50cc Bystarters

[kev]

Has anyone noticed that the aftermarket bystarters are 20 ohms. The OEM ones are
around 5 ohms plus the series fixed resistor of 5 ohms. This gives the 10 ohms the
manual states as max. value. The 20 ohm one I tried never closed off the fuel
enrichment. Kev

[mousewheels]

I have not measured an aftermarket bystarter, but years ago tried one with poor results.

I wonder if a measurement with/without the 5 ohm external resistance would show additional extension?

[kev]

I measured the resistance by nicking the wires right at the bystarter coil. I bought this
bystarter new. I also bought a complete carb for my elite. The new carb bystarter also
checked in at 20 ohms. If a person got into dire straights I wonder if the alternator would
support a voltage double circuit to drive the 20 ohm bystarters.This would infact double
the bystarter load on the alternator. Kev

[mousewheels]

The bystarter is a thermal device, power into it is just converted to heat. In the OEM design, half the power is wasted in the external reisistor.

Thus aftermarket vs OEM bystarter resistance may look way off, but power into the aftermarket bystarter is comparable when no external resistor is used.

Calculate the power into each bystarter:

-- OEM --
Current = E/R = 12volts/( 5 ohms (bystarter) + 5 ohms (external resistor)) = 1.2 amps
Power = E * I = 6 volts (across bystarter) * current

-- Aftermarket --
Current = E/R = 12volts/20ohms = 0.6 amps
Power = E * I = 12 volts * Current

-- What's your results? --

[kev]

I see your point and I agree. The bystarter being resistive would use thermal expansion to
move the needle. For some reason I thought the bystarter was magnetic and would use
amperturns to move the needle to the center of a coil. Thanks Mousewheels for the
good infomation, I still have a lot to learn about scooters.
Kev

[twistedtuner]

The bystarter is a thermal device, power into it is just converted to heat. In the OEM design, half the power is wasted in the external reisistor.

Thus aftermarket vs OEM bystarter resistance may look way off, but power into the aftermarket bystarter is comparable when no external resistor is used.

Calculate the power into each bystarter:

-- OEM --
Current = E/R = 12volts/( 5 ohms (bystarter) + 5 ohms (external resistor)) = 1.2 amps
Power = E * I = 6 volts (across bystarter) * current

-- Aftermarket --
Current = E/R = 12volts/20ohms = 0.6 amps
Power = E * I = 12 volts * Current

-- What's your results? --

-----------------------------------------------
So what you are saying is that technically the new choke without the stock resistor will actually use LESS current but ohms law says that it will be replaced with More POWER ?
If this stays under the 12v range then shouldn't hurt the engine charging system right? Less Current draw is healthy no?
I will Have to see what my "new" choke is at I guess.
If its resistance cold is greater than the 5 or 10 ohms then probably can get away without the stock resistor?

[Bear45-70]

The bystarter uses AC from the alternator, that way it only functions when the engine is running. If you hook it to DC, any time the key is on the bystarter will heat up and close off the extra fuel.

[twistedtuner]

The bystarter uses AC from the alternator, that way it only functions when the engine is running. If you hook it to DC, any time the key is on the bystarter will heat up and close off the extra fuel.

That ok as long as when it don't start or its cold you don't leave the key on, without engine running.
I have a 150cc Automoto as wel, andl that thing uses a d/c hookup like this. Has been a problem before but learned not to leave key on.....
No matter looks like I may need a choke and a resistor. Mousewheels confirmed I should be able to just get aftermarket one, and be good to go.

[Bear45-70]

The bystarter uses AC from the alternator, that way it only functions when the engine is running. If you hook it to DC, any time the key is on the bystarter will heat up and close off the extra fuel.

That ok as long as when it don't start or its cold you don't leave the key on, without engine running.
I have a 150cc Automoto as wel, andl that thing uses a d/c hookup like this. Has been a problem before but learned not to leave key on.....
No matter looks like I may need a choke and a resistor. Mousewheels confirmed I should be able to just get aftermarket one, and be good to go.

If your after market bystarter have 20 ohms, why would you add more ohms to the circuit and slow down the bystarter function? Time the thing with a test to see how long it takes it to extend and if it is longer than the Honda one, then put a 20 ohm resistor in parallel with the bystarter, that will cut the ohms in half and speed up the bystarter function.