Which part of the plug do you inspect to determine the jetting? Insulator, electrode, or base ring? According to many different sites, they reccomend different locations. After adding my V&H slip on, I think i may be in a lean state. The bike runs very good all the way throughout the powerband but it has a popping noise upon deceleration around 6500 downto 5000 rpms. No overheating or drivability problems. I can't detect any flat spots because if I punch the throttle it accelerates without any hesitation. After revving the motor around 7000 grand for about 15 seconds, I took out and inspected the two outer plugs. The insulators were white with just a tad bit of brown near the electrode. The electrode looked grey in color and the base ring was black. What would that indicate?

EDIT: 1990 CBR600F
-K&N filter
-V&H SS2-R slip on
-unknown jetting, but previous owner said it was jetted.

 

You either read the electrode or insulator...not the base ring. I think it's the insulator. Either way it does sound like you're running lean. It should be a light brownish color.

 

Just check to see if you have the pipe sealed properly. A pop, (sometimes a backfire) when coming off the gas could also indicate air being sucked in from some where

 

Well I do know, that the mid pipe going onto the header does have a tiny little leak because I couldn't get the clamp to tighten it all the way. Also where the can slips onto the mid pipe, there is a leak but I figured it would leak there because the only thing holding the can onto the pipe are two springs.

 

also when is the best time to pull out a plug to check its color??

 

Ideally you should pull it immediately after full throttle. For the drag strip guys do this: right as you go through the lights, kill the engine before you let off the throttle...don't let it idle or run part throttle at all as this will mess up your reading. I don't think free revving it will do the same as there's no load. So ideally, you should find a straight, run at high rpm for a few seconds (or more) and then immediately kill the engine, pull the plugs and take a look. Now this isn't really convenient to do on a bike as the plugs can be harder to get to. But if you're doing anything else you're not getting an accurate reading. Most people just get the O2 sniffed while on the dyno...much easier and more accurate than plug reading.

 

If the bike is carb i would go stright to the carbs and jet them. Your running to lean. If your injected you need a power comander. Trust me

Uh Huh

 

check this page to figure out how your plugs are doing....

http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html

 

Generally, the ceramic part of the plug, (what starts as originally white) is what to look for.

Light tan color means everything is running tip-top.

A dark dark brown, and oily residue means you are running too rich. Too much gas, not enough air.

A whitish, sometimes clumpy residue all over the tip and ceramic of the plug, (like someone put white caulk all over the plug) means too lean, and your bike is running too hot as well.

 

Well today I put inwent from 98 to 114mains. Needles are at 4th groove from top. It seems like nothing really changed. It is still popping at 6500 rpms? Do needles spray any gas at WOT cause I was thinking of lowering the needles to see if that makes my WOT more snappier.

Dynojet Stage 1 Kit: needles at 3rd clip, 98-102 MJ
Dynojet Stage 2 Kit: needles at 4th clip, 120-124 MJ

My mods are K&N filter and V&H slip on. And how long does it take for a plug to change color?