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Carb tuning question

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Does anyone actually check the color of the spark plug to see if they are running lean/rich? I am thinking I am a little lean due to lack of top end and some hesitation at high rpms (constant throttle).

Do you think to go down a clip and increase the Main Jet?

will it hurt anything to try this?

thanks for any help.

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Spark plugs are very hard to read with modern fuels. If you are a race tuner using race gas and controlled conditions and 20 yr experience, then OK. But not for the average guy.

Post your motorcycle, current jetting, and operating conditions

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My current configuration is 3x3, DJ with 142.5/25, 3 turns out on screw. Yosh RS3 with TEC IN. Athena Big Bore 94mm 12.3 compression piston. Hotcam stage 1 intake and exhaust. Bike starts and idles good. Currently at sea level and hot here in florida.

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brown = good

black/oily/whit = bad

if it's burning at the proper temp, it'll be a dark tan/brown color. if it's running really rich it'll be a mucky black color. if it's white, its running too hot.

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brown = good

black/oily/whit = bad

if it's burning at the proper temp, it'll be a dark tan/brown color. if it's running really rich it'll be a mucky black color. if it's white, its running too hot.

sorry,but no.

with modern fuels the plug will look like new when the jetting is correct.

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I need to get out with the cover off. Will do shortly and let you know.

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Ok took cover off per eddie's direction and I thought it pull harder to limiter. I could still get some hesitation from it but I thought it was better with the cover OFF.

Should I try to go the other direction with reducing my 3x3 hole to see what it does?

thanks for the help

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Covered about 1/3 to 1/2 with tape and the hesitation is gone. I think there is a little more top end too. Got to 87 indicated. So I need to go down one on the Main Jet. Currently set to 142.5 I am guessing 140? or 138?

I take that back. Looks like I need more fuel because I taped off some of the air? So looks like I need 145?

thanks,

matt

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Im having a similar problem, Ill be at 75mph and pull the throttle wide open and my bike starts to buck/hesitate for a second or two and goes back to normal, then occasionally hesitates while holding it down at about 85-90mph

08 DRZ400s

Full Yoshimura RS2

3x3 mod

DynoJet:

155 main

25 pilot

4th clip on needle

mixture screw 2.75 turns out.

500-1000ft above sea level, 60-80 degrees

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