jetting and reading the plug

[jonooffler]

I hope this one will be a short thread this time.I have been having issues with a low rev stutter on a 2003 KDX220 (UK ) bike having changed the pilot jet several times 42 -38 now on a 35 the stutter feels much better I have just taken the plug out after a good ride and the plug is a nice clean and dry light brown the only worry is a a white halo about .005" around the edge of the sharp edge on the spark tip.
Any views on this.
Just to add the UK pilot jet should be 38.
Thanks Jono

 

[whenfoxforks-ruled]

Where is the colored mark at on the ground strap? http://www.dragstuff.com/techarticles/how-to-read-plugs.html

 

[helio lucas]

fox, better yet... :cool:
http://www.dirtrider.net/forums3/showthread.php?t=89861&highlight=tom+turner

 

[jonooffler]

Hi the earth strap looks a light brown and very dry ?It's justa very thin white line around the edge of the electrode tip.
Jono

 

[helio lucas]

you have to observe the whole plug. click my link, scroll down to the image of the plug.
do a wide open plug chop on a new spark plug(quickly kill the engine, not coast down with the engine working) and see for yourself. then tell us what you think.
me think too hot or too cold of a plug.

 

[mudpack]

Plug chops will tell you little about the pilot jet: chops are all about main jets.
The way it runs at very small throttle openings will reveal much more about the correctness of the pilot jet than a plug reading will.

Mud

 

[_JOE_]

Mud is right. Where is airscrew set at?

Have you altered the air box at all?

 

[whenfoxforks-ruled]

I set the air screw, seat of pants on the rest. Check the plug after each ride. A plug chop is just for reading the burn ring in the top of the porcelain, thats it. You can feel the main when its right, and the same with the rest, it pulls the hardest. Lean pulls weak, and rich just flounders. Generally, the plug will tell you also, wet or dry? You will never jet a bike with a mechanical issue somewhere, denial does not work either. Overdue for a rebuild, a half arsed rebuild, polishing and other garage brewed mods, timing and the list goes on, and you will never be able to jet it. If you make changes more than 3 sizes, or it seems to make no difference/puzzling, its not the jetting. Start with everything within spec, keep accurate notes and time on the engine hours.