B&S 4.5 HP Power Washer won't run without my choking carb inlet with my fingers?

OK, my bad, I let my 5 year old B&S 4.5 HP horizontal cylinder power washer sit for over a year with the same gunky gas in it. Wouldn't start without starting fluid. Fires up only with starting fluid but WILL ONLY STAY RUNNING IF I BLOCK OFF 95% OF THE CARB AIR INLET WITH MY FINGERS?

Took the carb off today, took it all apart, carb cleaner in every carb orifice, blew out all carb passages with 100 PSI, drained all the gas and replaced with new gas, cleaned the spark plug . . . . . no change!? Will only run if I choke the carb air inlet 95% with my fingers?!?!

So obviously, something is not letting enough fuel in as compared to the air hence the choking requirement . . . so what didn't I clean enough? I did not try too hard to unscrew main? jet as it was plastic and didn't back out noticably when I turned it to the left, didn't want to mess up the plastic surface in doing so. Also, did not "unjam" the fuel pickup from the bottom of the carb as I didn't want to vibrate out later. What did I NOT do to let enough fuel in in normal running mode?

Thanks!

 

There are a few different types of 4.5 hp engines, but from your description, it sounds like the classic series. Assuming it has a pulsa jet carb, I'd say you need to replace the diaphragm at minimum.

 

Thanks cheese: It doesn't have a float bowl so it probably does have a diaphragm in that gasket. Can anyone recommend where to get a replacement diaphragm/gasket part like that from?

 

My usual message. Have a good one.Geo

You need to install a new diaphram kit, it is Briggs part # 795083 or old # 495770 also Lowe's has a kit #5083 which has the same parts.
Here we go:

Remove air cleaner, there are 2 bolts that hold things together, one on the front of the tank 3/8" and one into the block 1/2", remove these bolts, now "slowly" slide the carb/tank off the intake tube and breather tube, now tilt the tank in to release the throttle linkage and waalaa the carb/tank is removed. Check the intake tube to see if the “O” ring seal and plastic retainer are still on the intake tube, if so remove them and re-install them into the carb. Remove the 5 screws from the carb/tank remove carb(don't loose the spring) now spray all holes, cracks and crevases in both the carb and tank surface with brake parts cleaner, remove the main screen(looks like a thimble), now with a small screwdriver pry out the main jet(carefully) and clean it, check the “O” ring on the main jet for damage, if it is damaged it must be replaced, reinstall the jet, it can be difficult some times to get it to snap back in place(I use the rounded end of a screwdriver handle). Remove and clean the fuel pickup stem(not necessary if the fuel tank was clean). Clean any junk/rust from the tank. Install the diaphram on the tank then the gasket(no goo or sealer) now carefully replace the carb(the spring will try to misalign the diaphram), tighten all screws a little at a time so as not to crimp the diaphram until they are all tight. Install the carb/tank in reverse order and you are done. If I missed something one of the real mechanics will correct me. Have a good one. Geo

 

Geo: Thanks for your advice, went to Lowe's and found that #5083 kit, threw her in after taking apart all the jets and voila! She fired right up and ran perfectly.

THANKS!

 

Success is a wonderful sound. Have good one. Geo