Four stroke single cylinder motorcycle spark plug firing


7 replies to this topic
  • slow450

Posted July 10, 2008 - 11:44 AM

#1

On a four stroke single cylinder motorcycle does the spark plug fire on each revolution? Since the coil is triggered off the flywheel it would seem that the plug fires on every rev not like an automobile engine that fires on every other rev. The real question is if you use a portable tachometer that is triggered off the spark plug wire is the indicated RPM (meter reading) the actual engine RPM or is the indicated RPM half of the actual engine RPM?

  • E-man811

Posted July 10, 2008 - 11:47 AM

#2

Yes it does.

On the portable tach, or an hour meter, you would tell it if it is 2 or 4 stroke and how many cylinders.

Ride safe

Ian

  • zuch95701

Posted July 10, 2008 - 11:49 AM

#3

the vast majority of the 4 stroke engines on the market well only fire on the power stroke. All modern high perfornace engines use a ingition modual that controls the spark. However, there are a few smog motors out there that will fire on both power and exhaust stroke. THis helps burn any unburnt fuel in the motor. More than likly your bike is only power stroke so you are good to use a induction rpm tester to measure your rpms.

  • zuch95701

Posted July 10, 2008 - 11:52 AM

#4

one more note. Most dirk bike engines do not time the spark plug of the coil. The coil is a charging sytem that provides the energy for the coil to fire. They are not a magnetic pick up like your timpical briggs or 5hp honda motor.

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  • slow450

Posted July 10, 2008 - 12:12 PM

#5

Does a four stroke KTM only fire on the power stroke? How does that work if is triggered off the flywheel.
Slow

  • klxd

Posted July 10, 2008 - 12:21 PM

#6

Gotta disagree zuch. How does the ignition module know which stroke the crank is on.

If it has a crank trigger it's going to fire every stroke unless it has some sort of sensor on the cam. Some bikes, like XR200's have the ignition trigger on the cam and only fire on the power stroke.

  • mkporn

Posted July 10, 2008 - 12:26 PM

#7

the vast majority of the 4 stroke engines on the market well only fire on the power stroke. All modern high perfornace engines use a ingition modual that controls the spark. However, there are a few smog motors out there that will fire on both power and exhaust stroke. THis helps burn any unburnt fuel in the motor. More than likly your bike is only power stroke so you are good to use a induction rpm tester to measure your rpms.



You are incorrect. The motor does fire 2 times. It fires once on compression and once on exhaust. The pick up for triggering the spark is on the flywheel and triggers a spark. The ignition does not care if the motor is on intake, exhaust, power or compression stroke. Infact, to prove this you could put the bike on top dead center, remove the cam chain and turn the crank over 180 degrees, put it all back together. The motor will fire right up with out problem. :thumbsup:

  • mkporn

Posted July 10, 2008 - 12:28 PM

#8

Gotta disagree zuch. How does the ignition module know which stroke the crank is on.

If it has a crank trigger it's going to fire every stroke unless it has some sort of sensor on the cam. Some bikes, like XR200's have the ignition trigger on the cam and only fire on the power stroke.


you are absolutely correct. The pick-up is mounted righ on the head behind that cover that is marked CDI on a XR200 and many more honda motors.:thumbsup:





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