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Small Engines (Lawn Mowers, etc.)/late 70's-early 80's 8hp Briggs mod.190412


QUESTION: really appreciate all the help. finished lapping and setting valve clearance today. now I can get the engine to fire with starting fluid in the carb but still wont run. will have to redo a leakdown test i suppose. how common is it for the crank seals to go bad? wondering if that isn't why I'm not getting enuf fuel mix in the cylinder.

ANSWER: Never had an issue with the crank or crank case seals on these engines.

If it starts by priming then the compression and ignition including mechanical and electrical timing are good.  This only leaves the carb as the issue.

Make sure you clean the valve breather with carb cleaner.  It should rattle when you shake it.

If it will start by priming I would make sure you can keep it running for about a minute by priming; then you know for sure there is a carb problem.

Those carbs can be tricky to get running as they age.  I have several special tools I made to help repair those carbs to include a special lapping tool to lap the taper on the main fuel jet.  This along with a special teflon washer will fix the leaky main jet issue on those old carbs.  I would check the carb shafts for wear.  I have seen really wore shafts on these engines cause severe air leaks where the carb would not draw fuel due to the air leaking in around the butterfly shaft.


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QUESTION: it doesn't run,just wants to fire. is it hard fixing this carb,or would it be easier to replace it? what carbs are interchangeable?

ANSWER: I would try fixing the carb first.  A kit will be about $25.

Briggs and Stratton 394693 Carburetor Overhaul Kit(Used Before Code Date 84100800)

Briggs and Stratton 398235 Carburetor Overhaul Kit (Used After Code Date 84100700)

Do you have an air compressor to blow air through the carb to clean the passages?


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QUESTION: i soaked and rebuilt the carb. everything in it is new. blew it out making sure air flowed thru the whole thing. bowl is filling with gas. never had such a headache from a machine. set it all to recommended settings with no luck. got the kit straight from briggs. have to check shafts and such i guess. figured after the carb cleaning and kit it would start right off but no such luck. it ran for just a little bit after the kit,and then just quit and can barely get it to fire now. it fires good when i pour gas in the cylinder thru the plug hole and that's it. backfires when choking the carb to try and start. hate to give up on it being i have a hundred some dollars in to it.

Is you carb the same as the one in this video?

In the video he shakes the float which works 99% of the time.  However, I have had some floats that were completely full of fuel and did not make any sloshing sound but you could feel the weight different when compared to a new float.


Small Engines (Lawn Mowers, etc.)

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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