Z335e engine surge

[bertsmobile1]

I get mine through Alibaba
There you deal mostly directly with the factories and the vendor does not get paid for the items till I have verrified that I got it & it works .
Thus so far 100% of what I go from there have been perfect
There is a second "Ali" called AliExpress set up like Ammozone so the vendors do not have to guarantee there goods are fit for purpose in order to get paid.
SO If you end up giving up on your carb then get one rom Alibaba not Ammozone or Evilpay where all of the criminals dump defective & questionable goods .

As for our carb, your idle circuit is clogged
To clean it requires a bit more than spraying carb cleaner through it
Carb cleaner softens dried up fuel residues it does not get rid of tiny bits of rubber or accumulations of grit that have bypassed your filter .
If you have blasted the carb with high pressure air then you have probably wedged the obstructions deeper in the passageways.
In this case the carb will need to be disassembled then boiled in a big pot with a couple of dishwasher tablets dissolved in it or given a very hot & long ultrasonic clean.
I have had the odd one that took several hours in the ultrasound before it came good.
Jets & passageways should always be blown out BACKWARDS if you are silly enough to use full pressure compressed air

 

[Jonnie_S]

I get mine through Alibaba
There you deal mostly directly with the factories and the vendor does not get paid for the items till I have verrified that I got it & it works .
Thus so far 100% of what I go from there have been perfect
There is a second "Ali" called AliExpress set up like Ammozone so the vendors do not have to guarantee there goods are fit for purpose in order to get paid.
SO If you end up giving up on your carb then get one rom Alibaba not Ammozone or Evilpay where all of the criminals dump defective & questionable goods .

As for our carb, your idle circuit is clogged
To clean it requires a bit more than spraying carb cleaner through it
Carb cleaner softens dried up fuel residues it does not get rid of tiny bits of rubber or accumulations of grit that have bypassed your filter .
If you have blasted the carb with high pressure air then you have probably wedged the obstructions deeper in the passageways.
In this case the carb will need to be disassembled then boiled in a big pot with a couple of dishwasher tablets dissolved in it or given a very hot & long ultrasonic clean.
I have had the odd one that took several hours in the ultrasound before it came good.
Jets & passageways should always be blown out BACKWARDS if you are silly enough to use full pressure compressed air

Thanks for the info.
As I said in my previous post, after cleaning the carb a second time, the engine now runs perfectly smooth across the rpm range.
The only thing I did differently the second time was to fish a 30g wire through all the orifices. I never saw any debris, but something must have been in there somewhere.

 

[bertsmobile1]

You need sweet bugger all build up on the sides of a jet to drastically reduce the volume trough put
And that is before turbulance
Jets are fine reamed not drilled .

 

[Johner]

I get mine through Alibaba
There you deal mostly directly with the factories and the vendor does not get paid for the items till I have verrified that I got it & it works .
Thus so far 100% of what I go from there have been perfect
There is a second "Ali" called AliExpress set up like Ammozone so the vendors do not have to guarantee there goods are fit for purpose in order to get paid.
SO If you end up giving up on your carb then get one rom Alibaba not Ammozone or Evilpay where all of the criminals dump defective & questionable goods .

As for our carb, your idle circuit is clogged
To clean it requires a bit more than spraying carb cleaner through it
Carb cleaner softens dried up fuel residues it does not get rid of tiny bits of rubber or accumulations of grit that have bypassed your filter .
If you have blasted the carb with high pressure air then you have probably wedged the obstructions deeper in the passageways.
In this case the carb will need to be disassembled then boiled in a big pot with a couple of dishwasher tablets dissolved in it or given a very hot & long ultrasonic clean.
I have had the odd one that took several hours in the ultrasound before it came good.
Jets & passageways should always be blown out BACKWARDS if you are silly enough to use full pressure compressed air

Will almost guarantee the high speed jet has dirt in it. Are very small holes along the jet could be plugged or the main jet that screws into it is plugged , or open the jet with a screw driver. If you get a new carb sometimes that jet has to be drilled out with carburetor drills.

 

[LMPPLUS]

B&S 40N877 engine is surging most noticably at idle and low speed, but even at high speed it does not sound right. Sounds a bit rough.
Mower has less than 30 hours on it. 2 years old.
New fuel filter, air filter, spark plugs (old ones looked fine)
Fuel pump seems to work fine. I see fuel trickling into the filter. Crank the engine with the pump output line disconnected and gas spurts out pretty vigorously.
Just for kicks I gravity fed fuel from a container - no difference.
Opened up the carburetor - it looked perfectly clean. Blew out the orifices and re-assembled. This carb has a single emulsion tube, not the 2-tube version I've seen in several youtube videos.
Governor linkage and springs all good.
Fresh fuel (although it is 10% ethanol).

Read lots of posts here and in other forums about engine surging and I'm running out of things to check.
The mower runs ok at high speed and is perfectly usable, but just doesn't sound like its running smoothly. At its lowest speed it lopes badly, almost stalls.
Its still under warranty but a hassle to bring it to a JD service center. Plus, if they determine it just needed a "tune-up", i.e. normal maintenance, that's not covered.

Any ideas?

-Jon

Jonnie you commented that you blew out the orifices in the carb, you won't get out what you need to get out by just blowing air in it, in fact you may make it even worse, you have a restriction somewhere in the body of the carb soak it carb/ parts cleaner or use a hydro sonic cleaner.

 

[Johner]

This is something happened to me. Toro wood chipper, Ran great end of season. Next time I ran it would not run without choking. Persistent to find the trouble on the third time taking apart the carb, on the main jet covering one of the small holes in the main jet there was s peace of gasket material similar to Teflon tape that snuck up on the tinny hole, trimmed it off and now runs like new. Have no idea where it came from. That is how important it is to clean those small holes. Doubt I will ever see the same thing in my life as above.

 

[Johner]

Another carb problem came about fixing a customers machine, under those metal plugs inside the carb are fuel channels some with a ball bearing check valve can get plugged from setting to long. If you want to trouble shoot and see the problems use a fine tooth comb to find them.

 

[Johner]

Most carb. problems can be solved using Fuel Stabilizer. Not one customer came back after sub jesting it and I know it was not for sure what I charged to do the work.

 

[StarTech]

Most carb. problems can be solved using Fuel Stabilizer. Not one customer came back after sub jesting it and I know it was not for sure what I charged to do the work.

Many can be but there still age related and other problems that can happen. Things like worn throttle and choke shafts can not be fix using a stabiliser nor can solid materials getting into the fuel system.

 

[Johner]

Many can be but there still age related and other problems that can happen. Things like worn throttle and choke shafts can not be fix using a stabiliser nor can solid materials getting into the fuel system.

Yes there are many things. Worn throttle and choke shafts have never so far ran into that problem.