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Post by robg on Jun 5, 2016 13:12:15 GMT -5
I have a question concerning how to adjust my carburetor with a vacuum gauge. Is the "sweet spot" for adjusting the air/fuel mixture the point where the vacuum starts to drop as i am turning the mixture screw clockwise, or couterclockwise? Am i wanting the mixture to be slightly leaner than max vacuum reading, or slightly richer than max vacuum reading? I am assuning i should open the mixture screw to max vacuum, then close it slightly, but i am not sure.
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Post by Donny on Jun 6, 2016 17:14:03 GMT -5
Vacuum gauge is for creating equal draw on the intake of all cylinders to each other.
It really only matters on engines with multiple carbs, and really only effects idle and off idle acceleration.
A truly skilled tuner will usually have the cylinders a lil off from each other(while still holding reasonable idle) so that others come in during open throttle to aid acceleration.
To make things simple, back your idle off a bit. Adjust your mixture screws until fastest idle is achieved then back out 1/4 turn to ensure you are not too lean. If motor won't accept throttle at 1/4 out, adjust back in until it will. If you get plug fouling at idle keep touring the screws in wee bits at a time. Remember, the screws are not infinitely adjustable. All the adjustment from full open to full closed is in a out 1/4-1/2turn.
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Post by ScubaSteve on Jun 8, 2016 12:54:16 GMT -5
I have a question concerning how to adjust my carburetor with a vacuum gauge. Is the "sweet spot" for adjusting the air/fuel mixture the point where the vacuum starts to drop as i am turning the mixture screw clockwise, or couterclockwise? Am i wanting the mixture to be slightly leaner than max vacuum reading, or slightly richer than max vacuum reading? I am assuning i should open the mixture screw to max vacuum, then close it slightly, but i am not sure. I believe that the mixture screw you are talking about will only effect the idle, you should not have to adjust this. The A/F mixture is determined by the jets not the screws on the outside. The vacuum gauge will not measure the A/F mixture, it will only balance multiple carbs. I am not sure what the mixture screw on your carb should be set too but you should put it back to the stock setting, which is probably like 1-2 turns. do not crank the screw in too tight or you may damage the tip of the screw. I would have the carbs ultrasonically cleaned if you are having idle issues, if so, I have one question for you, have you changed the intake or exhaust?
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Post by Donny on Jun 20, 2016 21:12:22 GMT -5
How'd it work out?
Just another thing to throw at ya, if you can't lower the idle even with the idle stop all the way out, you have a vacuum leak somewhere. Happened to me today. Found a few loose screws on the carb allowing a wee bit of air to be sucked past a gasket. Took awhile to figure out. Only happened when really hot with cover on.
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Post by robg on Jun 21, 2016 9:32:23 GMT -5
My neighbour's son was home from his army deployment. He is was a marine mechanic before joining the army. He removed my carbourator, cleaned it and reassembled everything and set it up. . Took the boat out for a test run on Saturday evening and it ran like a charm.
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Post by Donny on Jun 21, 2016 11:18:05 GMT -5
My neighbour's son was home from his army deployment. He is was a marine mechanic before joining the army. He removed my carbourator, cleaned it and reassembled everything and set it up. . Took the boat out for a test run on Saturday evening and it ran like a charm. Fantastic. Hopefully you gained some experience in the process.
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