1979 Evindrude 70 HP - Carb Issues (needle valve, idle and off-idle jets)

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Jun 27, 2009
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I completely rebuilt the powerhead on a 1979 70 Hp Evinrude (70973R) and have been having problems with the carburetion since the rebuild. It starts and idles fine, but when I attempt to open up the throttle it either dies or boggs really hard. When I rebuilt the carbs the first time I did not install the springs on the needle valves becuase there were no springs on the valves that were in the motor. After reading this thread, I am going to go back and install these springs and see if that helps.

I also think I may have mixed up the idle and off-idle jets. They are the same thread size but different orifice sizes. The idle is a #57 orifice and the off-idle is a #35. Does this imply that the idle jet has the larger orifice?

Also - the rebuild kit says to back off the off-idle jet by one turn, but these are just fixed orifices, not adjustable jets. Do I really have to turn the off-idle jet out one turn?
 

Daviet

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Re: 1979 Evindrude 70 HP - Carb Issues (needle valve, idle and off-idle jets)

According to the parts breakdown you do not have an adjustable low speed jet, nothing to adjust. The # 35 jet is the one that goes in the top of carb, low speed, install both jets so that they are tight. Do you have a factory manual for your engine, a good investment if you don't have one.
 
Joined
Jun 27, 2009
Messages
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Re: 1979 Evindrude 70 HP - Carb Issues (needle valve, idle and off-idle jets)

Yes, I have the factory service manual - there is no way I would have been able to rebuild the powerhead without it.

Yes, I know that the #35 is the off-idle jet, I just don't know which one it is since I mixed them up. Is #35 the smaller or larger orifice diameter?
 

Daviet

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Re: 1979 Evindrude 70 HP - Carb Issues (needle valve, idle and off-idle jets)

Arn't the jets marked with a number on them?
 
Joined
Jun 27, 2009
Messages
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Re: 1979 Evindrude 70 HP - Carb Issues (needle valve, idle and off-idle jets)

I am not sure if they are marked or not - I will check that when I pull them apart again tomorrow night.
 
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