carb jetting question for B&S 2 cylinder engine - Lawn Mower Forums : Lawnmower Reviews, Repair, Pricing and Discussion Forum
Small Engine Repair Discussion Talk about issues or tips you may have for others regarding small engine repairs.

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post #1 of 4 (permalink) Old 05-19-2020, 01:12 AM Thread Starter
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carb jetting question for B&S 2 cylinder engine

i have a Briggs & Stratton 44N877-0003-G1 with the auto choke, so its not the 2 barrel carb, its the single barrel carb in it

i realized the main jet has fallen out so i used a spare from those standard carb rebuild kits for the 14-20hp single cylinder inteks

well the engine runs sorta as it should but clearly the jet is too small since at full throttle its only running like 1/4-1/3rd speed at best

i found another jet i dont know whats its from but it must have been a 20-21 hp since you can see the hole is noticeably larger so i'll try that in it when i get a chance.

my question is, if anyone knows, since i have at least 2 different size jets, how many different standard sized jets are there?

im assuming that the small jet size was for 14-17 hp and the larger jet size would be for the 18-21 hp but would that be enough flow for a twin cylinder engine?

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post #2 of 4 (permalink) Old 05-20-2020, 12:31 AM Thread Starter
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oh well, i was hoping someone knew something

it is a strange request after all

there are just no carburetor kits for this engine and im not keen on buying a $25 main jet for the carb and a new carb costs $200

i'll try the jet i found that has a bigger hole and see what happens

if thats not enough then i'll break out the drill bits and make my own jet

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Last edited by keakar; 05-20-2020 at 12:37 AM.
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post #3 of 4 (permalink) Old 05-22-2020, 01:02 PM Thread Starter
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ok the jets i had from the carb rebuild kits were small and the one i used in the carb was a little larger then those but the one i found with the bigger hole was just a tad bigger then the other one so i used that and it seems to run pretty good now.

but i dont think it still has full throttle. it just seems too quiet and rpms are lower then i would expect but its hard to tell and it seems good and strong and no longer struggles when blades are engaged like with the medium sized jet.

if i had to guess i would say it maybe runs about 2/3rds rpms that i would expect it to at the fast throttle setting now. but then its fairly new and being a twin maybe it is just a very quiet engine

im gonna call it fixed at this point and if she struggles in tall grass then i will bit the bullet and just buy the $25 jet for it

end result working on this mower is

- the governor arm needed replacing

- someone took the carb apart and lost the main jet and put it back together like that blowing up the in the process

- they also lost the bolts for the intake manifold so i had to dig through my spare bolts bucket to find the right length ones for it

- the cooling fan was busted up because the cover was loose with half the bolts missing on it so i had to dig through my spare bolts bucket to find them

all this on a 3yr old lawnmower but its all fixed the right way now, with the possible exception of the questionable jet issue
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post #4 of 4 (permalink) Old 05-26-2020, 03:18 PM Thread Starter
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Quote:
Originally Posted by keakar View Post
- someone took the carb apart and lost the main jet and put it back together like that blowing up the in the process

- they also lost the bolts for the intake manifold so i had to dig through my spare bolts bucket to find the right length ones for it
these should say:

- someone took the carb apart and lost the main jet and put it back together like that blowing up the governor in the process

- they also lost the bolts for the intake manifold and used the too short valve cover bolts for it so i had to dig through my spare bolts bucket to find the right length ones for it

You can only learn if you ask the question, so there are no dumb questions.
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