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Thread: shim sizes

  1. #1
    Member raffles's Avatar
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    Posted 17 March 2013 - 09:43 AM



    Hi can anyone help please i know this is a old question on all forums relating to early tw slide type carbs.

    I have read and printed off qwerty's tuning guide but am still have problems with mid speed hesitation.

    I have tried various amounts of washers and even gone back down to nil and started again but still have a dead spot when throttle opened up quickly or if on road at 30-45mph feels like its running out of fuel until throttle opened up towards stop and it pulls like a train until it revs out so i think main jet is ok.

    I have tried a #116 main jet in and ran ok still problem with mid speed so went up to #118 main still ok marginly better not much though (happy enough with wide open throttle response) the reason for #118 is that on many forums #118 seems to be best.

    currently have #42 pilot jet in this is from a early xt 350 as standard is #40 tickover is generaly ok.(reason for bigger jet, better cold starting with out full choke'only partial reqd now)

    it would be a help if anyone had measurements of shim sizes for early type carb as i have spent alot of time in garage trying to sort and at moment am starting to lose the will to live the bike has only covered 2,000 miles from new and all the parts/jets/gaskets are all genuine yamaha items.

    I must tell you that i don't live in the usa i live in england and the fuel used is unleaded (regular) 95 octane fuel so if i can get a rough idea of shim sizes i can work from that i am probably not going to get it 100% glitch free but would like it to be smooth at mid speed.

    (no popping back on deceleration standard bike apart from carb jets)

    regards Mark model tw200h 95/96 model

  2. #2
    Senior Member r80rt's Avatar
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    Only a fool would attempt it, and God help me, I am that fool!

  3. #3
    Member raffles's Avatar
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    Thanks guy's for the info it gives me some idea of what thickness people are using in carb mods than just saying (2-3 washers !!!) thats pretty vague when you are trying to work out height of needle to jet size orrifice for fuelling.

    It seems most people are using thickness from 0.40"-0.60" i will measure what i have been using and take it from there, and resize some of the thicker washers for fine tuning (using stainless steel items at present that have been hand stamped out from a friend in machine shop

    I think we should all try and help others in what way we can, i know some questions that get posted on forums can be so pathetic that it makes your blood boil when you read them but we all have hidden strengths/weaknesses in many way's not just in mechanical/engineering walks of life.

    The stress is not good for the soul, you are a long time dead if it gets too much

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