How to read spark plugs

[velociraptor350]

If you have to rejet for mods you have done to your bike, your going to have to know how to read a spark plug. This site will show you how to do exactly that to tell if your too lean or too rich.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

The trick to doing a "plug chop" is simple. Install a fresh spark plug, and go do a WOT (wide open throttle) run through like 3-4 gears and then just kill the motor without letting off the gas. Coast to a stop, pull your plug and compare it to the chart above, it will let you know how to jet, either up or down. Always use a fresh plug on every run so you get the best possible reading.

 

[yamaharaptor350]

that sounds healthy for the bike lol

 

[velociraptor350]

Its better then running it too lean and frying your piston. :'(

 

[sparky3008]

Mechanics I have spoken to say you have to ride a bike for at least 30 minutes to get an accurate reading?

 

[velociraptor350]

Well the plug chop works with the different circuits, you always use a fresh plug, and do it at 1/4 throttle, 1/2-3/4 throttle, then WOT, you can tell if you need to fatter up the pilot, drop the clip, etc. by doing that. IDk about the 1/2 hour thing, i never heard of that. With simple mods you basically just need to fatten up the main jet.

 

[sparky3008]

I had questioned it too, why I asked, because that much time running wrong seems like it could do some damage.
Thanks

 

[lynxgen]

If you have to rejet for mods you have done to your bike, your going to have to know how to read a spark plug. This site will show you how to do exactly that to tell if your too lean or too rich.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

The trick to doing a "plug chop" is simple. Install a fresh spark plug, and go do a WOT (wide open throttle) run through like 3-4 gears and then just kill the motor without letting off the gas. Coast to a stop, pull your plug and compare it to the chart above, it will let you know how to jet, either up or down. Always use a fresh plug on every run so you get the best possible reading.

when I talked to the dealer here in town, thats exactly how they told me to check it. They didnt call it a "Plug Chop" but is exactly what they told me to do.

Find a field or somewhere, (Im thinkin a gravel backroad myself lol) and run it wide open. keep it pinned and hit the kill. dont let off the throttle, keep it pinned till it stops totaly."

just thought I'd through that in thier. I was wondering however about doing it at the different throttle positions.