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cold start 2001 sportster 1200

Discussion in 'Motorcycle Tech Talk' started by todd, Nov 17, 2015.

  1. todd

    todd Member

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    Did the vacuum test, with no results in the change of idle. Carb has been off with new accelerator diaphragm and cleaned . Did not look bad inside. If you start the bike when its cold its either a little carb cleaner shot or your hand. It back fires until it is warm then it runs and idles like it is suppose to. But if it sits there and cools down it is back to the above mentioned tactics. New coil and new plugs new filter in the tank. For some reason it acts like no fuel when it is cold.
  2. hotroadking

    hotroadking Super Moderator Staff Member

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    The choke cable might not be working properly,
    does it stay out when you open the choke or pull back in.

    I'd remove the cable, clean the area good, might be some
    schmutz in there, re-seat the cable, and make sure it's properly
    installed, the backing screw is an adjustement (that goes behind the
    mounting tab on the tank)

    The choke should take care of all of that for you.
  3. todd

    todd Member

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    I did completely remove the cable when I had the carburetor off. There was some black schmutz and I cleaned it. I adjusted the tension screw on the mount and it is staying out. It tries to fire when I first crank it but then the battle is on. Carb cleaner has become my friend. Maybe the entire cable needs to be replaced, Your thoughts
  4. hotroadking

    hotroadking Super Moderator Staff Member

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    Fire, fuel, compression.

    Since it runs once it's warm it leads me to believe it's
    not getting enough fuel, starting fluid shouldn't of course
    be needed.

    When it was cleaned did you clean the whole carb?
    Reset float? Make sure float works?
    Make sure jets are clear?

    Still sounds like the choke, did you use carb cleaner to clean out the passages where the choke cable attaches?

    Choke Cables are not expensive but don't toss bucks at it
  5. todd

    todd Member

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    I did clean entire carb, jets out, mixture screw out, float out, choke out and all passages cleaned with carb cleaner and air. I did not reset float (measure) but I guess I will re pull and set to specs. Definitely starving for fuel on cold start, I did loosing the drain screw after it setup to make sure it had fuel in the bowl and it did.
  6. Marc1340

    Marc1340 Active Member

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    I agree with HRK check the float level, make sure that when you crank the throttle you are getting a good squirt into the carb before she starts., also make sure that the bowl is not leaking after she is parked draining the bowl. I had a long story a year back and everyone helped out here to solve it...it was the float level. Let us know how you make out.
  7. hotroadking

    hotroadking Super Moderator Staff Member

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    if the float is off and not completely filling then its possible when the
    choke is engaged that it can't pull up enough fuel to start it cold...
    Marc1340 likes this.
  8. baggerpaul

    baggerpaul Well-Known Member

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    Take the hose off the carb .hook a mighty vac.to the vacuum line on the tank put about 10 inches of vacuum to it and check for fuel flow .
  9. baggerpaul

    baggerpaul Well-Known Member

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    Cranking vacuum and idle vacuum are very different
    Marc1340 likes this.
  10. Lucifer

    Lucifer Well-Known Member

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    BP is this test to find out if the vacuum operated petcock is functioning properly??
    todd mentioned to me that when he does have it running and pulls the choke out,the idle changes,which makes me think his choke is working,so the petcock not opening enough while cranking seems likely
  11. baggerpaul

    baggerpaul Well-Known Member

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    Yes sir

    Sent from my SGH-M919 using Tapatalk
  12. baggerpaul

    baggerpaul Well-Known Member

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    Vacuum should hold also

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  13. hotroadking

    hotroadking Super Moderator Staff Member

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    Might just inspect vac line first for cracks.

    If it has an aftermarket petcock there should be a rubber cap on the vac port on the carb if it's cracked or missing same issue


    Sent from my iPhone using Tapatalk
    Marc1340 likes this.
  14. todd

    todd Member

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    Alright Guys and update. Got the new mixture screw set and a manually operated petcock installed. It fire right up for about 5-7 seconds running great and then killed. I adjusted mixture to about 3/4 turn out but still cannot get it to stay running after starting it cold.

    I gave it the hand choke and once again it fired up without any back firing at all this time. Rode it down the street and it runs like a champ and idles just fine. I let sit over nite and notice a little puddle of gas that came out of over flow. Im thinking float may need adjusting. Thats all that is left besides seeing what size pilot jet is in it. Will reply
  15. todd

    todd Member

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    also am not hearing or seeing a squirt of gas before starting, should I hear that on a CV carb before starting. Also has a new pump diaphragm installed
  16. Marc1340

    Marc1340 Active Member

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    The needle and float are very cheap to replace, sounds like it is over running, maybe the rubber on the needle is dry cracked and leaking by, look for the 4 sided needle as I have heard the 3 sided sometimes hangs up. When checking the jets make sure they are really clean, and yes you should see a squirt of gas when you crank the throttle in the front of the carb from the small post that sticks up in front, you can check the pump is working when you have it off and fill with fuel and pump it, be careful it will spray all over the place if it is working right. I set mine a while ago using a block of wood cut to 15 degrees and float should be perpendicular to the base when sitting on the wood block.
  17. Lucifer

    Lucifer Well-Known Member

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    OK, Is this what you did?? You pulled the choke out and it stayed out,then you fired up the bike and it ran good for a short time(5-7secs). Was the choke still pulled out when it quit,or did you push it back in and it quit?? The choke has to stay out for a minute or so and then you push it in half way for another minute or so,then after the engine is warmed up push all the way back in.The choke should stay pulled out until you manually push it back in.
    Idle mixture screw should be set between 1 1/2 -3 1/2 turns out from gently seated,less than 1.5 turns out would show pilot jet is too big,or you have the idle mixture too lean. What pilot jet is in it??
    Between 2-3 turns out should be the sweet spot with the proper pilot jet.
    With a manual/gravity fed petcock,you should turn fuel off when engine is off. The float could be sticking a bit or inlet valve worn,check the rubber tip on the inlet valve for a little ring type mark(worn). Sometimes a little tap on the float bowl with a screwdriver handle will unstick the float. It might need to be adjusted.
    Marc1340 likes this.
  18. Lucifer

    Lucifer Well-Known Member

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    The accelerator pump nozzle should stream fuel into the carb when you twist the throttle only.
    Marc1340 likes this.
  19. hotroadking

    hotroadking Super Moderator Staff Member

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    the stream should hit the back center of the manifold,
    you may be able to rotate it with a set of needle nose pliers
    if needed.

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