Briggs & Stratton 122M02-0001-F4 spitts fuel air mix out of carburetor

[Phil P]

Hello

I have a Briggs & Stratton 122Mo2-0001-F4 that is hard to start and only runs a minute or so and quits.

This engine is on a walk behind string type weed cutter. It has only had one tank 0f gas run thru it. When it quit like it ran out of fuel. Fuel was added and this 8unit has not run since.

Has good Spark, good spark plug and I have checked and made sure the gas added is good gas and not diesel or something.

What I observe so far is when primed with the primer ball the engine will start and accelerate to about half the rpm it should operate at and then stall. By removing the air filter and observing the carburetor intake port I see a lot 0f fuel / air mix spiting out of the carburetor intake.

I removed the air filter housing and when I put my thumb over the air intake when I pull the start rope I feel as much pressure as I do suction.

Now for some questions you all mite be able to answer.

Has any one experienced this condition and is it normal

Is there any valve lap on this engine and if so how many degrees?

Is there a compression release built into the camshaft?

Thanks in advance.

Phil P

 

[bertsmobile1]

:welcome:

yes there is a valve overlap buy briggs do not publish cam tomog, just wear limits.
Yes there is decompression and it is on the inlet so you will get some spitting through the carb at low speeds.
firstly check he choke is coming off fully and not accidently coming back on.
That is the eay bit.
next check the valve clearences
and then remove the muffler and check for obstructions

 

[Phil P]

Bertsmobile1

Thanks for the reply

There is not a choke on this unit it has a squeeze ball instead.

I am leaning more towards the compression release fly weight being stuck. I grew up in a Wisconsin engine shop and their S series engines had the compression release built into the intake cam lobe and they would get gummed up with sludge and hang up and this engine is acting just like an S8D Wisconsin when the compression release is stuck on.

This is a new engine with just a few hours (1 tank of gas) before I start disassembling the engine I will have my partner take it back where he got it from and let them figure it out.

Thanks again

Phil P