New to the busn, few mower questions

Discussion in 'Lawn Mowing' started by Shappie, Jul 5, 2011.

  1. Shappie

    Shappie LawnSite Member
    Messages: 44

    I am new to the business. I purchased an older Gravely Pro-150 36" belt drive for a very good price (Kawi 12.5hp FB460a motor). Got it home, changed the oil, fuel filter, fuel, and greased it up. I have a few problems:

    1- It is pulling to the left. (tire pressure is =) belts on the left are sagging more than the right so I am hoping thats the easy fix..

    2- It is a pistol grip control. How far are the levers typically spaced from the handle? (I have big hands and seem to reach an uncomfortable distance to squeeze the brake/clutch)

    3- If I have a clean carb and filter, new plug, good spark, and compression at the plug opening, could it occasionally not starting simply be bad gas, or am I overlooking something. (gas is from early this year...)

    I know these are simple questions for you pro's that read this, so I appreciate your advice in advance. I just need to know if its cheaper or easier to just take it to the service center for repair (because I don't even know how much that typically costs...) THANKS AGAIN!!

    (P.S. I am aware that you get what you pay for... but I'm hoping to use this as a starter mower...)
  2. Bumpmaster

    Bumpmaster LawnSite Fanatic
    Messages: 22,383

    Starting trouble, make sure the choke is in the correct position. Like do it manually not up by the control panel, down next to the engine.:cool2:
  3. Shappie

    Shappie LawnSite Member
    Messages: 44

    Thanks, it fires right up, it seems sluggish to restart while somewhat warm..
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  4. Bumpmaster

    Bumpmaster LawnSite Fanatic
    Messages: 22,383

    Ya, I get that as well.
  5. Snapper Jack

    Snapper Jack LawnSite Senior Member
    Messages: 525

    If the choke is set up accordingly,the FB460 should fire up on first or second pull(Most of the time) or it needs a good tune up. Untill the motor reaches it's hi temp,you'll need to choke assist it,from my experiences.
  6. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Why my engine won't start in the heat after it's been running?
    Could winter fuel affect my engine in the summer?

    Vapor lock

    Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines.

    It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult. The fuel can vaporise due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of "winter" fuels during the summer can cause vapor lock to occur more readily.

    1] Causes and incidence

    Vapor lock was far more common in older gasoline fuel systems incorporating a low-pressure mechanical fuel pump driven by the engine, located in the engine compartment and feeding a carburetor. Such pumps were typically located higher than the fuel tank, were directly heated by the engine and fed fuel directly to the float bowl inside the carburetor. Fuel was drawn under negative pressure from the feed line, increasing the risk of a vapor lock developing between the tank and pump. A vapor lock being drawn into the fuel pump could disrupt the fuel pressure long enough for the float chamber in the carburetor to partially or completely drain, causing fuel starvation in the engine. Even temporary disruption of fuel supply into the float chamber is not ideal; most carburetors are designed to run at a fixed level of fuel in the float bowl and reducing the level will reduce the fuel to air mixture delivered to the engine.

    Carburetor units may not effectively deal with fuel vapor being delivered to the float chamber. Most designs incorporate a pressure balance duct linking the top of the float bowl with either the intake to the carburetor or the outside air. Even if the pump can handle vapor locks effectively, fuel vapor entering the float bowl has to be vented. If this is done via the intake system, the mixture is, in-effect, enriched, creating a mixture control and pollution issue. If it is done by venting to the outside, the result is direct hydrocarbon pollution and an effective loss of fuel efficiency and possibly a fuel odor problem. For this reason, some fuel delivery systems allow fuel vapor to be returned to the fuel tank to be condensed back to the liquid phase, or using an active carbon filled canister where fuel vapor is absorbed. This is usually implemented by removing fuel vapor from the fuel line near the engine rather than from the float bowl. Such a system may also divert excess fuel pressure from the pump back to the tank.

    Most modern engines are equipped with fuel injection, and have an electric submersible fuel pump in the fuel tank. Moving the fuel pump to the interior of the tank helps prevent vapor lock, since the entire fuel delivery system is under positive pressure and the fuel pump runs cooler than if it is located in the engine compartment. This is the primary reason that vapor lock is rare in modern fuel systems. For the same reason, some carbureted engines are retrofitted with an electric fuel pump near the fuel tank.

    A vapor lock is more likely to develop when the vehicle is in traffic because the under-hood temperature tends to rise. A vapor lock can also develop when the engine is stopped while hot and the vehicle is parked for a short period. The fuel in the line near the engine does not move and can thus heat up sufficiently to form a vapor lock. The problem is more likely in hot weather or high altitude in either case.

    Gravity feed fuel systems are not immune to vapor lock. Much of the foregoing applies equally to a gravity feed system; if vapor forms in the fuel line, its lower density reduces the pressure developed by the weight of the fuel. This pressure is what normally moves fuel from the tank to the carburetor, so fuel supply will be disrupted until the vapor is removed, either by the remaining fuel pressure forcing it into the float bowl and out the vent or by allowing the vapor to cool and re-condense.

    Vapor lock has been the cause of forced landings in aircraft.
    From Wikipedia, the free encyclopedia
    Last edited: Jul 5, 2011

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