OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Two Stroke Lawn Mower Frames Briggs 2 stroke on a Granberg Parksman

I had this dropped off for a service, and I seem to recall a thread about someone not having seen a Briggs 2 stroke engine.
Fuel mix is 50:1.
I've worked on a couple of these before, and this one is missing a black plastic, semi circular shroud from above the spark plug. Excuse the blotchy look on the plastics, still a little wet in the pics.

The base is a Granberg Parksman, from Hawthorn Vic. Interesting in that the pressing is stainless steel, and is a 20 inch cut.













Throttle in off position


Throttle in run position


Throttle in choke position

First time I have seen one thats not on a masport , pretty darn powerful motor if you ask me.

They certainly are, they don't seem to stuggle very much. They're quiet too, just 69db.
Just have to get it to stop choking on fuel, even with the air filter off. Float level's good, just seems like there's no metering. Oh well, I'll get it sorted. lol

Does it flood when the engine's not running but the fuel is on, Greg? If so, that would explain it.

No, only when it's running. Spits fuel back out the carb. If it had reeds, it'd be easily sorted. There's no adjustment on the carb for metering either. Just jets that I've cleaned out.

Just had a thought. Needed to be in the shower to figure it out! lol

Blocked muffler, although it does let some gas through! It would cause the symptom of it blowing back through the carb, making it appear to be choking on fuel! Compression has to go somewhere! I'll have a look and let you all know. Wasps love making nests in mufflers around here. lol

Silly me!

There are two common causes of 2 strokes spitting back through the carburetor: blocked exhaust port or muffler, and lean mixture. The difference between the two is that if the mixture is lean, the fuel will be expelled violently and will probably be burning (known as a "spit", and quite noisy when it happens). However you should also inspect the sides of the piston (through the ports) for scoring. A piston scored on the intake side does not shut the intake port off properly, and it will puff back a bit during crankcase compression.

Problem solved!!!!



Pesky little blighters!!
Runs like a dream now! hahaha

Thanks for keeping us posted Greg. I can't see a blockage in the picture. As a rule of thumb though, if a muffler is a lot heavier than it used to be, it's time to do something about it. People use different methods for cleaning them out - cook them then tap them on something, burn them out by sustained full load and full throttle, even cut them open and weld them up afterward. Aside from getting the engine to run properly again, the main test is what they end up weighing compared with a new one.

Just a thought, maybe in area where wasps have a habit of making their homes inside mufflers....how about cutting a leg section out of a old pair of the missus panty hose and slide over the muffler when it has cooled down, therefore screening the muffler opening....problem solved! Just make sure the missus is not wearing them when you cut the leg out!!

You'd have to do it each time you used it though, Deejay. It would be more fun to spend all your waking hours laying in the weeds close to the parked mower, with a can of bug spray in your hand, waiting for the queen wasp to come. Pith helmet and camo uniform are optional.

Yeah grumpy!!

hahaha. The camo I might be able to come up with. Been wearing the stuff for 12 years, 2 weeks to go!



But yeah, I will be suggesting to the owner to keep it covered when not in use!

Also, for the records, this type of wasp nest has a negligable weight, so being able to determine by weight is extremely dificult.

I dug it all out with pointy things, and then used the cutting tip on my oxy set to burn out what was left.

A bit of metal fly screen material could be used over the hole of the muffler, I have a 8hp briggs fire fighting pump with a spark arrestor that looks like mesh over the end of the exhaust, it would also stop the wasps.

These briggs 2 strokes like to be worked hard and run at 50:1 fuel ratio If you run them at 25.1 and the motor is not under load they tend to smoke a bit. I am a contractor and run the same engine on a granberg base. It only gives a slight puff of smoke when cold. Anyway my point is I found the easiest way to clean carbon from this muffler is to burn it out.
The trick is to heat with a gas blow torch inside the muffler until the carbon is glowing red.
You then apply compressed air to the red hot carbon and take the blow torch away. The carbon will continue to burn away so long as you keep the air on it. Do this to both ends ie the engine port side of muffler and inside the baffle end ie exhaust exit."works a treat"