I picked up a clean mower with a Briggs 104M02-0121-F1. DOM DEC 2015. The carb was taken apart and the needle was missing as well as the air filter and air filter cover. I bought a new after market carb on ebay for about $12. A new B&S are like $75. The mower started on one pull but it surged and would stall out when you pushed it. I checked all of the usual stuff like the fly wheel key, the air intake, compression is good and valves are in spec. Fresh gas and the oil is clean. It was over filled so I drained some off. As so often what is needs to happen is the jet is too lean on the aftermarket carb. I estimated it was .020 with my micro drills and I opnend to about .024 which is a good amount but it was the closest drill in that range I had. It started on one pull and idled fine. As I push it, again it begins to surge and can stall if I load it up. I let it run a bit and then pulled the plug. It looked a bit rich. That does not bother me. The Head gasket seems ok. I ran it with out the shroud for a bit and sprayed brake fluid around the head gasket and no change in idle. The compression seems fine per the bounce test. I am wondering if there is some other small part missing. I have not worked a lot on these engines as I usually work on older stuff. I looked at the B&S exploded view diagram and it seems all is there. What am I missing?
surging when moving
- Thread starter nbpt100
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Lawn Pro
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Incorrect numbers will not pull up Manuals, try looking again & include Code # xxxxxxx.
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Above kit after Code Date 15030800
Above kit before code date 15030900
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Briggs & Stratton 596505 Carburetor
CARBURETORGenuine OEM Briggs and Stratton ProductWARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov
shop.briggsandstratton.com
594636 Briggs and Stratton Kit-Carb Overhaul
Keep your lawn mower running smoothly with our premium 594636 Briggs and Stratton Kit-Carb Overhaul. Take advantage of our unbeatable prices and fast shipping.
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Above kit before code date 15030900
Last edited:
OEM Briggs is your best bet.
Please explain this? I'm interested. What is the bounce test? And who named it this? LOL
Start with a SPOTLESS fuel tank.
Fuel tank cap that VENTS proper.
Valve clearance in factory specs.
Boil clean the OEM carb.
Engine block cooling fins clean as you can get them.
Clean spark plug and reinstall.
Remove the ignition coil. Polish the mounting areas for a good coil ground.
Cold beer is your friend.
bertsmobile1
Lawn Royalty
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Check the manifold
The plastic ones are prone to cracking on the cylinder side .
The plastic ones are prone to cracking on the cylinder side .
I solved the problem by taking out the needle from the aftermarket Chinese carb and putting it in the original Briggs Carb. It runs great now. The Chinease carb is not the correct carb for this application. The Jet tower looks different.
The bounce test is this: Lay the machine on its side. Remove the spark plug wire and spin the blade. If it firmly bounces back the compression is good enough. Not a great test, but it give a ball park estimate. If you have a compression tester you can manually spin it backward and see what kind of reading you get. By spinning it back ward you are by passing the de-compressing release. Learned that one from Steve's Small Engine Saloon.
My lesson is do not blindly trust the Aftermarket carbs. In particular the newer plastic Briggs carbs. I've Never had a problem with older aftermarket carbs.
Thanks for all of the comments and ideas.
The bounce test is this: Lay the machine on its side. Remove the spark plug wire and spin the blade. If it firmly bounces back the compression is good enough. Not a great test, but it give a ball park estimate. If you have a compression tester you can manually spin it backward and see what kind of reading you get. By spinning it back ward you are by passing the de-compressing release. Learned that one from Steve's Small Engine Saloon.
My lesson is do not blindly trust the Aftermarket carbs. In particular the newer plastic Briggs carbs. I've Never had a problem with older aftermarket carbs.
Thanks for all of the comments and ideas.
Always tip a mower carb side up and always a good idea to turn off the fuel shut off valve if present. If a shut off is not present, pinch off the gas line. There are tools specific to this but i use a small vice grips with rubber pads on the jaws to protect the line. It is Always an option to run the gas low.