Briggs 10 HP Generator engine lean surging

[Fordace]

Hi Guys,

I was on the old forum a while back. I had to re-register.
Usually I can fix these small engines myself as I have been doing it for many, many years, BUT this one is being a pain in the A$$.

Coleman Powermate Generator circa 1997, I purchased brand new.

Briggs 10HP model 19E412
Type 01-07-01
Code 9701071A
Walbro LMT 172 Carb (19E400 carb I believe)

Coleman Generator always ran fine, have owned it since April 1997, only used it maybe twice a year since then, but always maintained oil in like new condition, and kept gas fresh.
Well, it's running lean, and I have taken the carb apart and inspected it, it was clean, but I disassembled it all and cleaned it with carb clean and compressed air.
Put all back together, same thing, will surge unless you run it at 1/2 choke or better. So, I figured, I'd get an over haul kit (497849) for the Walbro LMT 172.
So, I completely disassembled it again, this time taking the throttle shaft out, bushing, choke and shaft, idle mixing circuit welch plug I guess they call it.
Pulled out the old fuel inlet seat and pressed in a new one, changed the main nozzle, float is good, new needle etc...
I dunked it in the new carb acid for 45 minutes, cleaned it real good, completely blew through every port and orfrice etc with a needle blow gun. Keep in mind this thing was clean to begin with, at least I couldn't see any dirt or carbon build-up, varnish, nothing.
So after reassembly, I get the same exact damn problem. I am very fed up with this non adjustable piece of crap....only idle mixture can be adjusted, no other adjustments can be made.

Does anyone know any tricks how I can richen this thing up a little without running on half choke....?
Is the a different main nozzle I can try, I'm not sure what to do. The generator runs well under electric load at 1/3 choke. With no load, you have to run it at 1/2 choke to be smooth, if you take it off choke completely, it just surges like crazy, LEAN........Thank you all for any help or advice you can give me....Rich

[Merkava_4]

I'm looking at that main nozzle Ref. #142 with the holes in it. That would be my prime suspect for not getting enough fuel if I saw corrosion in those holes. Compressed air is great for removing debris that's loose, but corrosion often times is not loose. How does the corrosion get in there you ask? From moisture present in the fuel. One of the best tricks I learned from the guy who owns the mower shop is to take a torch tip cleaner wire used for cleaning torch tips and stick the wire that fits the best (there's several different size wires) in the hole and rod out that white corrosion. You don't want to enlarge the hole. Just clean it out.

Ref. #94 is the idle needle kit. Does your engine have that? Or does it have a high altitude needle? The best way to tell is the high altitude needle will be larger in diameter and NOT have a backing spring. The high altitude needle is meant to be screwed all the way in and left that way. It's not an adjustable needle. You'll be running lean at sea level if you've got the high altitude idle needle in there.

Welch plugs. You mentioned removing the welch plug, but you may not have gotten the holes behind the welch plug clean all the way by using compressed air alone. That's where that torch tip cleaner comes into play.

If it was me, I'd probably just clean all the holes that I could find with the torch tip cleaner and then install that rebuild kit Ref. #121 that has the new main nozzle. Then I'd make sure I had me an adjustable idle needle and not that high altitude one. Oh yeah, installing a new welch plug would be a good idea too.

[Mek-a-nik]

The ultrasonic cleaners mentioned on this forum quite frequently work much better than dip, in my opinion. They also work quicker and neater, too. I don't even use my dip any more. You can use many different cleaners in it. I've been using a combination of vinegar, baking soda, and Simple Orange-type cleaner. (No explosions yet. )
I'm mobile, and can't afford to wait for a dip to work. I put the carb parts in the ultrasonic, and then do the billing, clean up, whatever, while it works. 10 or 15 minutes.
Maybe this will help you get the "yuk" out.
Of course, make sure there isn't another problem. A vacuum leak or something.

[Fordace]

Hi and thanks for the responses...

