OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs plastic carby

Hi MM,
you don't have another tank and carby to put on it to see what is going on, never seen any carby I could not control by shutting the governor butterfly

You just use a flat blade screwdriver and press them out from the inside the carburetor throat.

Also a few of these nozzles had a brass jet installed that would fall out over time and get lost once the carburetor was removed.

Thanks very much AVB. Removed it by pressing from inside with a 7.5 mm brass rod. O ring is perfect.

The nozzle is 1.5 mm I/D Could run a 500 cc single motorcycle on a main jet that size :-)

Noted it has some numbers, 1 and 3 Maybe other sized nozzles are available? I tried to wade through the seven pages of carby spare parts on the B & S website but gave up, it's a dog's breakfast of a website.

I do have spare carbs Norm.

Will see if my B & S dealer can help with other nozzle sizes, otherwise will start modifying what I have on hand. Wish I was still back in the old days when I was doing watch and clock repairs - would have had a suitable supply of thin brass shafts and tubes and collars to whack into the end of the nozzle to play with different fuel flow rates.

Stating the obvious it is only a 148Briggs, they are a dime a dozen, just put another carby on it in 5 mins you will find what the problem is,as I said if you shut the governor butterfly you can control the revs and then it is a problem with the governor springs. Put another carby on it and if it does the same it is the governor

Yes Briggs tries to be just as secretive as all other OEMs on the specs. I like those Nikki jets they give you the PN but not the size. I gotten a few crossed but that only what I have used myself. And our EPA here has also cause problems as they don't think the techs have the brains to correctly jet an engine.

I do admit there some out there that couldn't get out of a wet paper bag with both ends open.

Norm, on some of my mowers I disconnect the governor system and have the cable operating the throttle/butterfly valve directly. Call me a Control Freak :-)

For some mowing applications I like to be able to set the motor running at a particular speed, e.g. idling very slowly when emptying the catcher, or at a fast idle when doing a very light cut with razor sharp blades.

Pics below will show you the set up on the little Lawnkeeper.

BTW I note that B&S have carb options for High Altitude mowing. I presume that means smaller main jets - less oxygen means less fuel flow or a rich mixture would result. From contact with Muricans who are using chainsaws in the tall mountains they need to fiddle around with their carbies.

And you can't understand why it doesn't run right? I walk away from this topic

This morning mixed up some 2 pack tank sealant which is impervious to petrol. Pushed it into the end of the nozzle and after a few hours it had cured enough to run a 0.3 mm drill through. Because it was still a bit soft the hole ended up about 0.5mm. Carefully picked out any swarf and re-assembled the carb (with the original brass butterfly plate), a few pushes on the primer and gave the cord a couple of pulls and the motor fired up nicely and was able to be throttled down to a lovely smooth idle.

QED - the main jet was far too large for this motor.

The governor mechanism on these mowers pulls the throttle further open when the load slows the motor down and the cooling airflow drops.

It does nothing to the fuel flow through the carb or the air/fuel mix.

Thanks again AVB, your advice on how to remove the main nozzle was extremely helpful.