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NotTaR of small Gasoline Engines and Rotary Lawn Mowers : Starting the mower
Copyright ©
1994-2007, Samuel M. Goldwasser. All Rights Reserved. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying.
I may be contacted via the Sci.Electronics.Repair FAQ (www.repairfaq.org) Email Links Page.
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Most mowers and other small pieces of gas powered yard equipment use a self
retracting recoil type starter. You pull on a handle attached to a cord wound
around a one-way clutch affair. Pulling on it rotates the engine's crankshaft
and the clutch allows the engine to run without pulling you back into the
mower! If yours has an electric starter, then you don't need to tug on
anything - plug it in and push a button or turn a key. Of course, finding
an outlet at the far end of a large yard may prove to be a challenge. With
larger equipment like riding mowers, power is usually provided by an on-board
rechargeable battery. In either case, there will be some kind of backup
recoil or rope starter should the electric start be unusable or inconvenient.
For the following, we will assume you pull a self-retracting starter rope.
With an electric starter, replace the words: 'pull...times' with 'crank for
several seconds'.
Move the mower or other equipment to the place where it will be used - no
sense in dragging a chugging lawn mower through the neighborhood. Position
it on a solid level surface. Make sure there are no loose stones, twigs,
branches, logs, etc. underneath to get sucked up and thrown about once you
succeed in getting the engine started (if you ever do).
When attempting to pull on the starter cord, it may be helpful to put one
foot on the mower deck to brace it. Whether this is needed will depend
on the design of your mower and in what direction the cord exits from the
starter.
You or the starter motor supplies the power to get it started. However,
at the low speed of starting, special modifications may be required to the
fuel system for the engine to catch. These may take one of the following
forms:
- Primer - a rubber bulb or pushbutton squirts a little extra gas into
the intake pipe. Your engine manual will detail the procedure and number
of 'pushes' required under various conditions - typically between 1 and 12.
Too few and nothing will happen. Too many and you will flood the engine
(excess gasoline will prevent it from starting). See the next section.
A typical starting procedure for an engine with a primer might be:
- Set the throttle control (if any) to the START or HIGH position.
- Push the primer 5 times.
- Pull the starter cord once or twice (if it doesn't start on the first
one).
- If it still doesn't start, prime 2 more times.
- Pull the starter cord again.
- Set the throttle control to the desired speed once it starts.
- Automatic primer - a chamber in the carburetor which fills with the engine
stopped and provides an additional squirt of gas when starting.
Automatic choke - temperature and engine vacuum control the fuel-air mixture.
A typical starting procedure for an engine with an automatic primer
or automatic choke might be:
- Set the throttle control to the START or HIGH position.
- Pull the starter cord once or twice (if it doesn't start on the first
one).
- Set the throttle control to the desired speed.
- Choke plate - a control on the carburetor which partially closes off the
air intake and forces additional suction to increase the amount of fuel
drawn into the cylinder. Normally, the choke is closed when starting
cold and gradually opened in the few seconds after the engine starts. It
is left fully open once the engine is running and may not need to be closed
when starting warm.
A typical starting procedure for an engine with a choke might be:
- Close the choke (usually on carburetor).
- Set the throttle control (if any) to the START or HIGH position.
- Pull the starter cord once or twice (if it doesn't start on the first
one).
- If it still doesn't start, open the choke half way.
- Pull the starter several more times until it starts (hopefully).
- Gradually open the choke to keep the engine running smoothly.
- Set the throttle control to the desired speed.
If the appropriate procedure is not successful, the engine may be flooded.
You can give it 15 minutes or so for the gas to evaporate and try again or,
if there is an IDLE or LOW speed position, open any choke and pull the rope
several times in this position which should clear out the excess gas. Then
repeat the recommended starting procedure.
If none of this works, you may have a starting problem and should refer to
the section: Lawn mower will not start. Probably,
you forgot to fill the gas tank!
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