SU Carbs - I Can't Win

Tech tips and how to's

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Curtis
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Re: SU Carbs - I Can't Win

Post by Curtis » Sun Oct 21, 2018 11:30 am

spl310 wrote:
Sun Oct 21, 2018 8:04 am
What needles have you tried?
I have Keith's ADQ in there now.
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nismou20
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Re: SU Carbs - I Can't Win

Post by nismou20 » Sun Oct 21, 2018 7:56 pm

Curtis, Have you checked the float level? 2mm above or below the correct reference level could affect your mixture throughout the rpm range. I noticed my low end was like a switch on/off really jerky when accelerating. So, I checked the floats by attaching a clear aquarium hose to the bottom fuel supply connection and bending up against the chamber where I marked a float level to outside 23 mm below the bottom of float cover. My level was a bit high so adjusted the tab under the float and now it's a pretty smooth transition when accellerating. Idles better (leaner and cleaner) and power through out. Its part of base lining carbs and needle /jets are more for fine tuning.

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Curtis
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Re: SU Carbs - I Can't Win

Post by Curtis » Thu Feb 28, 2019 7:59 pm

So we had beautiful, cold sunshine today and I took the car out. While the car was still cool it ran good. When it got warm the problem started in.

On the advice of one of our local members I tried pulling the choke when it started to stumble and it ran better with the richer mix. I get the impression that once the carbs and the oil in pistons warmed up and thinned that's when it started. So I will move up to a heavier oil and richen the carbs a bit. Not sure I will get this done any time soon though since I have hand surgery Tuesday.
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Linda
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Re: SU Carbs - I Can't Win

Post by Linda » Thu Feb 28, 2019 8:23 pm

Curtis
I think the Magic Number setting can be adjusted slightly. Though tedious, I suggest taking the domes off, adjusting just a tiny bit one way or another. So if you are at.090, you could try .088 or .091 , whatever. But the idea is to keep the carbs even and measured, instead of the old “1/4 turn” which who knows what that is. Hopefully as dbrick stated, once you have them set you should not need to mess with them. Then checking floats, be sure both really totally float. New floats are really ideal, I think since too many brass ones are leaking or have gobs of solder weighing them down. Nice to have a matched set.
I never have done what Tom was suggesting. Will have to try that.
I believe Keith has mentioned adjusting the ADQ needles in or out a smidgen too.
Good luck!
Linda
Get well soon on the hand, don’t get anything in the incision line, you don’t want an infection.....
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