rev limiter

[unit412]

i was wondering if someone knows how to bypass a rev limiter on a 300ex, so i can check and see if it is bad. i would appriciate your advice on how to go about it.

[jordan_m6]

not sure if you can, due to the fact it controls your spark also

[pit/wood]

The rev. limiter is not a part,so to say,but a function of your cdi box. Did that help? as far as bypassing it,all you need to do is replace it with a performance rev.box. That lets is rev higher and most of them change the advance curve(when the plugs sparks in relation to the position of the piston,if you spark to late the fuel/air will not have time to combust completly.less power.the faster the rpms the more you need to advance the timing also) there is alot going on inside that little box.the system is real simple. if you want to know more just ask.

[JOEX]

The only two ways I know of to test the CDI is replace it with a one that is known to be in good working condition or test every other component in the ignition system. It's a process of elimination. I don't know why but the box itself can't be tested.

[tater_kamik]

the box could be tested, but it would be way too complicated. basically, you would have to give the cdi all the inputs it needs, and then test the outputs. it would have to get a simulation at different rpm's, voltage, etc, and every cdi is different. because the cdi doesnt cost anything and the cdi's for different quads are not interchangeable for the most part, it is not worth it to develop an cdi tester, and for shops to carry all of the different ones needed and to train personnel of the defferent ones

[wilkin250r]

Originally posted by JOEX
I don't know why but the box itself can't be tested.

It can't be tested because the operation of it depends on very specific inputs. In reality, it CAN be tested, if you have the right equipment. A simple multi-meter won't do it.

A multi-meter measures a voltage by sending that voltage through a known resistance, and measuring the current that results. Likewise, in order to measure resistance, it sends a known voltage and measures the current that results. That's it, that is all a multi-meter can do.

Your CDI requires a large voltage input from the exciter coil to charge up a capacitor, and then a small signal pulse from the pulse generator for timing to release all the energy stored in the capacitor, and send it to your ignition coil. Your multi-meter simply does not have the capability to reproduce these signals and measure the timing needed to test your CDI.

If I was really ambitious, I could put together the equipment needed to test a CDI. But, honestly, I'm not that ambitious. First off, it would cost thousands of dollars in equipment. Second, it would also be about $10,000 worth of engineering labor.

I like you guys, but not that much.

[tater_kamik]

as usual, we agree wilkins!

[bwamos]

Originally posted by unit412
i was wondering if someone knows how to bypass a rev limiter on a 300ex, so i can check and see if it is bad. i would appriciate your advice on how to go about it.

As the others said, really the only way you can test the CDI (within reason), is to swap it out with another one.

Aside from that:

What is happening with your motor? It is pretty rare that the 300ex CDI goes bad. I'm betting it is something much simpler.

Tell us what the ATV is doing, be as detialed as possible, and tell us what modifications to the drivetrain (pipe/filter/cam/etc.) you have made in the past year.