So, I guess ultrasonic is the way to go these days. I knew they use that when rebuilding fuel injectors.
Basically I wanted to know which circuit in the carb you guys suspect being clogged, could it be one of those tiny idle circuits that you cannot really access?
Behind the welch plug, I made sure those circuits were perfectly clear, like I said, this carb was very clean to begin with.
On the side of the carb there looks like a small steel plug of some sort that looks pressed in, it's not a ball, but looks like the head of a small finish nail (sorta) and it is steel.
Maybe behind that?? That was something I did not take apart.

Thanks, Rich

[Merkava_4]

I think you're over thinking the situation. As long as all the passageways are clean and the float level is
correct with the inlet valve sealing like it should, and with the mixture set correctly, it SHOULD run right.

[Fordace]

Hi,

There are no mixture setting srews, that is the problem. If I had those, surely I could correct the lean condition.......Thank you, Rich

[Arkie]

Read the info at this link about LMT carbs! (it's a perr link and a guy has similar questions, etc about the LMT carb) Has some pic's of the carb orfices and holes!

viewtopic.php?f=14&t=172

and you can do a google search and bring up lots of good info about these type LMT carbs!

And your wrote this!
[b]Coleman Generator always ran fine, have owned it since April 1997[/b], only used it maybe twice a year since then, but always maintained oil in like new condition, and kept gas fresh.
Well, it's running lean, and I have taken the carb apart and inspected it, it was clean, but I disassembled it all and cleaned it with carb clean and compressed air.
Put all back together, same thing, will surge unless you run it at 1/2 choke or better

Adjustable type jets in your existing carb is not going to get er going for you, even if you could do such!
Your carb is just a little bit bad, which is similar to being just a little bit pregnant, and you cannot adjust out the hunting and leaniness because it's restricted inside, assuming you do not have a air leak at a gasket between the carb and the engine!! (don't hurt the messenger)

any of the small orfices being restricted, even the idle side will cause your leaned out hunting issues, because it's also taking part of it's fuel through the idle orfice at the high rpm's!

You may be at the point of considering buying a harbor freight Ultrasonic cleaner if the above tips don't fly or replacing the carb! (may also have to replace the carb after using the $65 HF cleaner)
(also keep a heads up and don't get the governor set at a very critical setting of the governor arm holes while working on the carb or it will hunt with a good carb) I make a witness mark on the correct hole for the governor arm before removing and I also check the static setting per the manual if it's still hunting somewhat or not carrying load properly during final tuning)

Just a heads up that Coleman is now Pramac America and has a good support dept for the electrical section and parts lists if you ever need any wiring diagrams of the generator section, etc! (you can google search and come up with email and phone numbers)
AND yes the hunting and surging is really aggravating on a gen and it's good news to hear that this is a BRIGGS instead of a TECUMSEH! You made T-man's and my day as usually this symptom is on a Tecumseh and the engine get's a severe molesting and bad mouthing! If it were a Tecumseh we would also suggest that you go to Church before working on it any further!

[Fordace]

Thanks, I wont mention my Tecumseh HM80, (I think that's the engine) hunting on my snowblower.....OOOOOOOOPPPPSSSS

[Merkava_4]

Hi,

There are no mixture setting srews, that is the problem. If I had those, surely I could correct the lean condition.......Thank you, Rich

No you couldn't - because even if you corrected the lean condition at a certain RPM, you still wouldn't have the necessary fuel VOLUME that you needed for the higher engine speeds.

[snovin2]

I have the same problem as first stated in this thread.
I replaced the old carb with a brand new OEM one and still have the same problem. The engine will only run on full choke or slightly off (like we're talking a sixteenth of an inch).
I have also replaced the diaphram in the fuel pump,new fuel lines and fuel filter,new spark plug(which has a nice blue spark)air screw is completely shut off(screwed in) also new air filter but runs the same with or without the filter.

Is it possible the main jet in the carb needs to be bigger and if so what can be done about this? (drill it and to what size)
I assume it is not getting enough fuel being as it will only run with full choke.

Any help would be appreciated thanks in advance.

It has a walbro lmt 172 carb.
briggs engine numbers are 19E412 0107-01 9610174YD