Carb stories..and How to Tell your too lean
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Thread: Carb stories..and How to Tell your too lean

  1. #1
    Member Hotrodjohn's Avatar
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    Jul 2011
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    Ive been working on three TW's in the last few months. All of them I had to go through the carb. I have found that these carbs are Very sensitive to the airbox and filter.. If you have a disappearing or dried out air filter or any air leak behind the carb, it will run lean. Obviously a carb boot leak will cause a problem as well. One of the TW's i got had no air filter because it had disintegrated over time. It popped and surged and was lean. A newly oiled air cleaner fixed that problem. My 89 TW would run perfect unless you held it at 60 plus for a minute or two and it would die as if starving for fuel. That turned out to be a clogged inlet screen on the float valve. Seems both the petcock screens and the float inlet screen will gum up over time. It would let enough fuel in if the demand wasnt too much, but wide open for any length and it was too restricted to keep the bowl full. All three of mine have the stock 116 main and no washers and run fine. None of them surge or run lean on the main. They will all hit 70 plus on the speed and have a tan colored plug. But if you take out the restriction of the air filter and box and they will lean out with a an accompanying hot exhaust and white plug. Anyway, Ive determined that if you have it right, a TW will idle low and smooth and you can touch the front exhaust guard for at least 8 seconds with your finger. If you touch the guard on your exhaust and you cant hold your finger on it for a few seconds, you are probably lean. I could touch mine at idle and after a sustained top speed run for at least eight seconds. Another thing I noticed is that if you have the slide up too much on the idle screw, it causes a surge at idle because apparently there isnt enough vacuum to pull the low/ pilot thru, it is easy to turn up the idle screw, which raises the slide, too high without the idle going up. I would turn it down until it almost died and then back up a bit. This results, assuming your low jet and pilot circuit are clean and your air filter is in, in a very smooth idle without any miss or hiccup.
    87 (2) TW200 89 (2) TW200

    91 Honda XR250L

    97 Honda Valkyrie

    01 Kawasaki KDX200

    78 Suzuiki GS1000

    1970 (2) CT70H

    1974 Suzuki GT185

    1981 Honda C70 Passport

  2. #2
    Senior Member peruano's Avatar
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    Hotrodjohn, Thanks for the analytical explanation and guidance. Alas solutions that don't involve custom jets, 72 iterations of washers, and custom air intakes will not be widely accepted unless you can figure out how else we should spend that disposable income. Your post does make me want to pay more attention to my airfilter hygiene. Thanks again. Tom
    Tom - TW200 2002, Kawasaki VN 500 2006

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  3. #3
    Junior Member jerz006's Avatar
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    okay I have had a lot of carb problems. This is my first bike and im a newbie at 24. I purchased my bike when i was 23 drove it with a little sputter problem between second and third. i drove my bike in fields by train tracks and on back streets till i could afford my license before i got my license i got a flat and my bike set for about two months i tried to clean the carb my self from the lazy tk cleaning tutorial to no avial i dedided to let a pro do it because after reassembly and the add on of my pod filter it would not stay on once cranked and would pop and make sucking sounds one guy told me it was just that the jets a really dirty and need to be cleaned. the guy told me just bring him the carb and he would restore every thing to the original settings i decided against the pod filter because it rains alot here in fl and sometimes flood a little and i still wanted to be able to ride threw streams and such after the guy cleaned it he said i was missing some parts the baffle plate and he said that my fuel wouldnt stabilize with out it so i decided to get the parts and another opinion bcuz my bike never had problems before. i had another guy look at it he said my air fuel mixture was off and he would fix it . it seemed fine with minor adjustments needed to get it completely back to how it was. Since i did get it running again my self but its kinda off a little not sounding the same as it did before. I thought he could fix it being that he is a "pro and costumize and race bikes its staying on for longer before it would cut off if you dont give it gas its not idling right but i paid him for his time and as soon as he leave the bike shuts off so now im back where i started when i opened the airbox... guess what? no filter it was just a rag so my filter, baffle plate, and float bowl gaskets on the way so thats good. but when we took of the spark plug it was all black soot around it he recomended getting a new plug and that should help all my problems i just got my license and really wanna ride. So once i get my parts ill keep you all updated and if any one can help me it will be greatly appreciated. if any one is in fl with in travel distance i can come to you or if you know a good mechanic or any thing that will help for that matter. god bless every one im not good with grammar so if this hard to understand i apologize ahead of time

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  5. #4
    Member Hotrodjohn's Avatar
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    Ive worked on alot of bikes over last 30 years and these seem really sensitive to any airflow change. I guess your talking about the little baffle on the bottom of the main jet? One of mine was missing and it runs fine without but I have ordered a new one. I live in Texas and do believe these TWs will run fine with the 114 main and no washers if everything is clean and the airbox is sealed and an oiled factory filter is in. Thats been my experience anyway. The only adjustable mixture is the pilot and 2.5 to 3 turns seems to always work. the 40 size low jet I dont think ever needs to be bigger. Raising the needle and putting in a bigger main jet is simply letting in more fuel at mid and high range thus giving a richer mixture. Putting a pod on is simply letting in a lot more air and making you lean, just like no air filter on the stock box. I say keep it stock, Yamaha engineers are pretty good at what they do. These run great when they are right. YOu can go wide open and let off and is should quickly go back down to idle and not miss a bit. When its right it will be smooth transitioning from the pilot to the needle to the main, period. If it doesnt, something isnt right.
    cowboyjeff likes this.
    87 (2) TW200 89 (2) TW200

    91 Honda XR250L

    97 Honda Valkyrie

    01 Kawasaki KDX200

    78 Suzuiki GS1000

    1970 (2) CT70H

    1974 Suzuki GT185

    1981 Honda C70 Passport

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