im thinking about getting on of these, do they hurt the reliability and ease of starting on a 400ex? how bout power? keep in mind i already have the 440 kit and stage 2 hotcam

 

it will make alittle more heat but won't hurt anything. my EX starts easier since I put my key in. the key does not add power. it just makes what you have work better. my ex is stock with the sparks key and the key just adds more snap to the trottle. I like it and would do it again for 15 bucks.

 

I was checking these out also. I remember reading somewhere on the website that they are designed for stock and should not be used on bored out quads. I guess the heat created is a big factor. You might want to contact sparks and ask them.

 

they are not recommended for built motors as they will create more heat.