1987 carburetor fuel/air screw
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Thread: 1987 carburetor fuel/air screw

  1. #1
    Senior Member dizzle2's Avatar
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    ok, so the previous owner of my 1987 tw200 removed the little brass plug on the carb and the fuel/air mixture screw is exposed. so, i have a feeling that he also adjusted it. the bike seems to sometimes hesitate when giving it throttle and have little "hiccups" when cruising/ have little engine power surges(thats the best way i can explain it.haha). ive been through everything i could think of and this is the last thing i can think of to cause this problem. i was wondering if anyone can give me some insight on adjusting the screw for maximum performance as well as the factory reset...? thanks!

  2. #2
    Senior Member RodneyReed's Avatar
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    Start out at 1/4 turn out from fully seated. Then turn it out 1/4 turn at a time. If it gets better, keep going. If it gets worse, go back 1/4 turn and you've got it. See post below for more info:



    https://tw200forum.com/index.php?/topic/647-carb-tuning/

  3. #3
    Senior Member dizzle2's Avatar
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    hey, i came across this and was wondering if this is the newest(smoothes) tw carb? http://www.cheapcycleparts.com/model...emblies/212132 and also if it would be worth switching to in comparison to the old style 1987 model carbs? thanks

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  5. #4
    Senior Member RodneyReed's Avatar
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    Quote Originally Posted by dizzle2 View Post
    hey, i came across this and was wondering if this is the newest(smoothes) tw carb? http://www.cheapcycleparts.com/model...emblies/212132 and also if it would be worth switching to in comparison to the old style 1987 model carbs? thanks


    IMHO, it's not worth switching, except under extenuating circumstances, like your carb is ruined and you happen to have the newer style carb on hand. Even then, it may be more trouble than it's worth.

  6. #5
    Senior Member dizzle2's Avatar
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    the stupid fuel mixture screw is impossible to get to on this thing unless i take off the throttle cables and twist it horizontal. then i have to put everything back on and test it. and then i have to keep repeating till i get the setting just right!

  7. #6
    Senior Member RodneyReed's Avatar
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    Look in the link I sent. Qwerty was able to fabricate a tool to adjust without moving the carb.

  8. #7
    Banned qwerty's Avatar
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    Power screwdriver bit and duct tape. Works like a charm.



    desertdenizen likes this.

  9. #8
    Senior Member dizzle2's Avatar
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    now the damn thing is still doing it. sounds like its dropping a cylinder. if it is a misfire issue, is the ignition coil a good place to start?

  10. #9
    Senior Member dizzle2's Avatar
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    ignition coil is fine. i tuned the fuel mixture screw to the point that it runs good at low rpms but as soon as it hits mid-high rpms it surges, and backfires as i let off the throttle. it has a new spark plug and when i took it out the blug base was black but the tip had a little white on it. almost as if it runs lean and fat...wow, is this possible. im starting to think i should rejet. what size jets should i get/what kind of washers to shim the needle? i still have the stock airbox....

  11. #10
    Senior Member demarko69's Avatar
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    I have had a couple 87 and they seem to like 116-118 yamaha jets upto 4k elevation, haven not shimmed them

    Pilot at 2.5 and 3 turns is good.

    Clean filter and lightly oil it



    Make sure it is getting fuel, make darn sure the petcock flows. Screens may be clogged. Use clear fuel line, also the the float could be a problem, the needle and seat could be clogged and or blocked with debris. There is a small fine screen on the top of the needle and seat and it does not take much to clog it. Even if you cleaned the carb you shouldchange the needle and seat as a pair. Make sure your vent tubes are clear and the gas cap is venting (non-CA), there is a small bb check valve that gets stuck closed.

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