TC96 EFI Starts Hard when Hot

Discussion in 'Engine, Fuel and Exhaust' started by VTBen, Mar 29, 2012.

  1. VTBen

    VTBen Member

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    Hi all,

    Have a question for you. I just picked up an 08 Fat Bob. With only about 6k miles the bike rides like new but has one problem I want to work on. When it's cold it starts fine but if it's hot it doesn't. (I'm talking about hot as in I've been riding it for 20 min plus, not ambient air temp.) It will start but if I don't open the throttle a bit it will crank 6-8 times before catching.

    If it's hot and I open the throttle a quarter turn or a little less it fires right up, so I'm thinking my cranking fuel is just set too low? I've been playing with my TTS Mastertune and these are the values for cranking fuel:



    Temp C mS
    -16 65.0
    0 50.4
    20 35.6
    32 24.8
    48 19.5
    64 16.1
    80 15.1
    96 14.1
    112 13.6
    128 13.3
    144 13.1
    160 13.1

    (Note: These are original to the bike. I haven't changed them and the hard starting predated any tuning I did.)

    So I'm thinking I need to tweak these but am looking for feedback on how much. I thought I might start by increasing the lower ones by .5 and the 80-160 temps by 1.

    For those who have worked with this does that sound about right?

    Thanks,

    Ben
     
  2. Monsterbob

    Monsterbob New Member

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    Same Thing
     
  3. Hoople

    Hoople Account Removed

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    How I see it.
    By giving it a little throttle at cranking, you are really only giving the engine more air and not fuel. A throttle body only provides the air. The Map provides the fuel. The TPS position doesn't get involved until the engine is running.

    Only my guess, but increasing cranking fuel should actually make it worse.
     
  4. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Have you tried getting a can of carb spray and cleaning the IAC really well? I use about 1/3 can with a 10 min break between sprays until the can is used up. Best to use a bib down the side of the engine/tranny to keep the fluid off those bits. Also, I stuff a wad of paper towels up against the butterfly to try and stop so much fluid running in the cylinders. Help to lean the bike to the right.

    I would also suggest making sure all the battery cable connections are tight (wouldn't hurt to wire brush the mating surfaces).

    TQ
     
  5. Jack Klarich

    Jack Klarich Expert Member

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    Add some Amazon.com: NAPA Sil-Glyde Silicone Lubricating Compound 8 Ounce Tube: Automotive To the connections to make them weather proof
     
  6. VTBen

    VTBen Member

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    Thanks TQ,

    IAC, is that the air cleaner? I just put on a new high-flow cleaner with a new filter, so that should be good.

    Ben

    Thanks Hoople,

    Nice thing about the TTS is I can fiddle with it all I want. Maybe I'll try lowering it a digit and see if that works better.

    Unfortunately the weather up here in VT just took a turn for the colder so it may be a bit until I get out for a good test ride to check it.

    Ben
     
    Last edited by a moderator: Mar 30, 2012
  7. Jack Klarich

    Jack Klarich Expert Member

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  8. VTBen

    VTBen Member

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    Gotcha. Thanks. I'll take a look at that.

    Ben
     
  9. FerrousBueller

    FerrousBueller Junior Member

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    Had a similar, ( but mild ) problem with my '09, At the 10K service I changed the spark plugs. Problem solved.

    That's the best I can do, hope that helps.

    Cheers!
     
  10. VTBen

    VTBen Member

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    Thanks TQ,

    Looks like you hit the nail on the head. I got some time to get in there yesterday with a can of carb cleaner and now it's running a whole lot better.

    It's funny, I didn't get that black gunk running out that others have reported. But on the other hand this is a five-year-old bike that only had 5k miles when I bought it so clearly it's been parked a lot. I wonder if something got stuck or gummed up in the IAC just from standing unused? Either way it's better now. Doesn't hesitate as much starting when hot and idles more smoothly than it used to.

    Think I'll add spraying that out to my list of routine maintenance.

    Ben