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Discussion Starter #1
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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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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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.
 

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Discussion Starter #5 (Edited)
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...
 

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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.)
 

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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.
 

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Discussion Starter #10
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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My last TW started fine when the outside ambient temps were higher. If it was just a little cool it would not start. What would occur is it would start then die and never restart. At about 1 year old I took the carb apart and found a piece of aluminum from the bowl casting was blocking fuel that were to the "choke" enriching valve. I cleaned that out and never had another starting issue again. When I purchased my new on 2 weeks ago. I was talking to the service manager and he new about this as having been an issue.
 

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Hard to start but running better once warmed up can mean a valve adjustment is needed. Intake valve not allowing enough fuel into the can until it heats up a bit.
 

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Discussion Starter #16
Hard to start but running better once warmed up can mean a valve adjustment is needed. Intake valve not allowing enough fuel into the can until it heats up a bit.
The valves are well adjusted, Adjusted them last summer and did not even do 100 Km with the bike
 

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Here is how it can be !! Very happy after some tuneup work last week. Neither bike ran for crap or at all before cleaning and adjustment. I am at 800' asl

2016 started hard and other issues, I found 2 shims in the carb under the needle spacer, removed those and adjusted the pilot screw to 2.25 turns out.

2003 with a DG pipe is back to stock jetting and the pilot screw is at 3.25. turns outand is ok but clearly would be better with a 34 pilot in place of the stock 31 and the screw could likely be re-tuned back down into the 1-2 turns range for further improvement.

 

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Glad for the major improvements!

When the best idle is with mixture more than about 2 3/4 turns, a richer pilot jet is indicated (unless there is a vacuum leak).

BTW, for all seeing the video, the life of the starter solenoid will improve if the button is held (up to ~ 10 seconds) until started.
It is the interruption of DC amps that burns the solenoid contacts.
Not intending to be critical, just a suggestion to increase longevity.

Also, the TW200 (and XT250) use an overrunning starter clutch, so the starter will not drag with the motor fires.
 
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