Cleaned Carb still need Choke

[chefwong]

I had a GX160 with a dirty carb. Picked up a brand new OE one and popped it back in.
It still needed a tune....I drained the gas, stuck it in the corner of the garage and never came back to it.

Now, 2 years later, I'm grabbing stuff out and decide to prep this as well.
Dumped it into the ultrasonic *even though technically it was a new carb*, and the water came out a bit rust'ish looking....

Fired it up. Runs a bit rough with choke until warmed up.
When warmed up, choke off, a very minute surging.
I've yet to put a load on it...

---Same GX engine---I fired up as well, while prepping. No surge with choke open or closed on a cold engine.
Whaddya guys say. Carb is still dirty or sometimes, it is what it is...

 

[Trav]

Surging = 100% it still has some dirt in it, pull the jets and use compressed air to blow the passages out in the body I assume this is an Al Gore carb with no adjustment for the mixture.

 

[eljefino]

My Chonda GX clone needed 2.5 jet up-sizings to run right without surging. I bought a hobby drill bit kit on amazon for this specific job.

It's on a snowblower.

One jet size for running at 30 degrees instead of 60. (Denser air.)

One for the ethanol in the gas.

And 1/2 for me chucking the air filter-- snowblowers don't run them. The air's clean enough. More power!!!

Oddly, warm restarts need choke, too.

 

[BTW]

Sounds like the air jet is clogged. Clean it then clean it again. Once you're sure it's clean, clean it again...

 

[bubbatime]

Replace the carb with a $14 eBay carb and don't look back.

 

[yeehaw1960]

Make sure you clean the entire carb. The passage on top is the one everyone misses. Instructions follow...

Assuming you have the non metal (top) screw type, turn the plastic screw in that keeps the idle from falling below a certain level. Count the number of turns it takes to bottom out. Remember that number and remove the screw completely. The "plastic plug" that is exposed is pressed into place. Gently pry it up with a flat head screw driver. After it's out, you need to ensure the tiny (TINY) passage that goes through the tip and comes out where the larger holes are on either side is clear. A bristle from a standard wire brush is stiff enough and small enough to clear that passage. Once that's clear, (with bowl removed) blow air down in the hole in the carb where the plug came out. A little carb cleaner down that hole couldn't hurt. Reassemble it the way it came out, by pushing it in and tapping on it until it bottoms out. It will only go in two ways, both of which are correct. The flat spots on either side are your guide to reinserting it correctly. Reassemble and hopefully it will help. Does the mower idle like it's on steroids...you screwed the screw in too far.

 

[The_Eric]

Originally Posted By: eljefino
My Chonda GX clone needed 2.5 jet up-sizings to run right without surging. I bought a hobby drill bit kit on amazon for this specific job.

It's on a snowblower.

One jet size for running at 30 degrees instead of 60. (Denser air.)

One for the ethanol in the gas.

And 1/2 for me chucking the air filter-- snowblowers don't run them. The air's clean enough. More power!!!

Oddly, warm restarts need choke, too.


I had a generator come through the shop a while back that needed this treatment. When I tore into it, the main was plugged. I soaked the carb for two days, run aerosol cleaner through it, blew it out and reassembled... Surged. Tore it back apart and ultrasonic cleaned it, made sure the emulsion tube was clean, the passage up on top- everything. Put it back on... still surged. Giving it a little choke would clean it right up, so I gave up and ran a torch tip drill through the main jet. Just a couple thou larger. Fired it back up and was better, but still surged. So this time I used the same bit but "rodded" it out a little. Bam! Problem solved. My estimation is that the carb wasn't calibratd with a large enough main jet to account for ethanol and since our bulk fuel is 10% ethanol blended, it ran just lean enough to surge. This particular customer is a farmer and has bulk fuel which is also blended at 10%, so it will work out well.

 

[mk378]

"Surging" with no load is usually because the low-speed circuit isn't working. When the governor pulls the throttle almost completely closed, the engine misfires, rpm drops and eventually the governor pulls it wide open to start firing again-- the cycle repeats. I suppose if you drill out the main jet enough you could work around that but it isn't right.

Test by running with no load and override the governor by pulling the throttle lever down against the stop screw. The engine should slow down to a smooth "idle". If you can't get this even with the screw all the way in, the low speed circuit is clogged.

There are also quite a few engines out there that will normally "surge" with no load. Remember this is 1930's technology still in use.

 

[boraticus]

Agree.

Low speed circuit is likely still clogged.

Now hear comes the "you should never do this" recommendation: Find some very thin, copper wire, usually one strand from a piece of braided wire, then clean the jets and orifices with that followed up with a squirt of WD40 and compressed air. Copper is soft so it won't cause any damage. Just don't break it off in an orifice or gallery. I've done this for years and despite the objections of nay-sayers, it works.



Originally Posted By: mk378
"Surging" with no load is usually because the low-speed circuit isn't working. When the governor pulls the throttle almost completely closed, the engine misfires, rpm drops and eventually the governor pulls it wide open to start firing again-- the cycle repeats. I suppose if you drill out the main jet enough you could work around that but it isn't right.

Test by running with no load and override the governor by pulling the throttle lever down against the stop screw. The engine should slow down to a smooth "idle". If you can't get this even with the screw all the way in, the low speed circuit is clogged.

There are also quite a few engines out there that will normally "surge" with no load. Remember this is 1930's technology still in use.

 

[The_Eric]

Originally Posted By: mk378
"Surging" with no load is usually because the low-speed circuit isn't working. When the governor pulls the throttle almost completely closed, the engine misfires, rpm drops and eventually the governor pulls it wide open to start firing again-- the cycle repeats. I suppose if you drill out the main jet enough you could work around that but it isn't right.

Test by running with no load and override the governor by pulling the throttle lever down against the stop screw. The engine should slow down to a smooth "idle". If you can't get this even with the screw all the way in, the low speed circuit is clogged.

There are also quite a few engines out there that will normally "surge" with no load. Remember this is 1930's technology still in use.



If you're referring to me, then I actually loaded the generator down with some power tools and got the same result.

As for the 30's tech still in use- are you thinking of the old hit 'n miss engines? Those really didn't surge so much as they would selectively fire the cylinder to maintain a constant RPM.

 

[TFB1]

Originally Posted By: bubbatime
Replace the carb with a $14 eBay carb and don't look back.

Agreed, exactly what I did four years ago, ran perfect since...