# Carburetor requires 3/4 choke



## BradfordScott (Oct 2, 2017)

I replaced the Nikki Carburetor (#697978 - discontinued) on a Briggs and Stratton 10hp generator with an XA 591378 (see https://www.amazon.com/gp/product/B01GE1Z0MG/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1), and the engine runs great in the 3/4 choke position, but it runs really rough in the full Run position. I checked that there are no air leaks and the gaskets seal correctly. I can rev the engine just fine. But, I'm not sure why I need to choke it one notch off of full choke. Should I try a different carburetor? Or is it okay just to run it with 3/4 choke as long as it runs well?


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## Predator (Sep 19, 2017)

That would indicate that the carburetor is running too LEAN for your engine.

Some of these carburetors have adjustable main jets and you may need to adjust it.

This may help.....

How to Adjust Briggs & Stratton Carburetor


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## BradfordScott (Oct 2, 2017)

Thanks. There is an idle adjustment screw, but no other adjustments. And while I agree it seems to be running lean, I'm trying to figure out if that is a problem.


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## exmar (Jun 29, 2015)

Ah, the days of adjustable carbs before non adjustable EPA ones. :-( FWIW, I keep a set of welder's tip cleaners for use in "cleaning" the jets in the non adjustable carbs, sometimes it works.


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## BradfordScott (Oct 2, 2017)

Thanks exmar - I was able to clean the old carburetor and get the generator running just fine. But, I figured a new carb was even better, especially when the generator is only used in emergencies (e.g. power outages). So, I doubt it is clogged, as I said, it revs perfect. I'm just not sure if running it on 3/4 choke is okay for the engine.


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## Predator (Sep 19, 2017)

BradfordScott said:


> Thanks exmar - I was able to clean the old carburetor and get the generator running just fine. But, I figured a new carb was even better, especially when the generator is only used in emergencies (e.g. power outages). So, I doubt it is clogged, as I said, it revs perfect. I'm just not sure if running it on 3/4 choke is okay for the engine.


Here's the thing.......
The fuel metering process on a carburetor is very precise.

The choke system is not.....it just throws a bunch more fuel onto the fire.

So it's not likely you'll get just the right mixture using the 3/4 choke method.

So I would say no, it's probably not ok for the engine because it will not provide the goldi-locks mixture, but rather will be too lean and run hot or too rich and use too much fuel. It will "probably" run on the rich side and just use more gasoline, but it's hard to say.

You could measure the venturi butterfly valve to see if it's the same size as the old carb (it should be).
If it is, then all you need to do is up the main jet size a point or two. 

They make those carbs for a wide variety of engines and applications....not to mention the climate and elevation. Selling it with just the right jetting is difficult at best.


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