New Mexico state record. (Santa Fe, N.M.) 1914-19??, 1920-10-22
BUCK|NC
AT SLOW SPEEDS
Many Small Adjustments Are
Needed to Remove Play and
Insure Smoothness.
JERKING HARMFUL TO AUTO
Mlsfiring Reduces Power Of Engine to
Such an Extent That Car Must
Naturally Run With Most
Uncomfortable Motion.

During the last few weeks the
writer has received n great number of
inquiries in which owners complain
that the car bucks or jerks at low
speeds. This condition Is not only I'M
comfortable for the passengers but 1t
is detrimental to the car, says a writer
in Chicago Tribune. The ordinary
garage mechanic-I mean the 'gyp"
sort-usually cannot make a proper
diagnosis, and he cures the trouble
only after he has taken the car half
apart. IL your car bucks, and you
cannot determine the cause after read
ing this article, have a competent
service la drive the car.
A car in perfect mechanical condi-
ton throughout will throttle down to
five or four or even three miles an
hour and pull evenly, but let there be
misfiring and Immediately the whole
car starts to jerk. The misfiring so re-
duces the power of the engine and pro-
duces such lapses in the power i'm
pulses that the car must naturally run
Will II JtlhN lioliois III hBliiNo w
all cars, whether new or old. When
ever the engine cannot develop enough
power to pull its load 1t falters just as
a horse will tighten and then permit
slack in the traces. You would do the
same thing If you were dragging a
heavy load. A carbonlzed engine can
not develop full power with a given
throttle setting. Poor ignition, poor
carburetion, improper valve timing, or
any abnormal engine condition is like
ly to reduce the power and make the
engine falter. 1t might ever stall.
Common Cause Of Trouble.
But apart from the engine there are
other causes of this common trouble.
The commonest is due to too much
play between the driving pinion and
the large bevel gear or ring gear in
the axle. 1t may, however, be due to
excessive play anywhere in the driv-
ing system from the clutch TO the rear
wheels.
When the engine Is under load and
pulling, all the parts that move are
tight. This includes engine parts
clutch, transmission, axle. They tight
en- like the traces tighten when a
horse starts to pull and continues to
pull. SO long as this pulling continues
there will be no noise, because the
parts are tight against each other. If
they were not they could not pull. In
a car that bucks due to excessive play
in the driving system the same effect
practically may be had by slowing
down and suddenly accelerating. This
may be done by closing the throttle
suddenly at 20 miles an hour and
then suddenly opening 1t again.
At low speeds, however, 1t does not
require a great amount Of extra play
to cause a knock and the Objectionable
bucking. A clutch that has a worn
plate and weak springs will slap
against the fywheel and give the buck
ing effect. A worn clutch shaft or
worn clutch bearing would cause It.
Shaft Must Not Move.
In the transmission the main shaft
must not move back and forth, for If
1t does it will cause a knock, though
1t may not cause bucking, due to the
fact that the movement is not trans
mitted to the other parts.
Universal joints with worn sliding
members or worn bushings on the
spiders will cause bucking. If the
sliding shaft is not worn play else
where in the joint may be taken up
and not noticed except as an occasion
al knock.
In the case Of wire wheels 1t often
happens that the wheel driving men,
bers become worn, giving the same eff
feet as though there were play in the
differential. If a wire wheel is not
tight in place 1t will slap sideways and
this knocking often is mistaken for a
bucking rear end.