Briggs & Stratton / outboard carburetor

[geary]

Guys,
I know this is not exactly and outboard related question but I’m hoping maybe a couple of you might have an answer to my problem ? I have an old snowblower (60’s vintage) with a B & S 8hp flat head engine, This past Oct I went out to try starting it in preparation for winter, it started on the second pull and ran great ! Dec. I decided to try it again, it fired a couple times then quit, it has electric start so I gave that a try, still wouldn’t run just popped a couple times so I figured maybe water in the gas ? Drained the tank and filed with fresh non-ethanol gas, pulled the carb and cleaned it,(not really dirty) !

Everything back together, I tried again, no luck just pops a couple times ! So I thought maybe it has low compression, checked that ( 80 – 85 psi ) Not really bad for 50+ year old engine ! Pulled the head to see if maybe the valves were the problem, timing of them is correct for opening and closing but thinking I’ve gone this far I’ll pull the valves and see how the seats look ? They looked Ok but I thought as long as I have it this far
apart I’ll lap them in and check the clearance .008 on the intake and .011 on the exhaust close enough for that old an engine !

Just to cover anything I might have missed I pulled the flywheel as these type of B & S engines have an aluminum key on the shaft and are notorious for sheering, it looked fine with no indication of being sheared !
I also checked the spark and even changed from a points style ignition to an ignition module which has great spark !

Ordered a new head gasket and put everything back together, checked compression (110psi ) Should be good to go, gas on, choke closed hit the electric start. again no go, just a couple pops and backfires ! I am stumped ??? A friend said he thinks it’s a carburetor problem, so my next attempt to get it going is to make a new manifold and try an outboard carburetor ! The carburetor on it is an updraft style and I’ve had it apart so many times I could do it in my sleep. If this doesn’t work I don’t where to go to figure out why it won’t run ?? Any suggestions will be GREATLY appreciated !

Gary

[Mumbles]

You don’t mention what model number the motor is but I’m thinking it’s the one with the square gas tank above the starter and the up draft carb with a brass float? It has a module so it can’t be the points or condenser. What about the spark plug? Small engine plugs tend to go bad so it wouldn’t hurt to put a new NGK in it. Fuel flow? Is the gas fresh and does the gas flow freely out the hose at the carburetor end when the shutoff tap is turned on? The brass float can develop a leak to and get heavy which causes flooding. Carbon buildup on the valves face or seat would increase the clearances but without knowing the model number, I don’t know what your clearances should be. Here’s some specs:

https://outdoorpowerinfo.com/engine_specs/briggs_valve_gaps.asp

[green-thumbs]

I had same problem with a Toro Started ri 524,
Try a fresh spark plug of correct type gapped to spec.
Louis

[kerry]

If you decide to pull the flywheel again, definitely replace the key. Looks can be deceiving! I learned my lesson years ago, always replace it when the flywheel comes off! Cheap insurance, I usually keep a few spares in the parts drawer.

If you have too many, AND not enough, you're a collector.

[geary]

Mumbles, Thanks for the things to check, I think it’s a 17000 series but the model tag is missing so can’t say for sure, but yes it has the Sq tank above the electric starter and an updraft carb with the brass float ! Been thru the carb several times, float floats no leaks, carbs clean, gas flow is good and gas is fresh. Cleaned the valves when I did the valve lap job and the clearance is almost perfect according to the specs sheet you sent !

Green Thumb, it has a New NGK plug.

Kerry, I will pull the flywheel again and replace the key as you suggest, I can’t believe it could be something that simple but I’ve been fooled before

Thanks guys for the suggestions and ideas, I’ll let you know if I have success !

Gary

[billw]

I’m not sure whether it has a low-oil shut down device, like some Tecumsehs; but if it does, try disconnecting it and try a restart. They are known to fail on Tecumsehs. That’s gotten me a couple of times….

Long live American manufacturing!

[necks]

You mentioned you checked valves, head gasket, flywheel, etc. Without knowing
what year it is, look on shroud, it will tell you what model, type, serial number the engine is. It’s been awhile since I played with one, there should be a couple head bolts that are longer then the others, they go to the muffler side, flywheel key is what times engine, make sure it is in good shape. Use torque wrench on all nuts & bolts and tighten to correct tightness. All it takes is a kickback from the engine to shear the flywheel if the flywheel nut is not torqued to correct specs.
You mentioned you had carb apart, did you adjust mixture needles?
Find numbers on shroud, then look up torque specs for engine, then check bolts & nuts for correct tightness. I guess the other problem could be the choke, when motor is cold, I would pull motor over first, if it didn’t start the I would choke it until it fired, then take choke off, easy to flood. Just like working on outboards, check and clean, retorque everything, is real important.

[crosbyman]

My honda s.b. gave me trouble the last 2 winters with heavy sputtering…& flare ups . strong dose of Seafoam cleared it right up 🙂

I do not know about B&S carbs but honda carb copies are dirt cheap on amazon so I ordered one…. but with the seafoam fix I never changed it.

I always run the s.b. on high octane no ethanol gas…& seafoam

Joining AOMCI has priviledges 🙂

[Author]

Posts