Why it happens: bike won't start, but buzzes.
#1
05-04-2008, 09:06 AM
Join Date: Dec 2007
Location: terrorizing southeastern norf carolina
Posts: 2,092
Why it happens: bike won't start, but buzzes.
this seems to be a popular one..lol
o.k., keeids.. heres WHY you get that wicked little buzz under your seat when trying to start your bike.
normally, in most situations, the root cause is a low voltage or available current from the battery. this, is resultant of abad connection or your battery being on it's deathbed.
the rapid clicking you hear is the solenoid (relay) for the starter acting like a door buzzer. that sound is the contacts chattering..
now.. What actually makes this happen in electrical reasoning.
these components are designed to operate at 12-15 volts. thats prety much an industry standard. the starter motor, relays, light.. everything is designed for the optimal power to be about 13.8VDC at whatever current it needs.
voltage and current are independant and inversly proportional. the higher the voltage is, the lower current you need.. thats why hi-tension transmission lines that have 750,000 Volts on them only have about 3 amps flowing thru them. when it gets transformed to a distribution voltage like 13.8KV, its about 15A or so..
thats why you can get a 5000A panel in industy for a 480 volt system.. 480 is low compared to the power that is actually generated.
the lower the voltage, the higher the current..
that being said, the starter on your bike needs a pretty massive amount of current to spin 2 or 4 cylinders fast enough to get it running.. (i think about 360RPM)
so.. you're not gonna put 50Aand 12V thru a tiny little start button.. the heat generated would instantly melt it. the start button feeds a "control voltage" to a solenoid or relay. the coil inside this relay barely pulls any power.. maybe an amp or so.. theres a set of contacts attached to a "plunger" inside this solenoid. when you hit that button, the coil makes a magnetic field that draws the (spring-loaded) plunger down to a ferric core, thus closing the contacts in the process. this is what passes the power from the battery to the starter. the contacts are rated for about 125-200% of the max load it'll see.. so, in actuality, they're oversized, but thats a good thing..
now..lets assume your battery is poop, and can't handle producing 13.8 or 12V. when you hit that button, the power is sent to the coil in the solenoid.. it closes the contacts, sending power to the starter.. the starter, being the amperage hog it is, puts a heavy-*** load on the battery, and the battery's voltage drops. now that the battery went from 12V or so to about 9 or 10 volts, the power is no longer there to support holding the spring-loaded plunger in place- the magnetic field is too weak now. the spring's force in the solenoid breaks the field's pull, and the contacts open, cutting power to the starter..
relieved, the battery's power suddenly accumulates exponentially, and the power is back again to be able to pull the solenoid's plunger in, and re-establish power flow to the starter..
once again, the starter pulls all the power, the voltage drops, and the solenoid open, cutting starter power..
and this all happens in a matter of milliseconds.
as long as you hold the button in, and theres enough of power availably to even pull the solenoid in, this will occur.
and that, my children, is why you get that stupid buzzy clicky sound.
this has been your electrical engineering theory lesson for the day.
there will be a test..
probably the next time this happens to you...lol
o.k., keeids.. heres WHY you get that wicked little buzz under your seat when trying to start your bike.
normally, in most situations, the root cause is a low voltage or available current from the battery. this, is resultant of abad connection or your battery being on it's deathbed.
the rapid clicking you hear is the solenoid (relay) for the starter acting like a door buzzer. that sound is the contacts chattering..
now.. What actually makes this happen in electrical reasoning.
these components are designed to operate at 12-15 volts. thats prety much an industry standard. the starter motor, relays, light.. everything is designed for the optimal power to be about 13.8VDC at whatever current it needs.
voltage and current are independant and inversly proportional. the higher the voltage is, the lower current you need.. thats why hi-tension transmission lines that have 750,000 Volts on them only have about 3 amps flowing thru them. when it gets transformed to a distribution voltage like 13.8KV, its about 15A or so..
thats why you can get a 5000A panel in industy for a 480 volt system.. 480 is low compared to the power that is actually generated.
the lower the voltage, the higher the current..
that being said, the starter on your bike needs a pretty massive amount of current to spin 2 or 4 cylinders fast enough to get it running.. (i think about 360RPM)
so.. you're not gonna put 50Aand 12V thru a tiny little start button.. the heat generated would instantly melt it. the start button feeds a "control voltage" to a solenoid or relay. the coil inside this relay barely pulls any power.. maybe an amp or so.. theres a set of contacts attached to a "plunger" inside this solenoid. when you hit that button, the coil makes a magnetic field that draws the (spring-loaded) plunger down to a ferric core, thus closing the contacts in the process. this is what passes the power from the battery to the starter. the contacts are rated for about 125-200% of the max load it'll see.. so, in actuality, they're oversized, but thats a good thing..
now..lets assume your battery is poop, and can't handle producing 13.8 or 12V. when you hit that button, the power is sent to the coil in the solenoid.. it closes the contacts, sending power to the starter.. the starter, being the amperage hog it is, puts a heavy-*** load on the battery, and the battery's voltage drops. now that the battery went from 12V or so to about 9 or 10 volts, the power is no longer there to support holding the spring-loaded plunger in place- the magnetic field is too weak now. the spring's force in the solenoid breaks the field's pull, and the contacts open, cutting power to the starter..
relieved, the battery's power suddenly accumulates exponentially, and the power is back again to be able to pull the solenoid's plunger in, and re-establish power flow to the starter..
once again, the starter pulls all the power, the voltage drops, and the solenoid open, cutting starter power..
and this all happens in a matter of milliseconds.
as long as you hold the button in, and theres enough of power availably to even pull the solenoid in, this will occur.
and that, my children, is why you get that stupid buzzy clicky sound.
this has been your electrical engineering theory lesson for the day.
there will be a test..
probably the next time this happens to you...lol
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