TW hard to start when motor cold
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Thread: TW hard to start when motor cold

  1. #1
    Senior Member Tw200quebec's Avatar
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    TW hard to start when motor cold

    Hello fellow TW owners, My sister's Tw is very hard to start when the engine is cold, once it's started and engine is warm starts great and runs great. I rebuilt and installed a after market carburetor kit because is was leaking gas from the float needle. The OEM part cost as much as a complete after market carburetor rebuilt kit. So I got Moose brand rebuilt kit and changed all the needles gaskets... Now the carb is not leaking fuel anymore but it's hard to start when cold, so I believe it has something to do with the carb... I adjusted the pilot screw tried pretty much every position with no positive results. Would there be a problem with the after market pilot screw? I believe the part is available OEM. Would changing the pilot screw help any...? The bike runs great when the engine is hot and to my knowledge it's the pilot screw that is important on cold start up. Bike runs great from close throttle to full when hot, so in theory the slow and main jets are good... Thanks for your help

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    Senior Member Heli-Mech's Avatar
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    What's the spark plug look like? After cold cranking it a bit pull the plug and see if it's wet .... also check the gap and make sure it's within spec.

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    Senior Member elime's Avatar
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    What size pilot jet was in it before the rebuild and what size is in it now? Sometimes hard cold starting can be solved with next size larger pilot jet.
    Long live the internal combustion engine!

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  5. #4
    Senior Member Tw200quebec's Avatar
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    Quote Originally Posted by Heli-Mech View Post
    What's the spark plug look like? After cold cranking it a bit pull the plug and see if it's wet .... also check the gap and make sure it's within spec.
    The spark plug is brand new...

  6. #5
    Senior Member Tw200quebec's Avatar
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    Quote Originally Posted by elime View Post
    What size pilot jet was in it before the rebuild and what size is in it now? Sometimes hard cold starting can be solved with next size larger pilot jet.
    Same size as OEM 126 main and 31 pilot... Thanks you made me think of something, going to reinstall the old OEM pilot and main jets and see... I believe I kept them...
    Last edited by Tw200quebec; 01-30-2018 at 06:41 AM.

  7. #6
    Senior Member elime's Avatar
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    Quote Originally Posted by Tw200quebec View Post
    Same size as OEM 136 main and 31 pilot...
    You have the new carb. and my experience is with the older type, however I have read that using a #34 pilot often cures hard starting problems. And shouldn't the main jet be #126?
    Tweaker likes this.
    Long live the internal combustion engine!

  8. #7
    Senior Member Tw200quebec's Avatar
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    Quote Originally Posted by elime View Post
    You have the new carb. and my experience is with the older type, however I have read that using a #34 pilot often cures hard starting problems. And shouldn't the main jet be #126?
    Yes sorry I meant 126

  9. #8
    Senior Member SportsterDoc's Avatar
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    Some likely possibilities, if you have good spark and valves are fully closing:
    1. Mixture screw closed more than about 2 1/2 turns
    2. Pilot jet is obstructed
    3. Pilot jet is too small
    4. Vacuum leak (was carb lubed [water, diluted liquid soap, spit] when it was re-inserted into the rubber intake?)
    5. Enrichener on CV carb not working (o-ring leaking, etc.)
    Last edited by SportsterDoc; 02-03-2018 at 06:15 PM.
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  10. #9
    Senior Member Dubster's Avatar
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    When I first got my 03 TW I shimmed the needle and upped the main jet from stock to a 130 and adjusted the pilot screw. I never had any problems starting it during the cold winter months. Before a planned trip in excess of 4000 kilometers I reinstalled the stock jet and removed the shims to get the best fuel mileage I could. I left the pilot screw where it was. Since then the bike simply would not start during the cold months unless I warmed it up or removed the plug and primed with a squirt of gas and like your sisters TW it ran great once I got it running . I finally got tired of this and replaced the shims and 130 main jet a couple weeks ago. BAM the bike starts at the touch of the starter without the choke. I'm not sure if you would get the same results but it might be worth a try. FYI I used two .50mm shims/washers on the needle.
    Last edited by Dubster; 02-06-2018 at 07:35 PM.
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  11. #10
    Senior Member Tw200quebec's Avatar
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    Today, I just took the carburetor off and reinstalled the old OEM main and pilot jet, lucky I kept them from when I used the Moose rebuilt kit. The bike which was stored all winter started pretty well for a bike that has not started for the past few months. Bottom line when rebuilding the carb, use OEM Yamaha parts... especially the jets!

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