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Discussion Starter · #1 ·
i bought an 04 660 that had a GYTR slip-on exhaust and K&N filter and stock jets. the thing backfired like mad and ran pretty hot so i ordered the vito jet kit for it. im running #25 pilot, needle on 3rd position, 150L/155R, 2 1/2 turns on air/fuel. it doesnt backfire as much now but i still get some on deceleration so i figured its still lean. when i pulled the plug its pretty black.... so is it running rich or lean?

also with this vito kit, it comes with new needles and clips, should i use those or the stock ones? i didnt think there was any difference in them so i kept the stock ones.
 

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You are running rich, you want a tan color. gray/white=lean and black=rich.
And I would use all the parts that came with the kit, it does matter your needle could be slightly worn sometimes hard to see.
 

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Discussion Starter · #3 ·
i adjusted the a/f screws in a bit to lean it up some, cleaned up the plug and took it for a ride up the road. when i checked the plug the center of the plug is brown but the area around the threads is black. is that normal or should the whole plug be one color? also now its backfiring more. :/
 

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i adjusted the a/f screws in a bit to lean it up some, cleaned up the plug and took it for a ride up the road. when i checked the plug the center of the plug is brown but the area around the threads is black. is that normal or should the whole plug be one color? also now its backfiring more. :/
When you screw the FUEL SCREWS in it leans your low end mixture, they are not Air screws, Change the needles, now it is up to to find where she is running rich, top end, mid range or low end, any of these can cause the plug to turn black.

Here is a scenario I just encountered with a buddies bike, we hooked up an 02 sensor, he was complaining of running to lean but his plug was black, 02 sensor says he was running very lean in the mid range, like 16 to 1 and top end was 9.5 to 1, so we raised the needles and leaned down the top end. and got his mixture right on, 12.5 to 1, bike runs perfect now, GET THE PICTURE.
 

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AmDD
Did you get that straightend out? You might also want to check the float levels. I had the say problems. Turned out when I did the clean tube test I was way high. Now it's alot better I just need to fine tune it now.
 

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Discussion Starter · #7 ·
yeah, i swapped the needles and ran it for awhile, checked the plug and it was still lean, so i played with the A/F screws and got it taken care of. i want to do the clear tube thing, maybe i'll do that tomorrow.


how do you tell where its lean/rich (top, mid, low end)?
 
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