Where to find carb needles ?

Saboat

Cadet
Joined
Sep 9, 2004
Messages
29
I have a 1972 40hp Johnson and have read on other threads on carb adjustments of the slow and fast needle settings.Problem is I cannot find anything that resembles a screw or needle on my carb except those that are for holding the bowl on :confused: .Where exactly should I look in case they are missing/broken ? Thanks
 

petrolhead

Chief Petty Officer
Joined
Oct 16, 2003
Messages
614
Re: Where to find carb needles ?

They are on the front face of the carb, you may only have one adjustable screw.
 

Saboat

Cadet
Joined
Sep 9, 2004
Messages
29
Re: Where to find carb needles ?

There is one adjustment that comes out the face of the carb and has an extention to a knob on the cowling marked fast - slow.Does this mean that each time you run WOT from idle(with knob in slow position)you would need to adjust this knob ? Or should I just set it somewhere in the middle ?
 

alcan

Commander
Joined
Dec 14, 2001
Messages
2,505
Re: Where to find carb needles ?

Saboat<br />That is your slow speed needle adjustment. You adjust it at idle only with the throtle fully closed. You motor has a fixed (non- adjustable high speed orifice.
 

BoatBuoy

Rear Admiral
Joined
May 29, 2004
Messages
4,856
Re: Where to find carb needles ?

Saboat, here is a quote of Joe Reeves on how to set low-speed jet.<br />"Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.<br /><br />Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.<br /><br />Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting. <br /><br />Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.<br /><br />When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway."
 
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