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I have a 2014 CRF250L dual sport motorcycle, the ignition fires

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every 720 degrees or rotation...
I have a 2014 CRF250L dual sport motorcycle, the ignition fires every 720 degrees or rotation, how does the ECM decide when to fire the ignition without a cam position sensor?
Submitted: 2 years ago.Category: Motorcycle
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Answered in 2 hours by:
5/9/2015
Motorcycle Mechanic: Louie, Technician replied 2 years ago
Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 12,789
Experience: 25+ yrs. experience
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Hi and welcome to JustAnswer,
Thank you for the question and your patience. Should you still need assistance for information purposes only...
Initially, the CRF250L uses a CKP (crankshaft position) sensor. This sensor is co-located at the stator/alternator area and sends pulses to pin 23 of the ECM.
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Customer reply replied 2 years ago
that gives a signal every rotation of the crank, the ignition coil only fires every other rotation of the crank, the service manual does not say how that is determined.
I have a electronic tachometer, that is how I discovered the firing interval.
Motorcycle Mechanic: Louie, Technician replied 2 years ago
Is the electronic tachometer calibrated/designed for a single cylinder/motorcycle engine? ...or for 4 or more cylinders.
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Customer reply replied 2 years ago
it is a bike master (266266) combination hour meter tachometer made by KOSO, and it is capable of multiple cylinders.
it came set for 1 pulse per revolution but it indicated twice the actual engine speed. it showed a warm idle speed of nearly 2900 RPM, changing the setting to 0.5 pulse per RPM brought the indicated engine speed down to where it needed to be with a indicated warm idle of 1420rpm, what the factory manual calls for the idle to be.
Motorcycle Mechanic: Louie, Technician replied 2 years ago
I understand.Still, the location of the 720° is the same as that of the 360° and the 0° hence if it fired in 720° position, then it would have also fired on/during the 360° and the 0° positions.It would not be practical nor possible for a single cylinder engine to fire on every second rotation of the crank.Based on the above, the engine is firing every 360° actual.
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Customer reply replied 2 years ago
I would have though so also, and the instructions for the tach stated that single cylinder engines normaly fire every rotation of the crank shaft, but it did not read correct and they programed the tach to work on engines that fire every other rotation like Honda small singles like the mini trail that are triggered by the cam shaft.
Motorcycle Mechanic: Louie, Technician replied 2 years ago
The "...changing the setting to 0.5 pulse per RPM..." would be very significant as it would also refer to halving (X 0.5) the reading for the 720° or = 360°.
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Louie
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