Hard to Start When Hot.....Carb?

Discussion in 'Troubleshooting & Diagnosis' started by gordonquixote, Aug 16, 2009.

  1. kenny77

    kenny77 Veteran Member Lifetime Gold Member

    Jul 31, 2001
    Ft. Lauderdale, FL
    No way, I would have found that right away and carb is brand new 650 AVS. Did the same thing with my 670 street avenger.
  2. dynobrat

    dynobrat Veteran Member

    May 28, 2009
    Ontario, Canada
    I have the same issue. I thought about insulating the fuel line so the fuel is cooler going into the carb. Maybe that might work?

    I have a glass fuel filter and when the engine is hot, you touch the filter and it's reasonably warm, so when it sits in the bowl it gets hotter that much quicker. I don't know if that will solve the problem, but it's publicly embarrassing.
  3. Scatter

    Scatter Veteran Member

    Jun 26, 2003
    Millbrook, Al
  4. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

    Jun 22, 2003
    Endicott, NY
    Usually, it's heat soak that boils the fuel in the carb = hard starting when warm. The best cure for it is to insulate the carb from the intake. Usually that's accomplished by a thicker intake to carb gasket that has hard spacers where the studs pass through (spacers are thinner than the gasket material). Then there's the carb spacers that are either made from hardwood or a phenalic (sp?) which require a gasket between the carb & spacer along with a gasket between the spacer and carb.

    Q-jets are prone to hard starting when warm because the welch plugs in the bottom of the main body of them get loose. The symptom of this is: cold start is normal. Hot start you have to hold the accelerator to the floor and you smell raw gas when it does start. Fuel mileage is crap. The fix is to rebuild the carb and when doing so either epoxy the welch plugs with an epoxy that is impervious to gasoline (like Hysol) or to put that funny looking block of rubber (that nobody knows what it is) in between the base & main body of the carb to in effect, seal the welch plugs. Here is a link to a picture of a complete gasket set where you'll see that funny looking gasket in the upper right hand corner: http://www.gesslerheadporting.com/members/gesslerheadporting/ghp.nsf/GHP-Q5150!OpenPage
    Last edited: Aug 18, 2009
  5. gordonquixote

    gordonquixote Veteran Member Lifetime Gold Member

    Jul 18, 2006
    Tallahassee, FL
    Man - I can't put a spacer in between my carb/intake. I have about 3/8" between the air cleaner nut and the hood at this point.

    I was hoping you guys would say turn a magic srew 1/2 turn out or something.

    Or timing?
  6. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

    Feb 26, 2004
    Bloomington, MN
    Don't feel bad, Gordo.... My Q-jet does it too.
    Cold or hot it fires in a blink.... It's the in-between temps which tend to flood it. :(
    (The plugs are already epoxied too.)
  7. woody80z28

    woody80z28 Veteran Member Lifetime Gold Member

    Sep 8, 2004
    walton, ny usa
    Mine is very similar. Stupid carbs.

    Fuel injection should fix it!
  8. High Country Z

    High Country Z Veteran Member

    Fuel percolation. This fuel doesn't work well in carb. engines.

    Does anyone know of any fuel additive that stops this?
  9. dynobrat

    dynobrat Veteran Member

    May 28, 2009
    Ontario, Canada
    welcome to the antiquated world of carburetion
  10. Displaced Hokie

    Displaced Hokie Member

    Aug 13, 2009
    Birmingham, AL
    Has anyone had a car that used to be OK and then start doing this when they started with the 10% ethanol fuel? I'm betting that is the culprit.

Share This Page