    Senior Member lizrdbrth's Avatar
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    There's no magic bullet when it comes to the idle mixture screw, no matter what you've heard.



    I recomend you remove the shim and put a legit, known 114 or (at most) 116 in there while sorting this out, but that's just me. That takes main jet leakage out of the equation. But the proper procedure for adjusting idle mixture is as follows:



    Warm your bike up. Adjust the idle for a couple hundred rpm or so above what you normally run.



    First, frontseat (close) the idle mixture screw 1/2 turn at a time and make sure the engine COMPLETELY dies when it's fully closed or just slightly beforehand. If it doesn't, your idle jet is too big. Maybe someone drilled it er sumpin'. Conversely, if your engine dies somewhere nearer to 1 turn out than it does to zero turns, your idle jet is either too small or is partially clogged.



    Now backseat (open) the screw to 2 turns. Start the bike and again begin to frontseat (close) the mixture screw with engine at high idle 1/2 turn at a time. Allow it to settle down each 1/2 turn. Once the idle begins to slobber or become uneven, count the turns out at which it occurs.



    Then do the same procedure in reverse. Open the screw 1/2 turn at a time, allow it to settle, then when the idle begins to slobber again, count the turns out at which it occurs.



    Now split the difference. If for exmple the idle craps at 1 turn closed then again at 2 turns open, your starting point is very close to the vicinity of 1 1/2 turns.



    That's a far cry from the recomended 2 1/2-to-3 turns, no? Whatever that number turns out to be, yer about done. Bring the idle speed back down to normal RPM, makes sure you still have a smooth, crisp idle. Only then are you ready to procede with the main jet and lifting the needle.



    Any pat formula for jets and shims are crap, as well. Main jet first til it's right, THEN lifting the needle. When you cease to realize gains or are running rich it's time to stop or even reverse the change. It's really difficult to avoid placebo effect, so take the time to read your plug.



    Same thing with airbox and exhaust mods. Perfect one thing before moving on to the next so you have a baseline and things don't become a mishmash of issues on top of previously unresolved issues. It's pretty hard to UNCUT a hole in your airbox. Removing the snorkel is relatively harmless but even that should only be done AFTER you've got the jetting right with it in place. Removing the snorkel introduces intake noise which can also contribute to placebo effect. That sudden audible rush of air can give the sensation of more power just as can the racket of an aftermarket exhaust. Make sure you actually gained something from it before moving on.



    If you want to you can refine things even further by using 1/4 turn increments during the idle jet adjustment but seldom is it ever gunna be anywhere near a pat number for every bike.



    I suggest you not mess with airbox mods until you get your idle issue and main jet selection squared away. Opening up the airbox will neither cure nor improve your idle issues.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  6. #5
    Member Goofy Footer's Avatar
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    Quote Originally Posted by lizrdbrth View Post
    There's no magic bullet when it comes to the idle mixture screw, no matter what you've heard.



    I recomend you remove the shim and put a legit, known 114 or (at most) 116 in there while sorting this out, but that's just me. That takes main jet leakage out of the equation. But the proper procedure for adjusting idle mixture is as follows:



    Warm your bike up. Adjust the idle for a couple hundred rpm or so above what you normally run.



    First, frontseat (close) the idle mixture screw 1/2 turn at a time and make sure the engine COMPLETELY dies when it's fully closed or just slightly beforehand. If it doesn't, your idle jet is too big. Maybe someone drilled it er sumpin'. Conversely, if your engine dies somewhere nearer to 1 turn out than it does to zero turns, your idle jet is either too small or is partially clogged.



    Now backseat (open) the screw to 2 turns. Start the bike and again begin to frontseat (close) the mixture screw with engine at high idle 1/2 turn at a time. Allow it to settle down each 1/2 turn. Once the idle begins to slobber or become uneven, count the turns out at which it occurs.



    Then do the same procedure in reverse. Open the screw 1/2 turn at a time, allow it to settle, then when the idle begins to slobber again, count the turns out at which it occurs.



    Now split the difference. If for exmple the idle craps at 1 turn closed then again at 2 turns open, your starting point is very close to the vicinity of 1 1/2 turns.



    That's a far cry from the recomended 2 1/2-to-3 turns, no? Whatever that number turns out to be, yer about done. Bring the idle speed back down to normal RPM, makes sure you still have a smooth, crisp idle. Only then are you ready to procede with the main jet and lifting the needle.



