yamaha 20 hp

[les mccauley]

could someone tell me what the function does the brass screw with the spring on it at the bottom of the carburettor or is only for draining fuel out of thanks les

 

[rodbolt]

Re: yamaha 20 hp

thats about its sole function. be aware that most had a tiny oring on the end.<br /> it may be the international market had a model run without a fixed highspeed jet.<br /> its possible its a fuel mixture but I have never seen a yammy with a high speed mix adjustment. but a lot of the older international stuff I dont ever see.<br />but the 96-97 US model of the twenty had no high speed mix and the fuel bowl screw was a drain.

 

[les mccauley]

Re: yamaha 20 hp

thanks kitty hawk i ran out of fuel , and i think ive lifted dirt etc the engine srarts ok put the revs on goes for about 30 seconds then losses power or stalls could it be lift pump or carb any ideas thanks les

 

[rodbolt]

Re: yamaha 20 hp

could be either one, usually you can pull that carb and clean it out and reassemble it without much problem unless the rubber bowl gasket swells.<br /> the lift pumps we just replace as a maint function, it could also be an airleak on the suction side of the pump to the liquid level in the tank, occasionally the quick connects on both sides of the fuel line go bad or the filter on the motor may be missing its gasket. sounds like for whatever reason the fuel bowl is running dry.<br />the lift pump is rebuildable if you wish but the parts cost almost as much as a new pump, or at least in the US. if you have a vacum guage you can install it at the suction side, vacum should be about 1-2"Hg. pressure on the outlet side should be 3-7 PSI.

 

[les mccauley]

Re: yamaha 20 hp

thanks kitti will give a go today les