Lawn Boy 10424 Idle Jet Replacement

[turfboy1997]

I had tried everything to my 10424 to quit surging and it still wanted to surge after three carb cleanings. Today as a last resort i changed the throttle plate to the one with a larger hole and still surging. Then i got Briggs part number 801308 and replaced the pilot jet. When i started that motor it roared to life with absolutely no surging and no smoking! If any of you have duraforce engines and have not performed this upgrade it will blow your mind the difference. It burbles like an F until you sink it in some thick grass and then i have never heard the governor on an f kick in like the duraforce did today. Every duraforce that i get will have this upgrade performed. The best part is you don't even have to pull the carb to do it because the jet is on the outside left of the carb. I don't know if anyone has started a tread about this in the past but just thought i would share!

 

[lawn mower fanatic]

for sharing!

 

[Fireman 123]

Thank you. I have one that I will have to do this to.

 

[EdBrown]

Thanks for the info. I am certainly going to change to the bs pilot jet on my Duraforce LB's.

 

[turfboy1997]

Ok I have an update it the idle jet. I ordered 10 of the Briggs part number jets and they have a much smaller hole than the one my friend gave me. I put the briggs part in and it surged a little at the beginning then leveled out once warm. It wad not near as easy to start as the one given to me. I think the hole is a little bigger than the one that came on the mower but it is smaller than the one he gave me that made such a big difference. The one that made such a big difference is out of a mikuni Wisconsin carb. All that said I am going to get some micro drill bits and drill the Briggs part to the size of the mikuni. I will report back on the sizes later.

 

[EdBrown]

Would you happen to know the size of the holes in the first bs pilot jet you received? Thanks.

 

[turfboy1997]

Would you happen to know the size of the holes in the first bs pilot jet you received? Thanks.

Its an actual mikuni jet out of a wisconsin robin not a b and s and i would have to guess its a #74 or 75 on the pilot jet on the outside of the carb. i reamed the b and s out to a #77 the other day and it still surged for a second then stopped. i am maybe going to go with a #74 or 75 on monday. i will post results.

 

[Rivets]

Punching jets (as mechanics call it) has been around for a long time. We started doing it when Tecumseh came out with the nonadjustable AutoMagic carb in to late 70's. Don't tell anyone, as it still works on the new Chinese carbs your seeing today. A couple tricks to pass on to those who are thinking about trying it. Most of todays carbs are bored to .018-.0135" which is between number drills 77-80. Only use number drills between 73-77 on today's carbs. For those that may not know it, there are half sizes, which may or may not be labeled. Example, #76=.020 and #77=.018 but there is a drill size .0197. Anything larger is you will cause a too rich condition which you can't control. Make sure that you drill very wet, I use a very light synthetic oil. Drilling dry can cause a rough surface and burrs. Never punch the high speed and idle at the same time, you'll be buying new jets the next day. Never punch the jets before you have tried throughly cleaning the carb first. Finally, make sure that you are using a good quality drill and go slow.

 

[kirkbrit]

I certainly respect you experts and you ability and knowledge to "punch jet" but I would prefer to spend a little money to solve the problem. I have an older unit, 2 in fact, that starve for fuel, and have to be primered constantly until warm. They surge, can be very hard to start and generally are a pain. I would be happy and please to:
A install a different carb
B install the carb parts that will make them run well.

It has been suggested I need a couple of springs on the carb but I don't know a part number.

Will this idel jet work on my model 10247?

 

[impalass]

I certainly respect you experts and you ability and knowledge to "punch jet" but I would prefer to spend a little money to solve the problem. I have an older unit, 2 in fact, that starve for fuel, and have to be primered constantly until warm. They surge, can be very hard to start and generally are a pain. I would be happy and please to:
A install a different carb
B install the carb parts that will make them run well.

It has been suggested I need a couple of springs on the carb but I don't know a part number.

Will this idel jet work on my model 10247?

It would seem so but i need to know the serial number to make sure.