KX Riders

Maintenance & Technical => KX500 Original => Topic started by: jdb1989 on September 29, 2009, 08:53:52 AM

Title: how far a gap should my plug jump
Post by: jdb1989 on September 29, 2009, 08:53:52 AM

cause it jumps short i have to touch it to the frame to get it to jump

Title: Re: how far a gap should my plug jump
Post by: 95formula847 on September 29, 2009, 09:08:13 AM

+1 on this. im also interested

Title: Re: how far a gap should my plug jump
Post by: KXcam22 on October 01, 2009, 05:03:15 PM

I am not 100% sure what you are looking for.  A plug has to be grounded to the frame or engine for the spark to jump.  The coil usually delivers 20,000 to 40,000 volts to the plug.  With a screwdriver jammed in the plug cap I have seen the spark jump an inch or more to the frame.  On my sons XR200 I was kicking it over (flooded) to clear excess gas out of the cylinder. Spark jumped out of the empty cap to the frame (at least 2") and ignited the gas. Exciting!  The KX500 should show you a lively spark at the plug.  Sometimes it helps to turn out the lights to see it easier. Cam.

Title: Re: how far a gap should my plug jump
Post by: jfabmotorsports.com on October 01, 2009, 05:06:25 PM

An instructor in high school electronic class told us that a good rule of thumb was 1/4 inch per 10,000 volts. That conferms Cams findings...+ or-  :wink:

Title: Re: how far a gap should my plug jump
Post by: azracer19 on October 02, 2009, 05:48:29 AM

You could always use the idiot technique.... ya i have been that idiot.. grab the plug gently kick the bike if your eart skips a beat  your good... its also a good way to get a girlfriend out of the house just have her hold the plug and see how far the jumps and then runs to her car

Title: Re: how far a gap should my plug jump
Post by: KXcam22 on October 02, 2009, 08:12:32 AM

The idiot technique in action:  Kind of off topic, but once when I was riding my bike in the winter (studs) I ran into a large group gathered around a snowmobile, trying to get it running.  They were checking for spark with the plugs (2) removed, one guy standing on each side of the hood bent over holding the plug (but not against the cylinder-the dummies). I arrived just as the owner had carefully explained to the crowd not to drop the plugs as they might hit something, crack and he didn't have a spare.   Now picture this with time slowed down!  The owner starts pulling the pull-start like he is going to win a medal.  The two guys holding the plugs catch the full 40,000 volts from the first pull, throw the plugs and start yelling and dancing around in the snow.  Just in time for the 2nd pull two bystanders leap in and catch the falling plugs and then get the full 40,000 volts from the 2nd pull.  Then there was 4 guys yelling and dancing aroung in the snow.  I had to ride away I was laughing so hard.  It still rates as one of the funniest things I have seen. Cam.