Briggs & Stratton issues...

[fuel tanker man]

I have a 1976 Hahn push mower with a 4HP Briggs engine. It's the old white engine, with the auto choke set up.

I have taken the carb down and cleaned it, and put in a new air filter... and a carb base gasket/diaphragm thing... the choke seems to be working right.

If you tip the mower, spark plug side down, for a few seconds she'll prime an start right up. But it won't keep running.

I don't know if the problem might be the fuel pick up... the screen on the end of that tube wasn't clogged, and I actually removed the screen just in case it might have been clogged... but the problem persists.

I can mess with the richness mixture screw a bit, and prime the carb and get the mower to run for a while... maybe to mow for an hour sometimes, but when I go back to use it next time, it's the same thing all over again... tip it for a few second to prime the carb, then it'll start and run about 2 or 3 seconds, then quit.

Any ideas?

Thanks in advance,

Dan

 

[JimPghPA]

YouTube has several very good videos on how to rebuild the carb on B&S lawn mowers. Go to YouTube and watch several of them.

Sounds like you got something out of place like the spring or the fuel pump gasket with diaphragm. Pay attention to the ones that show how and where the spring goes, and how the gasket diaphragm sits with respect to the spring. This acts as a flap valve that pumps the fuel up from the gas tank below. If your prime works for a few seconds and then it does not run there is something wrong with this fuel pump.

 

[MrMeeks]

Is there good spark across the plug? a yellow spark is very weak meaning low energy.blue/white spark is good energy. Try replacing plug.ok

 

[greenaccord02]

No diaphragm on that engine unless I'm mistaken. It's a suction based design, I think. Take the needle completely out of the carb and spray brake cleaner or starter fluid in there to flush it out. Check the needle to make sure there's no ring around the tip. If there is, use very fine grit sandpaper and follow with steel wool to remove the ring. Screw it all the way back in by hand, then unscrew 1 and 1/2 turns and adjust from there. I'd check and make sure the seal is good between the tank and the carb and between the engine and carb, too. The fuel pickup you have has a little metal ball in it. It should be able to move freely when you shake it back and forth. This sometimes will cause problems.

If you check all that mess and don't find any problem, I don't know what to say except that you might want to take that head off and see if you're valves are seating properly. The gasket is reuseable.

 

[Jared H]

Can you buy a completely new carb for it? ... my mower was doing this at the beginning of the summer. Bought a new carb for $40 and it ran like new.

B&S 6.75 ft-lb torque rating flat head on a sears self-propelled push mower.

 

[fuel tanker man]

Thanks for the info. I'll check some of these ideas out sometime this week and get back with an update.

Dan

 

[BigCahuna]

This goes into some explanation of the older type.http://www.youtube.com/watch?v=eUa3paHhGxo