BOSCH pluts - veeDUB

BOSCH pluts - veeDUB

Motorists who

know prefer

BOSCH pluts


in Germany


Tht Plug Boy

will tell you why



lOSCH spark pluts have insulators

of the hithnt qMiity


Years ago, lho Robert Bosch GmbH

introduced a now spork plug loch·

nique with tho Pyronit insulator

which is similar to synthetic ruby -

a jewel among spark plug insulators.

Every green

rings - assures you of o plug wifh fho reliable Pyronil




BOSCH spark 'lugs ore tile leading

spark plugs for general and sports use

Not only in automobile and motor·

cycle racing, in reliability frio Is, ond

in wOtld record events, but also in

everyday use, BOSCH spork plugs

consisfenlly provo lhoir dependo·


The famous world record holder, Juon Manuel Fangio

of Argentino on Mercedes-Benz, ond lhe motorcycle

world champions Hoos on NSU and Noii-Cron on

BMW, oil depend on BOSCH spark plugs.

.. _



A sporlc plug has to work under

most uwere. conditions. For thou·

sands of miles on end, it hos to

supply every cylinder with 30 to fiJ

ignition sparks a second. In 10 000

miles for example, this amounts to

30 to fiJ million sparks. At the some

time, the electrodes and the insula·

tor hove to withstand temperatures

of 500 c to 800° c and explosion

pressures up to60otmospheres(ovor

850 lb.fin2). BOSCH spork plugs

stand up to such extremes of tem·

perature and pres.s.ure as well as to

the corrosive oelion of the burnt


Whtn stltcting a spark plug- makt sur<


The stole of the plugs gives o clear

indiCation of tho slate of the

engine - provided always tho! the

correct type of plug is used. Tho

expert caracttristict

.. _


The engine is in good

shape if tho plug olec·

lrodes and body shaw

only slight oil or cor­

bon deposit (figure A)

or if the insulator

hos a sltghtly brownish

oppeoronc:e or hos

o slight yellow-brown

powdery deposit on

11. If the insulator is

covered with o vel­

vety, dull-block, dry


carbon deposit, mis·

firing is to be expect­

ed (Figure B).

Possible causes: (1) Ex·

cess of fuel - too rich

mixture, or choke clos·

ed too long; (2) thermal

ct.oroderishcs of plug

too high; (3) too big o

spark gop, for example,

through burning away:

(•J leaking valves.

8 (


"'· /;;; .._ '\ .

«' .,.

,. . -) f•

' , \.. . .







If the plug face shows

o shiny black moist,

deposit of carbonized

oil ond soot, mi.sfiring

is again to be expect­

ed (Figure q. Possible

causes: (l) cylinder

wear or badly fitting

ptston rings; (2) excess

of oil in engine or, in

two-stroke engines, ex·

cess of oil in fuel.

If the insulator is burn­

ed while or ifitand the

body show brownish·

tinted, fused, vitreous,

coked deposit, the plug

hos been overheolod

(pre-ignition: Figure D).

Possible causes: (1)

Thermal d!orocteristics

too low, (2) weok mix·

lure; (3) plug not light

or not firmly screwed

in; (•)valves not closing

properly or 1ncorrect

timing of ign1tion.

10000 milts At IAttll - this will m•kt yo•r tnzint J••nt AgAin

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