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Post by Deleted on Jun 21, 2013 11:50:21 GMT -5
My plug is slightly brown on the center porcelin and the flat bottom ring pf the plug thread seat is black. Scoot running great and all that but believe its a tad bit richer than we'd like it. The AF screw is adjusted for best idle etc but would turning the screw in a bit lean it out some throughout the whole throttle band? Heres my issue...75 jet too lean  a tad bit rich. I have an 82 i can try but trying not to yank it off again since it running so much better than the 75 did. |
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Post by lykos23 on Jun 21, 2013 13:52:19 GMT -5
Too rich isn't harmful to the scooter unless you're waaay off. Sounds like you're OK. You're more than welcome to try that 82 jet though, it may help with fuel consumption.
The A/F screw only effects the idle and up to 1/8 throttle.
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Post by jerseyboy on Jun 21, 2013 14:01:42 GMT -5
Does it have a free flow filter and exhaust?
BTW-Hows the other bike running that was making all that valve noise???
Tom
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Post by prodigit on Jun 21, 2013 14:18:49 GMT -5
The AF screw does very little to riding at half open throttle to full open throttle.
The amount of fuel it lets through is minimal. It mainly makes a difference on idle.
You could adjust it (turn it in) for a lower fuel consumption, but make sure it still idles fine. I'd say, screw it in, until the bike starts acting up, then screw it back for 1/4 turn. reason being is when weather changes, sometimes, if you set it at it's limit, what works in one weather may not work in another weather.
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Post by earlwb on Jun 21, 2013 14:49:46 GMT -5
The AF mixture screw adjusts the low speed mixture. To adjust the mid range through high speed mixture you need to change the needle profile or the main jet in the carburetor. Most carbs are the CV type (constant velocity) and have a piston connected to a diaphragm, as the engine speed increases the piston moves up opening up the intake more,. There is a tapered needle in the center of the piston that moves up and down in and out of the special orifice there. The main jet actually sits below the orifice and controls the maximum amount of fuel that flows into the engine. The needle serves as a metering device for it.
Now if you are a little on the rich side and want it to me more lean, you could go with a more free flowing air filter intake setup. Othewise one changes the main jet out as needed. Normally the engines are set quite lean from the factory, too lean for my preferences, so much on the thin red line that anything that lets the engine breathe a little better results in it being suddenly too lean.
So in my opinion based on your comments I would say your engine is setup pretty good actually. It likely isn't anything to worry about.
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Post by jerseyboy on Jun 21, 2013 17:22:11 GMT -5
[replyingto=earlwb]earlwb[/replyingto]Funny you say that,,
Cause as soon as I put on a free flowing air filter on my stock 150,,it did not even want to run from mid to top,,it was so lean with a 102 jet,,i have a 118 in there now,,prolly too much but Im waiting to see a little carbon build up in my muffler,,so far its clean and mean...lol
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a tad bit rich. I have an 82 i can try but trying not to yank it off again since it running so much better than the 75 did. 
Main Jet
