Before I adjusted my air/fuel mixture screws, I was getting in the lower 40's for mileage but it seemed to need the choke on longer when starting cold and it back fired a bit upon decelarting. I blamed the backfiring on the aftemarket 4 into 1 exhaust. I adjusted the fuel mixture screws using the highest RPM method and it seems to start easier with less choke and the backfiring has decreased significanlty. But now my mileage is in the upper 30's. Is this typical when adjusting the air/fuel mixture screws? Dies it mean I'm running to lean?
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Could also be running a bit too rich. How does the exhaust smell after the bike is fully warmed up?
If it smells rich, you might try turning the screws clockwise about 1/8 turn.
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mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
#1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
#2 son: 1980 GS1000G
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Siblings and Spouses
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Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
(Click on my username in the upper-left corner for e-mail info.) -
Your right. That would be more of a rich condition. I will try turning the screws clockwise (in?) about an 1/8 turn and see if that makes a difference. I haven't smelled anything different from the exhaust but then I really haven't inspected it yet. I will take a sniff when I get home from work today.Comment
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There is an ideal mixture (called stoichiometric) where you will get the most power and best mileage. Any deviation from that, either richer or leaner, will result in lower mileage. The trick is to determine which side of the peak you are on and adjust accordingly. If you find that leaning it 1/8 turn makes it worse, go rich by 1/4 turn (to erase the 1/8 you just did and go 1/8 more) to see how that does.
If you are looking for highest mileage, you will be tweaking a bit longer than those who adjust until it's better than it was, but don't bother to look for more.
.sigpic
mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
#1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
#2 son: 1980 GS1000G
Family Portrait
Siblings and Spouses
Mom's first ride
Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
(Click on my username in the upper-left corner for e-mail info.)Comment
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I adjusted the air/fuel mixture screws so that all four were turned 1.75 turns out. That lowered the idle a bit and caused a little backfiring again upon decelarating and a little bit longer warmup on a cold start but now my mileage is back in the lower 40's again. I always thought the highest idle adjustment was best but I guess not.Comment
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Plugs?
What do your plugs look like??1980 GS1100E....Number 15!
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Unless you drive around at idle speeds the mixture shouldn't effect gas milege.Comment
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Before I adjusted them the first time the plugs looked perfect. A light tannish color. I haven't checked them again though. I'll take a look at them again when I get home from work. So the air/fuel mixture screws only affect the idle?Comment
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