    Any pat formula for jets and shims are crap, as well. Main jet first til it's right, THEN lifting the needle. When you cease to realize gains or are running rich it's time to stop or even reverse the change. It's really difficult to avoid placebo effect, so take the time to read your plug.



    Same thing with airbox and exhaust mods. Perfect one thing before moving on to the next so you have a baseline and things don't become a mishmash of issues on top of previously unresolved issues. It's pretty hard to UNCUT a hole in your airbox. Removing the snorkel is relatively harmless but even that should only be done AFTER you've got the jetting right with it in place. Removing the snorkel introduces intake noise which can also contribute to placebo effect. That sudden audible rush of air can give the sensation of more power just as can the racket of an aftermarket exhaust. Make sure you actually gained something from it before moving on.



    If you want to you can refine things even further by using 1/4 turn increments during the idle jet adjustment but seldom is it ever gunna be anywhere near a pat number for every bike.



    I suggest you not mess with airbox mods until you get your idle issue and main jet selection squared away. Opening up the airbox will neither cure nor improve your idle issues.


    I set the fuel screw at 2.25 and played around with it. I felt at 2.25-2.5 was fine. I put the 116 main in and at full throttle the bike started cutting, eerrr, eerr, eerr, eerr and wasn't running clean. I should have read that as too rich but I was thinking too lean.



    I got greedy and went for a home run, installing a 118 and 2 needle shims. Ive read that multiple guys run that set up with positive results. 0 throttle to 1/4 throttle felt great but everything else was horrible. It wouldn't rev out and was jumpy.



    Back to the basics... bone stock settings (without the paper clip that is). Any tips on how to adjust the fuel screw while the bike is running?



    I appreciate the input
    Fred likes this.
    '93 TW200 :: '00 DRZ400E Plated :: '06 WR250F Plated

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  7. #6
    Senior Member lizrdbrth's Avatar
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    Some guys use a bit from a 4-way screwdriver, shorten the handle on a stubby screwdriver, etc.



    Your pilot circuit is open 24/7, so ta speak, so it's a component of your total fuel volume at w.o.t.



    That's why it's so important. If your pilot circuit is lean or rich the cumulative effect of whatever main jet you install will be leaner or richer accordingly. Hope that makes sense.



    Fred likes this.
    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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    Senior Member Gerry's Avatar
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    Boy, I can't imagine that the O.D. of a paper clip small enough to represent the orifice diameter of any small displacement (carburetor jet) engine. Perhaps I have found a new 'tool'. Gerry



    Per Lizrdbrth above:



    Fred likes this.
    Take care my Friend.........

  9. #8
    Member Goofy Footer's Avatar
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    Quote Originally Posted by lizrdbrth View Post
    Some guys use a bit from a 4-way screwdriver, shorten the handle on a stubby screwdriver, etc.



    Your pilot circuit is open 24/7, so ta speak, so it's a component of your total fuel volume at w.o.t.



    That's why it's so important. If your pilot circuit is lean or rich the cumulative effect of whatever main jet you install will be leaner or richer accordingly. Hope that makes sense.


    That makes sense. In an effort to do things incrementally, I took out the 2 shims and rode the 118 around. It was still rich but ran better without the shims than with the shims. I'm going to work my way down (leaner) slowly. On my ride around the neighborhood, I saw a TW parked. I'm going to leave a note for the owner to check out tw200forum.com



    Lizrdbrth, out of curiosity, how many turns is your fuel screw set at?
    '93 TW200 :: '00 DRZ400E Plated :: '06 WR250F Plated

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  10. #9
    Senior Member jbfla's Avatar
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    Quote Originally Posted by lizrdbrth View Post
    ...Any pat formula for jets and shims are crap, ...
    Liz, you have such away with words....



    Jb
    2018 Triumph Street Twin..............2016 CB500F
    2014 XT250 ..................................2008 H-D Softail Deluxe
    2008 SV 650..................................2007 DR 650..

  11. #10
    Senior Member lizrdbrth's Avatar
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    Quote Originally Posted by jbfla View Post
    Liz, you have such away with words....



    Jb


    Been holding that in for years



    Fred and jbfla like this.
    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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