87 TDUB missing or sputtering at high speeds
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Thread: 87 TDUB missing or sputtering at high speeds

  1. #1
    Junior Member DR_Newtron's Avatar
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    87 TDUB missing or sputtering at high speeds

    Hello,

    I just learned how to ride a motorcycle last June and bought a 1987 TW200 shortly thereafter. I got it for $750, and it did need some work. I noticed from the very beginning that at high rpms, the engine would sputter or act like it was not getting gas fast enough. Since I bought it, I have done quite a bit of work on it including, new tires, new spokes for back wheel, new brakes, valve adjustment, new handle bars, adjusted float valve in carburetor, Used Sea Foam in gas tank several times, new drive chain, and added a DG V2 exhaust. It now runs much better, but it still has problems when I get to about 55 mph. It will do 50 mph no problem, but at WOT, when it gets near 55 mph, it starts sputtering. When I slow down just a little, it does fine. It also seems to have this issue at slightly lower speeds on long rides when the engine is hot. Do you think it is a jetting issue? I believe the bike originated in Washington. I am in New Mexico at about 4,600 feet AMSL. If so, I know nothing about carburetors or how to change the jetting, so any advice would be appreciated. Thanks!

    Talon
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    Senior Member CJ7Pilot's Avatar
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    Welcome!

    It could be a jetting issue, especially since you installed a more free-flowing exhaust.

    It could also be your CDI going bad. Commonly, when the CDI starts wearing out, it will run pretty well cold, then start sputtering or cutting out when it warms up.

    Based on your description though, I'd monkey with the jetting a bit more. Someone will chime in with more specific recommendations, I'm sure.
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    Senior Member SportsterDoc's Avatar
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    If you back off at wide open throttle and it gains speed, it is too lean.

    1. What number is the main jet?

    2. How high does the needle lift at WOT? (does 1987 have CV carb with a diaphragm operated slide/needle?)

    3. How does the spark plug look?
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    Number 3 ^^
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  7. #6
    Senior Member elime's Avatar
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    Stock pilot jet is #40. Stock high speed jet is #114. Jets wear out and need to be replaced. They can look perfect even using a magnifying glass but they are not. If you only want to get 2 jets from the dealer get the #40 and #114. Probably cost about $15.

    Or go to AliExpress and buy an assortment of each. They don't have a #114 but they do have a #112 and #115. Get 3 of each. And 2 #110 and 2 #118. And maybe 2 #108 and whatever else. Ditto with the pilot jets. A 3 stock size #40 and then a few leaner and richer. Total cost will be about $20 and you will have a lifetime supply or you can share them with friends. And if it still runs poorly then it probably will be the CDI. Send it to Tom Bauer and for $60 he can fix it, or spend $250 on a new CDI which you might have to do anyway.

    https://www.aliexpress.com/item/12-m...311.0.0.IBBwxr

    https://www.aliexpress.com/item/12-p...311.0.0.IBBwxr

    Good luck.
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    Senior Member Tweaker's Avatar
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    I had the same issues as you although I have the newer carb. My bikes had DG pipes put on them and the P.O. had trouble tuning the carbs, I am at sea level and needed to go up two sizes on the main jet. Also I used washers as spacers under the spacer on the needle to raise it. This improved my midrange acceleration. If your bike starts easy then stay with the stock pilot jet. I put bigger pilot jets in and now my bikes start with very little choke or no choke. Luvnot’s recent carb tuning thread has some good references mentioned in it for tuning. There is a YouTube video on how to add spacers to the needle on a TW carb.

    Here it is.
    Last edited by Tweaker; 01-18-2018 at 09:58 AM.
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    Twin 2014 TW200's made side by side on the assembly line, Moose rear racks, Protaper ATV high bars, DG oval pipes, kick starters, rejetted carbs, 130 main jets, 2 -3 -.020 shims on the needles and @ 2 1/2 turns on the pilot screw, #34 pilot jets, Acerbis hand guards, Shinko 241 front tires, modified Krator foot pegs, 14-55t sprockets, Ricochet skid plates and 90 degree fuel filters.

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    Member Blake's Avatar
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    Another quick check is to turn the choke on slowly at high speed during the stutter. If the stutter decreases you are to lean. If it gets worse usually too rich.
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    Senior Member Tweaker's Avatar
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    Twin 2014 TW200's made side by side on the assembly line, Moose rear racks, Protaper ATV high bars, DG oval pipes, kick starters, rejetted carbs, 130 main jets, 2 -3 -.020 shims on the needles and @ 2 1/2 turns on the pilot screw, #34 pilot jets, Acerbis hand guards, Shinko 241 front tires, modified Krator foot pegs, 14-55t sprockets, Ricochet skid plates and 90 degree fuel filters.

  11. #10
    Junior Member DR_Newtron's Avatar
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    Quote Originally Posted by SportsterDoc View Post
    If you back off at wide open throttle and it gains speed, it is too lean.

    1. What number is the main jet?

    2. How high does the needle lift at WOT? (does 1987 have CV carb with a diaphragm operated slide/needle?)

    3. How does the spark plug look?
    It does not gain speed when I back off wide open throttle. It slows slightly and stops cutting out or sputtering. The tip of the spark plug is a dull dark brown color. I do not know if you can see it really well in the attached picture or not. It may be running slightly lean. It was running rich before, and I lowered the float a little in the carburetor. It did not like it when I installed a high air flow K&N air filter. I cannot answer the first two questions. I assume the the main jet is stock, but I am not sure. If you could point me to a reference to help me answer those questions, I would appreciate it. Thanks for your help.
    Attached Images Attached Images
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