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Question about HS4 Tuning

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kbjohns Avatar
kbjohns Ken Johnsen
Staten Island, NY, USA   USA
I've rebuilt and installed HS-4s on my 71 B. Set the idle according to the procedures suggested in the forums library. When I go to adjust the mixture, on the front carb I get a slight increase and then return to normal idle when I lift the piston about 1/6th of an inch. When I do the same with the rear carb the engine wants to stall. Both leaning and enriching the mixture leads to the same result. I've never done this before and am looking for some guidance as to what I'm missing. Overall have had the car out for a run and the throttle response is great, much more sensitive and more pick up the Weber DGV

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ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
Did you follow the carb balancing procedure? If you've not done this before a sync tool can be helpful, once familiar with the sound it can be done by ear.

Also, are you SURE the float level is the same on both carbs? Easy check is to remove the dashpots, pull the choke and see where the fuel level is. You may have to puff into the jet to get the fuel to bounce.

kbjohns Avatar
kbjohns Ken Johnsen
Staten Island, NY, USA   USA
I did balance them with a Unisyn and did follow the procedure for adjusting the fuel mixture. I did not check the float level -thanks I will do that this afternoon

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dipstick Avatar
dipstick Kenny Snyder
La Center, Washington, USA   USA
1941 Ford N-Series
1958 MG MGA 1500 Coupe "Rosie"
1970 MG MGB GT "Pat's GT"
1971 MG MGB "Gifted To Me"    & more
With the dashpots and pistons off, the ignition/fuel pump on, look down into the jets to determine the fuel level. Maybe 3/8" down from the top of the brass jet. The top of the brass jet about .060" down from the bridge. The linkage between the carbs may have to be loosened to equally sync them.

I too have a silver 944.cool smiley



Be safe out there.
Kenny


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the omega man Avatar
the omega man phil wilkins
staffordshire, Stafford, UK   GBR
When you are happy with how it runs, I would drive to a garage which has an exhaust gas analyser. Ask them to give you a print out of the readings. This is best way to confirm mixture is fine tuned to almost perfection.

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