.46 AX stops running at 1/2 throttle

I have a OS .46 AX that I just picked up used from a guy , runs at idle fine ... When I get up to 1/2 throttle it just shuts off . I have tried to move the needle out , 2 turns , 2 1/2 , 3 and 3 1/2 ....... still no luck ..

Any idea's ?

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.46 AX stops running at 1/2 throttle

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Mar 15, 2010
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And the low speed needle?
by: Michael from Oz

G'day. Your 46 AX has a fuel metering carby with a two needle setup. The main needle governs the total amount of fuel available and controls the mixture at the top end of the rev range. The low speed needle (which is accessed via a small screw slot in the main body of the carby) controls the mixture from idle to about 80% of the throttle range.

It sounds to me as if someone has been trying to adjust the low speed needle and got it very wrong.

New engines (although not OS usually) have their low speed needle set pretty rich to make sure the engine is not run lean initially. You need to find the factory setting for your low speed needle. A simple way to get things close to right is to fit a small piece of tubing on to the fuel inlet, set the carby where it would be for idling (usually with the barrel open about 1/32 inch or the thickness of a pin) then blow through the tube. If you can blow, close the low speed needle until you just can't blow then open it until you can just blow some air through. If when you blow, close it until you cannot blow then open it until you can just blow through. This is a good starting point. Not perfect but not miles wrong.
Then adjust the top end to absolute maximum revs and then adjust the bottom end and keep going between them until you are happy with the bottom end. Finally make the engine top end slightly (300 to 500rpm lower) rich.

Does this help?

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Mar 15, 2010
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Submitted by: Michael from Oz

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G'day. Your 46 AX has a fuel metering carby with a two needle setup. The main needle governs the total amount of fuel available and controls the mixture at the top end of the rev range. The low speed needle (which is accessed via a small screw slot in the main body of the carby) controls the mixture from idle to about 80% of the throttle range. It sounds to me as if someone has been trying to adjust the low speed needle and got it very wrong. New engines (although not OS usually) have their low speed needle set pretty rich to make sure the engine is not run lean initially. You need to find the factory setting for your low speed needle. A simple way to get things close to right is to fit a small piece of tubing on to the fuel inlet, set the carby where it would be for idling (usually with the barrel open about 1/32 inch or the thickness of a pin) then blow through the tube. If you can blow, close the low speed needle until you just can't blow then open it until you can just blow some air through. If when you blow, close it until you cannot blow then open it until you can just blow through. This is a good starting point. Not perfect but not miles wrong. Then adjust the top end to absolute maximum revs and then adjust the bottom end and keep going between them until you are happy with the bottom end. Finally make the engine top end slightly (300 to 500rpm lower) rich. Does this help?

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Mar 13, 2010
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.46 AX stops running at 1/2 throttle
by: Anonymous

make sure there no dirt blocking the jets take needle out and inner tube and blow backwards
check the nipple on muffler make sure thats not block so tank not getting pressure