Gearbox causing hard starting

by Todd C Burrus in 912 / 914 Technical Questions 5 years ago

I do not understand how a bad gearbox can cause hard starting. One would think that a slipping gearbox would allow the engine to rev up faster and start easier. Can someone explain this to me?

Re: Gearbox causing hard starting

by Rob Seaton » 5 years ago

Rob Seaton

3 1.32k 240

One misconception: the clutch does not slip in normal operation, only with a prop strike, and just slightly at shutdown.
Once the gearbox get loose (springs no longer exerting enough pressure on the freeplay between the dogs) the dogs will slam back and forth with the piston pulses and inertia of the prop.
This gives a kickback just as the combustion process is trying to fire. With a really loose gearbox it is almost impossible to start.

Thank you said by: Ken Ryan

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Re: Gearbox causing hard starting

by Roger Lee » 5 years ago

Roger Lee

125 5.12k 4.52k

Hard starting common causes are:
Weak or too small a battery,
Carbs not synced,
Plugs too wide a gap,
Old black starter (it is worth your while to get the newer high torque gold colored starter),
engine temp just too darn cold,
poor starting technique,
or a combo of any of the above.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Gearbox causing hard starting

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