[unclejemima]

So I did my first real mow with my new to me GX85.

A little prod of the choke and it sprang to life and settles down to a nice smooth idle. The throttle is responsive and there is no bog or hesitation. In other words, it runs great.

But it run riiiiich. So much so that my wife had to close the windows the house cause it “stinks” when I was mowing. That’s a first. I stunk like exhaust when I finished as well. There is no denying that it runs rich. Really rich.

There is no blue smoke or anything…just it smells like it’s using a lot of fuel. To the point you can almost taste the fuel when your done mowing (gross lol)

The carb and fuel pump are brand new, as is the spark plug.

I live at around 3000ft elevation…it’s a stock carb. I’ve had to lean out other machines with high altitude jets in the past, and I think this might be a similar situation with everything being jetted for sea level.

2 questions.
-Does anyone know the Briggs part number for the high altitude jet?
-Is there adjustment that can be done from the carb? I see 2 adjustable screws but not sure what they do.

Engine and carb photos attached for reference. Thanks!!

 

[denverguy]

Aftermarket carb? You might be able to swap jets from original to new.

I live at a little more than 5400 feet and while I have downsized jets, the factory jets ran a little rich, nowhere near what you are experiencing. Kawasaki suggests a jet change at >3000 feet and IIRC JD recommends a jet change at > 6000 feet. My point is, that you're on the cusp of needing a jet change unless your new carb has the wrong jet size and you shouldn't be running that rich. I have several engines that I haven't reduced jet sizes on that run fine.

The sliver screw looks like an idle stop, the screw with a cap is likely a low-speed adjustment which is likely adjusted to give you the highest RPM you can get at idle - it has minimal effect on the high-speed mixture.

Any chance the float is stuck? It's a new carb but it happens.

Hopefully, someone with more direct experience with your engine will chime in.

 

[unclejemima]

Thanks for the reply!
I was ashamed to admit I got an Amazon carb…it was just to cheap to pass up…and upon comparison it’s identical to the stock unit in every way…but perhaps the main jet is larger in the Amazon unit. I’ll pull the old carb out and have a look!

More suggestions on what the carb adjustment screws do would be appreciated. I was hoping one might be a low speed idle mixture screw…? It might help the rich running at low rpm?

 

[unclejemima]

Just for fun, I found a PN for a High Altitude jet for my b&s engine. It’s supposed to be PN 694925. Though I’m not certain at what altitude they suggest changing.

I’m trying to hunt a jet down…but can’t seem to find one anywhere.

 

[denverguy]

More suggestions on what the carb adjustment screws do would be appreciated. I was hoping one might be a low speed idle mixture screw…? It might help the rich running at low rpm?

Yes, it will lean out the engine at idle and somewhat at full throttle as well unless there is something wrong with the carb.

 

[unclejemima]

Yes, it will lean out the engine at idle and somewhat at full throttle

what way do I turn the screw to lean out the mixture? Clockwise or counterclockwise clockwise?

It’s the screw with the large black plastic cap, right?

 

[denverguy]

Should be clockwise. The black cap limits the movement.

 

[unclejemima]

Should be clockwise.

clockwise (turn in) to lean out. Got it. That’s what I figured as well. Thank you!