Topic: Plug reading

[550Resto]

Hey all, not 100% on reading plugs and was hoping someone could she some light on it for me. I've attached a picture of the number 1 cylinder plug. 78 550k, delkevic 4into1 exhaust, stock airbox. Thanks!

[CB650CPastor]

Was this a plug chop? Looks pretty lean unless the picture is washed out from a flash. I don't see any color on the insulator at all. Insulator should be brownish/tan. Take a picture in good light without the flash.

[550Resto]

No plug chop. Here are 2 without flash. What are the consequences of running too lean or too rich?

[mrfish2]

Too lean will overheat the engine, causing it to ping. Too rich burns a lot more gas and causes stumbling. Have you read through the Carb FAQ?

[flybox1]

plug readings mean nothing unless they are for ONE, constant throttle position, and you didnt list anything.
we cant help unless you do a proper chop and list the throttle position.

[brewsky]

What gap are you using?

[flybox1]

What gap are you using?

good catch 

[grcamna2]

A little rich won't be bad but too lean is not good.When you check the plug color make sure to look down deep into the center porcelain to see some color,even w/ sunlight shining directly into it.What main jet are you running now ?

[550Resto]

Spark plug gap is per the manual, between .02 and .03 inches. Mains are stock. It had 100 mains in it, but harisuluv swapped them out to stock size...92 or 90 I believe.

[brewsky]

Spark plug gap is per the manual, between .02 and .03 inches.   

If so, my eyes are really BAD!

.02 mm maybe?

[grcamna2]

Spark plug gap is per the manual, between .02 and .03 inches.   

If so, my eyes are really BAD!

.02 mm maybe?

.028in. would be ok

[flybox1]

the picture above shows what looks like noticeably small plug gap on one plug
the other photo is too blurry to tell

[550Resto]

Manual calls out 06-07mm  or .024-.028 inches. I set them all at .026 inches with a plug gapper.

[550Resto]

Yeah somehow the gap on that one was way smaller even though I had set them all the same. Re gapped it.

[grcamna2]

the picture above shows what looks like noticeably small plug gap on one plug
the other photo is too blurry to tell

Definitely a problem 

[550Resto]

If running too lean how does one richen the mix? I have searched the forums some and I've read that there are adjustment screws on the side of the carbs, but I'm not seeing any. All I see are the IMS on the bottom of the carbs. These are pd46c carbs. Most stuff I see is in regards to the 46a's

[flybox1]

If running too lean how does one richen the mix? I have searched the forums some and I've read that there are adjustment screws on the side of the carbs, but I'm not seeing any. All I see are the IMS on the bottom of the carbs. These are pd46c carbs. Most stuff I see is in regards to the 46a's

do you know what the IMS does?

[550Resto]

From what I've read the idle mixture screws can control either air or fuel depending on the model of carbs. Not sure about the 78 style carbs, but I imagine it would control fuel. If that's the case turning clockwise would richen and counter would lean it out, correct?

[jonda500]

From what I've read the idle mixture screws can control either air or fuel depending on the model of carbs. Not sure about the 78 style carbs, but I imagine it would control fuel. If that's the case turning clockwise would richen and counter would lean it out, correct?

No, that would be the older air screws. Your IMS's will make it leaner by screwing them in, richer by screwing them out,
John