Carbed Twin Cam hard to start warm

Discussion in 'Engine, Fuel and Exhaust' started by Broiler, Oct 2, 2010.

  1. Broiler

    Broiler New Member

    Thanks in advance for any help. This is my first post.

    So this is my 2nd Harley. 01 springer. Dont know if I like working on it or riding it more. Engine starts right up when its cold, one blip and its running. But, when warm, takes a good 4-5 seconds of cranking to get it going. Runs fine thereafter but can be a bear to start when its hot (engine). Outside temperature seems to make no difference. Stock carb, SS filter, strait pipes. Thats about the extent of the mods to the engine.

    Any ideas?

    Is it possible it could be vapor lock?

    Thanks for any info
  2. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    could be that you are a little on the lean side during cold starts you will use the enricher (choke) which will give you a richer mixture
    during warm/hot starts you wont be using the choke control
    to give a wee bit more fuel during a hot start snap the throttle open once or twice prior to starting the will cause the accelerator pump to squirt some neat fuel into the throat of the carb
    or try to pull out the choke control just a wee bit
    if either of those methods give better starting then id be looking at the carb jetting after that

  3. Broiler

    Broiler New Member

    Thanks, I guess I should have included that It does this with or without the choke. In fact, I dont need the choke when its cold, and it seems to start sooner with it when its hot. ?? Throttle crack makes no difference.
  4. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    I would start with the basics. Make sure the battery connections are good by removing both ends of both cables (neg off first, on last), wire brushing them clean and resecuring.

    Then do a simple charging system test:

    Testing The Charging System - Harley Davidson Community

    Once you have ruled out a weak battery or charging system, it is on to the fuel system. If you have a vacuum operated petcock, replace it with a high flow manually operated one like the Powerflo from Pingel. Clean out the tank while it is open:

    Power-Flo™ Fuel Valves

    Then go through the fuel system making sure everything is good. Replace the fuel line from the tank to the carb. Drop the float bowl and clean out the crud if any. Chase all the ports with carb spray. Open up, clean and inspect the accelerator pump diaphram. Remove the idle-air misture needle valve and chase the port with carb spray. Check what size jets are in there so you know.

    Reassemble every thing, adjust the idle-air mixture at around 1200rpm, and see how she does.

    Let us know.

  5. maine-e-axe

    maine-e-axe Junior Member

    If it starts without the choke when it's cold then I would say it's running on the rich side. Are the pipes black w/soot on the inside? If so try "holding" the throttle wide open on a hot start to give it more air to see if fires faster.
  6. Hoople

    Hoople Account Removed

    A few things enter my mind. Plugs, wires, and crank sensor. A few years back on a Metric bike, I saw a crank-sensor having low output just when it was hot. Remember those sensors are RPM dependent for output. Therefore once the engine is running, output will be High. But during slow cranking speeds the signal can be marginal.

    1) Take your meter and check the output when Cold vs when Hot.
    2) Using you meter check the plug wires.
    3) Throw in a new set of plug to see if there is a change.
  7. R. Lewis

    R. Lewis Senior Member Retired Moderators

    Has this been an issue since you first got the scoot or just recently started doing it / did you buy it with the mods done already?
    Potential coil problem? Do you know if carb had any recent work done on it?

    BUBBIE Well-Known Member

    This above are Much NEEDED questions to answer here....

    I would also like you to Just check the pumping with the air filter OFF and see IF the accelerator pump is Squirting a full amount of fuel directly Into the carb when you twist the handle...

    Also you might want to replace the screws that hold the float bowl while carb is OFF or on.... Going to 5/8" long ""allen headed screws"" make it easy to remove the bowl for jet changes while on the manifold and NO removal of carb needed... EASY!

    I think the straight pipes are the Biggest problem here... NO back-pressure will make any HD motor Hard to start..(.)

    I have tried the lesser back-pressure on my 2000 carbed bike and the same thing "Problemed it".. until I went back with a better muffler system with some Back Pressure,,,,,, It did start easier!..

    I went with Python 3's---- 42 mikuni and liked Both....BUT nothing wrong with a good functioning HD Carb.

  9. Broiler

    Broiler New Member

    Thanks for all the help.

    Im guessing it may be running a bit rich and/or have an accelerator pump problem. Be checking it out when I get home. Bike only has 25K on it. I did put pipes on it recently but I replaced strait pipes with strait pipes so I think its no factor.

    Did get complaints from riding buddies that they smell a bit of gas when they ride behind me. I told them to ride faster or trade up for a bicycle.