Blue wire Kill-switch/Anti-theft device.

It allways astonishes me as an electrical engineer that ignorant people,who know zilch about what large ac voltages can do to you,see fit for no discernable reason to mess around with the output of the power coill of the HT engines instead of running it directly to the CD unit.The white wire will kill the engine,that is its function and nothing untoward is going to happen to the coil .if it is shorted to ground.The high voltage blue wire output happens to be loaded with every possible kind of electrical garbage you can imagine,like high intensity audio magnetic fields which are very hard to shield against and which will mess up speedos&Hall effect sensors.You just don't want to cart it around unless you have to.Then there is the Radio Freq garbage produced by the Capacitor discharge that gets exported on it. Leave it alone.
 
The ignorant Turtle asks...so splicing a kill switch fully insulated into the blue wire is not a good idea?? I dont have a on board radio, speedo,or pacemaker...what is a hall effect censor..?? From what I have read on this forum it seems like the way to go..please explain in more laymans terms....you have a previous post here that says any good quality switch will work but be sure to protect yourself from the connection...thanks
 
Last edited:
As a antitheft device a switch on the blue wire,with it hidden close to engine &CD unit is not really that bad allthough you could accomplish the same objective with an extra switch to ground on the WW .I think it is bad practice and unnecessary to run wiring around with a couple of hundred volts on it to a switch up front on your handlebars.Hall effect sensors detect magnetic fields and are frequently used as position indicators.As a survivor of working in a High Voltage test lab,I am in principle against running unnecessary risks.
 
What do hall effect sensors that detect magnetis fields and are frequently used as posistion indicators have to do with putting a kill switch into the blue wire??
 
I installed a toggle switch inline on the black wire (ground) it kills the engine by depriving it of a ground source. Is this a bad idea? I know on cars when working on the electrical system your supposed to remove the ground cable from the batt. not the positive.
 
It works of course,but contrary to the battery situation you refer to in which there is no voltage to ground on the battery output,because the SOURCE (battery) has no ground return,here the source,the CDI generator coil in the engine is internally grounded.So there are allways high ac voltages on the blue and also on the black wire (when the kill switch is opened ),but that only lasts for a couple of seconds (until the engine dies),so it should be pretty safe.At least much safer than messing around with the blue wire,which ought to be left alone, IMO.
 
Last edited by a moderator:
I'm with DD on this one. Use the white wire to kill the engine. The blue wire has a couple of hundred volts on it when the engine is running, it can bite you pretty good.

I don't know how the rumor of damaging the CDI using the white wire got started, but there is absolutely no basis in this myth.

The CDI units may cr@p out because they are of poor quality, but not because anyone grounded the white wire to kill the spark.
 
Rumor or not the people that sell these kits are aware that there could be a problem with engine performance, even with the switch hook up as per there instructions. In my instructions for installing my thatsdax F50/47cc engine kit there's a Tip not to hook up the kill switch untill you have the motor running just the way you like it. To me this would mean to wait untill its broke in and running as smooth as possible. Then if you hook it up and your engine starts running like **** it should be pretty easy to trouble shoot the new problem as the switch. Without this Tip and you hooked up the switch as part of the initial install your engine would run like **** from the start and you would be pulling your hair out trying to fiqure out whats wrong. I"ve read several post on this site of that very problem and the top answer is to disconect the kill switch. Makes me think it mabe more than a rumor.
 
The problem is that they sell see fit to supply crummy switches!,which don't open up,thus disabling the ignition.If you get an HT engine,it's a good idea to just replace it,or at least check it out !
 
Back
Top