v twin wont run without choke

[horses2]

Hello all.

I have an older briggs & stratton v-twin model 407777 type 0124E1. It run fine if the choke is pulled out about half way. if the choke is not engaged, the engine will start to die, and linkage rod from the governer will go full on to full off. I have gone thru and replaced the engine wiring harness, valve cover gaskets, and rebuilt the carb. the symptoms are still there, while the choke now only needs to be engaged about 1/4 turn.

Any ideas or thoughts? the power seems to be fine when running.

Thanks,

 

[motoman]

Lots of this in the forum.The enrichment circuit in the carb is not working properly. The fuel mix must approach 14:1 for the engine to run properly. When the throttle butterfly is opened a lean-out condition is created which will not support power demand or even running at no load. The carburetor has a puddle of gas (float bowl) which can pass heavily or lightly into the intake stream depending upon demand (governor sensing load). But if the tiny passage holes are dirty or plugged not enough gas can be admitted so hand choking forces more gas into the stream. But this is over rich and will not develop power when the engine is hot, only foul the plugs and wash oil off the cyl walls, causing you more problems. Use the search function to learn how to clean out the little holes in the carb. IMO

 

[BlazNT]

Lots of this in the forum.The enrichment circuit in the carb is not working properly. The fuel mix must approach 14:1 for the engine to run properly. When the throttle butterfly is opened a lean-out condition is created which will not support power demand or even running at no load. The carburetor has a puddle of gas (float bowl) which can pass heavily or lightly into the intake stream depending upon demand (governor sensing load). But if the tiny passage holes are dirty or plugged not enough gas can be admitted so hand choking forces more gas into the stream. But this is over rich and will not develop power when the engine is hot, only foul the plugs and wash oil off the cyl walls, causing you more problems. Use the search function to learn how to clean out the little holes in the carb. IMO

Very well said. May I use this in later replies for others on here needing help? I will give you credit on all the post I use it in.

 

[motoman]

Blaz, No need to credit anything. It is good to hear some of my blather might be worthwhile. I know you are usually very concise and do not ramble on. There are many talented contributors in this forum , including you. I know the collective knowledge would make a best seller.:thumbsup:

 

[ratman482]

Blaz, No need to credit anything. It is good to hear some of my blather might be worthwhile. I know you are usually very concise and do not ramble on. There are many talented contributors in this forum , including you. I know the collective knowledge would make a best seller.

I have a similar problem on a B&S 44N777-0124-E1 which has (I think - since I purchased off of CraigsL) many hours. It surges on no choke and with choke runs (slightly) longer. Load kills it. I've rebuilt the carb - cleaned out jets and low side jets that cause surge as well as replaced gaskets, rings.... Seems to run lean and I've heard drilling out the holes (low side) could solve problem on older engines. All electric is just fine - spark - new plugs, new coils, fuel solenoid works (seen it, hear it)...new battery (13V+)

 

[mechanic mark]

https://bsintek.basco.com/BriggsDocumentDisplay/default.aspx?filename=flmqAHX-nfBhU7y

See engine specifications in operators manual above.

791230 Briggs and Stratton Carburetor OEM

Upgrade your lawn mower with the finest 791230 Briggs and Stratton Carburetor. Shop now to enjoy our unbeatable prices, swift shipping and exceptional quality.

www.briggsstrattonstore.com

manual choke
https://www.briggsstrattonstore.com/briggs-stratton-part-796258/ choke-a-matic
if part is not OEM B&S Part it is cheap knockoff.

 

[ratman482]

Yeah...tried this too. It was even worse. I rebuilt the original and soaked it and did a deep clean. Seems to be running lean - if this is still the case, I'm going to go up to as wide as 0.030" on the low side jets to see if that helps. Valves gapped to 0.005", governor adjusted, air filter new, new gas lines, fuel filter, gas, intake manifold and gaskets, fuel solenoid, battery charged, new spark plugs, ignition coils good (have fire).....

 

[Forest#2]

Your carb appears to be the dual throat Nikki type.
If you have ever seen i trun ok without a choke you have hope. Some of the China types even when new never run right.
Here is some links about that carb.
I've at times while the carb is still on the engine and running weird and also needing a chole is remove the top plate on the carb that has the three screws and use about 25#'s of air pressure into the slots. Be carful of your eyes because this will blow gas out of the carb bowl and upwards towards face. Their are couple of very teeny slots on each side that a tag wire will not even go into and this will flush them slots. You can look at exploded views of the carb at the outdoors link and get the idea.
Here is a parts list at jacks that I seen.

https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/briggs-stratton/briggs-stratton-engine/400000-699999-series/44n700-to-44n799/44n777-0124-e1/carburetor-exhaust-system-kit-carburetor-overhaul

Here is some info I've saved about Nikki carbs and repair kits for the different types and how to repair in a logical manner. If none of the links work or the video don't run just do a search using the hints for such.
With patience this will get you going if it's actually the carb.
I've seen them carbs do some weird things, like one cylinder be completely dead because the left and right chambers are completely separate. You can get an idea which cylinder/carb chamber is running lean sometimes by looking at the spark plugs and comparing their color. I've also seen them carbs cause a backfire/sputtering that acts like bad valves.
Clone replacements carbs are a roll the dice thing, but I have taken parts from clones and used in OEM and got a good run.


5 2017

Small engines repairs links

Carbs, etc

https://outdoorpowerinfo.com/repairs/



12/2022

Nikki dual throat carb repair/rebuilding links

Nikki dual throat carb tips and re-building LINK.

Guy asks about jets sizing and re-building a dual throat Nikki carb

https://www.lawnmowerforum.com/threads/nikki-dual-carb-main-jets.29187/



You tube video part 1: (newer style aluminum float bowl Nikki) USE KIT 54832 @ $7

part 2 (older model with steel float bowl) USE KIT 54833 or 54834 @ $9 each depending on the style of Nikki. See part 2 of the video to determine which kit needed.

Search on-line for

VITON o-rings for Briggs & Stratton Nikki carburetor main jets rebuild kit

VITON o-rings for Briggs & Stratton Nikki carburetor main jets rebuild kit for sale

SEE PAGE 2





Link with good info about trying to get a good run with Nikki dual throat carb on a Briggs Twin engine

Nikki Dual Carb Main Jets

Briggs V-Twin Model 44M777 0148 B1. SN 081212YG On a John Deere Lawn Tractor Engine has a Nikki dual carb. When I removed the bowl, both main jets fell out. They look identical, but it turns out there is a Left and Right main jet and they are different. There are no makings on the jets...

www.lawnmowerforum.com

AND lots of info about part numbers of jets, jet sizing.

left jet =1.18mm= .046 inches 792296

Right jet =1.22mm= .048 inches 842627

I’ve drilled both jets on the two barrel Nikki’s to .045=1.14mm


When looking for Nikki carb parts and you have a part number use Briggs as the part number instead of Nikki



Also for Briggs Nikki parts check out sawzill aprts.com click on the menu link in the upper left corner and select Briggs for the Nikki parts list.

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