my chinese 100cc two stroke has an electric choke, can someone confirm how/when it is powered on and off?
it looks like it is always on choke until the solonoid is powered up which turns the choke off, is that correct? also i cant see a sensor so how is the choke turned off? is it simply a case of when the stator is charging?

thanks

 

You are correct. The choke is always on unless it is powered up and then (when powered) heats up and turns off.

When the engine is cold the choke is on. An extra fuel passage is opened up and allows the fuel/air ratio to be enrichened by adding more fuel. Note that this is opposite from the standard "choke" method where the fuel/air ratio is enrchined by "starving" the mixture of air.

When you start up the quad 12 volts of some sort is applied the choke (which is more correctly called a "by-starter valve" BTW). Note that the 12 volts powers a choke heater - it is *not* a solenoid - its just a heater that warms up over a minute or so. The heat expands a wax pellet that pushes closed a valve and blocks the extra fuel passageway.

The choke heater is designed to be powered by 12 volts. But there are a couple ways this is accomplished:

1) The power comes from an alternate 12 volt output from the regulator. This power is a little different from just hooking it to power from the ignition switch. The regulator only delivers power when the engine is running. After all it gets its energy from magnets moving past coils of wire in the stator. So if the engine is stopped the output of the regulator is zero volts. So the choke only warms when the engine is running. This isn't quite the same as powering it from the 12 volt battery power from the ignition switch when turned on. That would work too, unless you turn on the ignition switch (starting the choke action), delay pressing the start button for a couple minutes, then try to start the quad. At that point the choke is already off, and the quad won't start. The auxillary output from the regulator solves this problem because the choke is only powered once the engine starts.

2) The power comes from AC voltage directly off the stator (the raw AC voltage going to the regulator). This too works because it also only provides voltage to the choke when the engine is running. [When it comes to heating stuff it doesn't matter whether the voltage is AC or DC. It works the same. A 110 volt AC light bulb will work exactly the same if powered from 110 volts DC.] But there's a problem... The voltage here is unregulated and varies widely with engine speed. So usually a resistor is added to limit the current at high engine RPM to keep the choke heater from burning up. But at low RPM the heater is slow to close. But that is also an advantage.... If you start up the quad and let it idle, the choke closes slower, and at the same time the engine is warming up slower. If you start up the quad and take off at high speed right away, the choke closes faster (with the higher applied voltage), but the engine is warming up faster too.

Here is a troubleshooting guide to testing your Bystarter valve (auto choke):

http://www.anythingatv.com/Technical...CCHOKETEST.pdf

 

thanks! that all makes sense

 

Curious about this electric choke situation. And a couple questions. Why is a one nipple intake needed as a vacuum on the gy6 engines? And second and more important is it even possible to swap out a electric choke carb for a cable choke or manual carb?