Fine Tunning yamaha breeze carb
 

Hello All,

I am fine tunning a clean carb that is running lean. I adjusted the needle valve all the way down on the clip for a short stroke but plug shows light gray/ lean condition. I went with pilot 15 / main 85 ( one higher) and still had to adjust the needle valve all the way down after trying it in center position after jet change. I am seeing improvements in response and power but am I getting unmetered air / valve issue or do I go to a larger jet and try again.

2000 breeze bought used last year.

CR7HSA Plug. No pictures before jet upgrade from 82.5 to current 85 for main and 12.5 to 15 for pilot.

Plug is darker by 1/2 shade than the picture butshould it be a little darker? Starts and runs fine with a slight hesitation from off throttle to 1/8th but then power seems to be smooth through upper rpms

http://s306.photobucket.com/user/chu...tml?sort=6&o=0

http://s306.photobucket.com/user/chu...70079223590408
Chuck

What are the factory jet sizes? You shouldn't have to go up on jet sizes unless you did some modifications to the air filter or airbox. If everything is stock, then you have issues somewhere else. It could be sucking too much air from somewhere causing it to lean out, like a split carb boot or a leaking gasket.

Thanks for the feedback,

The air filter looks like a purple K & N in the airbox and nothing seems to be bad with boots/ seals. I assume the K & N filter will allow for more airflow so a standard jet of 82.5 should be changed maybe 2 sizes up with an airbox modification. I am getting richer results but I have no adjustment left on my needle valve with an 85 jet. I am using a pilot jet of 15 and do have a little stumble hesitation so I assume a 17.5 pilot jet can be tried along with a 87.5 main.

Whats your opinion on the pics/ burn color. My pilot screw is out 2 3/4 - 3 where it runs best


Thanks for the feedback

Chuck, Atl GA

I turned the air screw in for 2 turns, The idle drops and seems a little sluggish on under 1/8th throttle and seems to be ok to WOT but burning a little richer but still is not right. its 100% rideable but its not as good as it can be.

20131106_100642_zps1f39eca0.jpg Photo by chuckneste | Photobucket

Looks like you're on the right track, the 1st pics of the plug looked too white for sure. You could probably go up 1 more jet size on each the pilot and the main. Sounds like you're close on the main but still lean on the pilot. I've always read that you keep going up on the main until it starts sputtering, and then go down 1 size.

Thanks Raptor,

I have a honda ex300 that took a month to fine tune. I am going to be away for a few weeks but will post my results after rejetting the carb. I am close but dont have any adjustment left. its good now but can be better