1993 McLane edger

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Briggs 3.5hp engine - 91202-0149-01 93082303

Bought off facebook marketplace for 25 bucks. He couldn't get it running. Guy put a Chi'sneeze ebay or amazon carb on it. Engine will start and run for the most part okay. Most part meaning there is a weird rumble sound out of the muffler. Sounds like it's missing about 45% of the time.

Valves are right on at 0.006" INTAKE and 0.009" EX. Was shocked to see that especially on a 1993 engine. Course edgers don't get all the hours like mowers do.

Pulled Chi'sneeze carb off. Noticed there was only like 1/4" to 3/8" of fuel in the tank bowl. This is a pulsa jet carb with a fuel pump diaphragm.



Pretty sure that entire tank bowl should fill with fuel and spill back out inside the tank. Anyway there is a lot of dead space in my bowl unless it evaporated in the garage??

Luckily he kept and gave me the OEM Briggs carb. Yup I'm putting her back on all cleaned up. Cleaned the jets with monofilament fishing line. No torch tip cleaners required LOL. Going to slap the carb back on tomorrow night.

Ok what I found was the big hole in the Chi'sneeze carb, where the fuel pump spring and diaphragm protector ring ride, that big hole is a smidge too small. The diaphragm protector ring barely would go inside the carb body. In other words not much fuel pumping action going on. No wonder the bowl was darn near dry. OEM Briggs hole allows the diaphragm protector ring to plunge inside the carb body fully and then some. Just one more reason NOT to buy aftermarket parts I guess.

Oh and the fuel pump spring is noticeably/slightly heavier than the OEM Briggs spring. I bet she runs like a top now.

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Anyone bore out the fuel pump spring hole yet? My Chi'sneeze carb only needs a couple thou taken off. Aluminum body and some 120 grit paper might do it. Put a nice polish on it after I get the proper size.

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Wondering how far the fuel pump spring and diaphragm protector ring, how deep do they plunge into the carb body? OEM Briggs carb has a small boss to limit the depth travel into the carb. Chinese carb had one but not as defined. Think I'm having a fuel bowl fill up issue. When I remove the carb there is roughly a 3/8" to 1/2" of fuel in the tank bowl. It doesn't fill the bowl and spill over into the tank like it's supposed to. My Chinese and OEM Briggs are doing this. Even with a new fuel pump diaphragm in the fuel pump.

1.Fuel pump isn't filling up the tank bowl and spilling over into tank.
2.Engine seems to run a touch lean. It hunts against the gov spring. If I near close the choke or cover with my hand it will smooth out a bit. Can't remove the main jet in these pulsa jet carbs, that I know of.
3.So not filling the fuel pump bowl fully is making the engine run lean'ish. Makes sense as a normal carb with a low fuel level will do the same. I mean this one is not even close to spilling over into the tank like it should. Wondering if I need a stronger diaphragm spring or what? Again I installed a new diaphragm in the pump.
4.New carb to tank gasket and carb to engine block gaskets. WTF??
5.Pilot needle adjustments make NO difference. I can remove the needle while running and nothing changes, surge surge surge.
6.Think I need to remove the welch plugs and make sure the holes are open.

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Removed both welch plugs. Sprayed, blew and rodded all holes. Every carb hole is totally open and clear. Still surges. Compressed air and carb spray city.

Sprayed ether where carb mounts to engine. Engine smoothed out for a couple seconds. I though ah-ha vacuum leak. Removed carb and slathered on a thin layer of RTV on every surface. I was confident it would not surge. Slightly more than finger tight for the first hour. Snugged up a couple hours later. Surge surge surge with 1 gasket WTF. Might have to try 3 gaskets. It had 2 on it when I removed the carb. This is with the OEM original carb. Guess it's flange flatness check time. Funny the single paper gasket looked to seal on both sides....

Now fuel tank bowl is half full when removing carb. Guess it won't stay full as the carb main jet boss area will displace some fuel.

 

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Thinking about slathering RTV all around the carb flange to engine intake port. Just to see if that will seal it. Again the carb had 2 gaskets on it when I opened her up. That didn't seem to work either. Going to cocoon the sucker up with RTV silly cone and see what's up.

 

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Recap on the surging

Tank and fuel bowl are clean
OEM Briggs old 1993 year carb are clean and open. Removed 2 welch plugs even to make sure each hole each way was open fully. Carb spray, paper clip and compressed air.
Slathered RTV all around the carb to engine flange to stop a vacuum leak I found with carb spray. Had 2 carb to engine gaskets when I found it.
No oil burning
Valves were spot on at 0.006" and 0.009" EX
Has new Briggs governor springs and carb linkages
New fuel pump diaphragm
Pilot screw makes NO difference all the way in or out = should be a plugged pilot circuit but no way
Fresh 100% gas with stabilizer

Giving up on the old NLA Briggs carb I guess. Guess carb is just wore out?? Think I did everything I could to stop the surge. Going to install the Chinese carb the guy put on with 3 gaskets.

I removed the plug. The thread outer ring was totally clean. Inner ceramic insulator was black (rich) as was the center electrode. Might be from the constant surging? Looking into the cylinder was a water or fuel residue on top of the piston. Could move it around with a screwdriver. Should of smelled for what it was. It was a clear liquid.

Engine acts lean. Smooths out with 85% choke on. Then the plug looks black on the electrode????

 

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SHA' ZAM - this POS is running now.

Guess the OEM Briggs 1993 era carb was it. I put the CHi'sneeze carb on. It micro surges but basically she's a runner now. Under load she is smooth. At idle (3500rpm) she has a tiny surge. Much more livable now. Might have to boil the Briggs carb like Bert mentioned. It has to have a clog some place I can't get to.

Backing up with the Briggs carb, the mounting flange on the carb was warped pretty good. Took a file to it. Used 220 then 320 wet/dry paper on a glass window to shine her up. Got her about 98% flat. SOB still surged with 2 gaskets. The Chi'zneeze carb was pretty flat.

Put a new Champion RJ19LM plug in. Made no difference on the surging with the Briggs carb. Engine manual said to use the resistor plug. Non-resistor J19LM made no difference.

Now it's off to get the 2001 Mclane edger running.

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