Spark Plug Appearance

[Taildraggerdave]

You can do a plug reading at any rpm but the 3 main ones are idle, mid rpm, and wide open. Run the bike for an extended period at any of these 3 points, pull in the clutch (if necessary) and kill the engine. Remove plugs and observe.

Take care,
Dave

 

[Jean-Pierre]

NGK Spark Plugs USA Here is a good link to read plugs, make a couple of hard runs , keep in mind with modern fuels it will be harder to read them, with a magnifier and a light you can view the insulator and also see the firing rings also called heat rings You will need to make your run at wide open throttle shifting thru all gears and shutting the bike down immediately after your test run to get an accurate reading

Thank you for the link, interessting

 

[btsom]

Another contributor to different mixture for one cylinder not yet mentioned is a leak in the flange where the intake bolts to the jug. I would only check the "lean" cylinder, as the one running rich wouldn't have much leaked air leaning the mixture. If you are still concerned, spray a small amount something flammable around the flange while the engine is idling and see if the idle changes. Some use WD40 for that but I wouldn't want to deal with the gooey residue, carb cleaner would work, but it has a tendency to spray with great vigor, and it can harm the paint. Perhaps others here will have a better suggestion.

 

[Jack Klarich]

Another contributor to different mixture for one cylinder not yet mentioned is a leak in the flange where the intake bolts to the jug. I would only check the "lean" cylinder, as the one running rich wouldn't have much leaked air leaning the mixture. If you are still concerned, spray a small amount something flammable around the flange while the engine is idling and see if the idle changes. Some use WD40 for that but I wouldn't want to deal with the gooey residue, carb cleaner would work, but it has a tendency to spray with great vigor, and it can harm the paint. Perhaps others here will have a better suggestion.

Try propane, if you have a leak it will suck in and speed up