How to adjust Hitachi Carb?

[Draynor]

I have a 71 510 goon with the factory carb.

 

After screwing the air/fuel mixture screw all the way in how many turns do you turn it out?

 

And any other carb tuning info would help Thanks

[dobo]

Best way to tune carbies is by ear. Get the engine to warm temp and fidle with the adjustment screws til its running good. Theres no hard and fast rule.

[datzenmike]

There's no set amount. What I do is warm up thoroughly and turn the idle down or set a nice idle speed by ear. Turn the idle mixture screw in until the idle quality drops off and it starts to stumble. Now turn it out until you get the fastest smooth idle speed. Turn the idle speed down to 650-750 Now repeat but turning in until the idle quality drops, then out until the idle quality drops. Usually about 3-4 turns. Pick a spot roughly in the middle between these two points. Idle speed and quality may improve again from the first try, so turn the idle speed down and repeat the in and out and setting in the middle. Keep going untill you cannot improve the idle speed and quality. You're done.

 

Before setting the idle mixture always check and set both the timing and the valve lash. You can set the mixture in order to get the motor running to set the timing and valves but always go back and re-adjust the carb. Improper timing and valve lash can make a big difference in idle quality.

[Draynor]

There's no set amount. What I do is warm up thoroughly and turn the idle down or set a nice idle speed by ear. Turn the idle mixture screw in until the idle quality drops off and it starts to stumble. Now turn it out until you get the fastest smooth idle speed. Turn the idle speed down to 650-750 Now repeat but turning in until the idle quality drops, then out until the idle quality drops. Usually about 3-4 turns. Pick a spot roughly in the middle between these two points. Idle speed and quality may improve again from the first try, so turn the idle speed down and repeat the in and out and setting in the middle. Keep going untill you cannot improve the idle speed and quality. You're done.

 

Before setting the idle mixture always check and set both the timing and the valve lash. You can set the mixture in order to get the motor running to set the timing and valves but always go back and re-adjust the carb. Improper timing and valve lash can make a big difference in idle quality.

Thanks for the info! I am gonna go out there and try it now. I have already done the timing...

[ggzilla]

Mike's method is what Nissan recommended, except they have a suggested RPM speed (usually 650 to 750 RPM, depending on year) and ... they suggest when you find the "best" idle (as Mike does), then turn it in untill the speed drops 25 RPM. This is called "best lean idle" and will improve emissions and fuel economy at idle.

 

Turning the screws a set amount is a rebuild setting which should be enough to get the engine started. After that you must adjust it for real.

[Draynor]

Mike's method is what Nissan recommended, except they have a suggested RPM speed (usually 650 to 750 RPM, depending on year) and ... they suggest when you find the "best" idle (as Mike does), then turn it in untill the speed drops 25 RPM. This is called "best lean idle" and will improve emissions and fuel economy at idle.

 

Turning the screws a set amount is a rebuild setting which should be enough to get the engine started. After that you must adjust it for real.

Thanks man! I pretty much got it where I want. it starts up much nicer and idles better after the timing and adjusting the carb.

[Datsun fan]

If all stock and timing,plugs, valve lash bla bla bla then my experience suggest 2.5 turns for very good economy and 3.5 for balanced economy/power.

Use this info to be sure that your valve lash setting is done right, don't overlook this setting cos it's a bit tricky, if you've done it good you will get good idle.if very good then very good idle ...... and slightly faster and smoother idle.

Good luck with excellent setting and idle and without vacuum leaks!

[tr8er]

 

My Hitachi carb adjustment story was much less fun than my Weber 38/38 swap. It is the first thing to go on a stock L-series

[ggzilla]

Hitachi is adjusted using exactly the same method as a Weber 32/36. No difference. I've seen many Webers that are worn out and won't hold an adjustment (mainly caused by worn throttle shafts).