Colortune diag question

I stuck my new colortune plug into Cylinder 1 today, just to have a look and see how it works. My bike (or that cylinder, anyway) is running a little bit lean, but it's a light blue not a white, so it's okay for now.

The firing seemed really arhythmical, though. It seemed to fire in short bursts, not very steadily. This doesn't seem normal to me; seems like it could be misfiring. Could it be a gunky carb not getting a good mixture in every time? Or bad ignition coils? Or does the firing pattern actually look kind of random?

Another question, that I'm sure I'll figure out but I'll might as well ask: what's the proper petcock setting for removing the gas tank hoses and attaching a longer hose? Seems like if I leave it on "Run", gas will pour out when I pull the hoses.

Carlos

 

Colortune don't know , gas tap , leave on run as fuel should only come outta there when the motor is running [vacuum operated]..

 

An arythmic reading is indicative of a lean pilot mixture screw setting where the cylinder isn't getting enough fuel everytime or a plug wire, cap, sparkplug or coil that is shorting out. Turn the mixture screw out while viewing the colortune 1/2 turn. Blip the throttle, the flame will go yellow and then see if it returns blue and constant.

 

Blue's right - the carb is running lean enough that it's missing sometimes - pretty common for our bikes. Richen that puppy up just a tad.

 

Thanks for the tips.

I'll crack those carbs open (for my first time) this weekend and have a go at it.

 

I would make sure the plugs are good before tearing into the carbs. But if you do have to go into them go here and study first.
http://www.slygrin.net/xj750/html/body_carbs.html