Question about kawasaki Fh641v 21hp 21 Hp Riding Lawn Mower Engine ()

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I have a HusqvarnaYTH1848XP lawn tractor with a KawasakiFH531VA41518 engine fitted. I have had coil problems in the past and have replaced both. The engine is now running roughly with loss of power and disconnecting both coils makes no difference. It will run ( poorly) without either lead attached ( both leads off). Where can the spark be coming from? Dave

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Hi david

need more info , your description says that engine will run without ht leads being connected to plugs ?

most times if plugs are connected and key turned off , engine will run on then eventually stop and can sometimes even reverse its rotation when it does so which is known dieseling or run on

if the plug leads are off and the engine continues to run the only way it may run is if it has carbon glowing on the piston top or cylinder combustion chamber


Ignition Theory of Operation

Mounted to the periphery of a flywheel are a pair of magnetic poles (south leading in clockwise rotation), generated by

a permanent magnet. By rotating the flywheel (magnetic poles) clockwise past the ignition module on a laminated core group, a voltage is generated in the primary winding (L1).


This generates a small bias current to flow through the control resistor (R1) to the base of (Q1). This base drive causes

the transistor to conduct (turns on) completing the primary circuit. Current flows from the high side of the primary winding

through the transistor (collector to emitter) to ground.


The trigger sensor (TS1) senses the optimum time (peak current) to remove the base drive from the transistor (Q1).

This abrupt "turning off" of the transistor causes an interruption in current flow which allows its associated flux collapse,

and several hundred volts is induced through the primary winding (L1) inducing a very large voltage in the secondary

winding (L2).


When the secondary voltage reaches several thousand volts the spark plug (SP) gap is ionized and ignition

occurs. The placement of the trigger sensor internal to the ignition insures constant timing over speed and temperature

and prevents counterclockwise operation.


The diode (D1) in the ignition shut off circuit blocks inadvertent application of battery voltage, protecting the internal

components of the ignition. With the stop switch (SW) in the closed position primary voltage is routed to ground, preventing ignition operation.

has anyone had the wiring connectors apart in / and around ignition and charging systems?

this problems is very strange

please get back to me

cheers pauly46

Posted on Apr 03, 2011

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