tan/gray plug and still bogging?

[400exstud]

Yesterday I went to go and change my main jet from a 160 to a 155 because it was bogging and felt really lame and when I did this I also changed the plug. The plug was a tan/gray color but the quad was still bogging down. This seems weird so I went out and beat the piss out of the quad with the 155 main in it and it flys now. 100% improvement over before.

Does this seem weird to anyone else?

[Pappy]

usually when you rejet from a rich condition you will notice better throttle response and more power:p

the tan and brown color indictaes very little, unless you were doing plug chops. with your set up, a 152 would be about right IMO with an aftermarket filter and closed airbox, the 155 should be good if the lid if off.

[h400exrydr]

well that is weird... i have a 155 wit the mods in my sig and it is running realy really rich, like it wil b idleing and all of a sudden the idle will slow down and i will go to give it a little touch of the throttle and itll bog but then still run and then ill do it again and itll rev up good. really comfunsing. i have a 42 pilot jet too. can anyone help me out?? and my plug was really really black.

[zeppelin]

Originally posted by 400exstud
Yesterday I went to go and change my main jet from a 160 to a 155 because it was bogging and felt really lame and when I did this I also changed the plug. The plug was a tan/gray color but the quad was still bogging down. This seems weird so I went out and beat the piss out of the quad with the 155 main in it and it flys now. 100% improvement over before.

Does this seem weird to anyone else?

try cleaning your airfilter

[400exstud]

the tan and brown color indictaes very little, unless you were doing plug chops. with your set up, a 152 would be about right IMO with an aftermarket filter and closed airbox, the 155 should be good if the lid if off.

That makes me feel better!:D

[400exstud]

well that is weird... i have a 155 wit the mods in my sig and it is running realy really rich, like it wil b idleing and all of a sudden the idle will slow down and i will go to give it a little touch of the throttle and itll bog but then still run and then ill do it again and itll rev up good. really comfunsing. i have a 42 pilot jet too. can anyone help me out?? and my plug was really really black.

Anything that has to do with idle is the pilot jet.

[bwamos]

Aye.. loading up at idle won't have anything to do with the main jet.

Idle circuit (pilot & air screw) for idle => 25% throttle

Needle & Needle Jet for 25% => 75% throttle

Main Jet for 75% => full throttle.

[400exstud]

Do you guys really think that my engine is safe? That plug was pretty white even before I took it down two steps (160 -> 155). It does ride very good though, no bogging or backfireing.

I bet it will be white as snow now:p

[bwamos]

You may be lean in the mid throttle range if it's grey. It's not always your main jet causing the problem.

Raise your needle a spot (clip down), and see if it gets better.

[400exstud]

I might have to try that again. I adjusted the needle when the main jet was really rich so then I moved it back. This fat setting on the needle didn't compliment my overly rich main jet so it worked that the time. Now that I have the main closer I may have to change that again.

I am also going to back the the air/fuel screw out 1/2 turn because it is poping a little when it I chop the throttle from wide open.

[James Cornell]

i have a 97 300ex with a 400ex carb 145 main jet and have tried 38,42,45 pilot jets all resulting in a lean condition, i put a new plug in it and you cant even tell the plug has burned any fuel, 1/2 and wo throttle is great with a great plug color, any ideas?

[bwamos]

You're probably turning your air screw out too far. The keihins have an air screw not fuel screw. Turning them out makes it leaner. Turn it all the way in to seat, then back it out one turn. See how it does there, then adjsut.

[James Cornell]

ok thanks, i misunderstood the manual, i'll give that a try and hope like heck it fixes my problem.