Briggs L head runs rich no matter what I throw at it.

bertsmobile1

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  • / Briggs L head runs rich no matter what I throw at it.
IF the fuel is dripping back out of the carb then it would normally be a float problem but as this is a tank mounted carb with an overflow bowl that can't happen.
So something is causing blow back through the carb
Two sources of blow back at cranking speeds
1) breather
2) valves out of adjustment / time

On side valves it would normally be something preventing the inlet closing or the exhaust opening
Exhaust opening includes furry things dead in the muffler blocking it off .

On OHV engines it is generally excessive exhaust valve lash causing excessive valve overlap .
 

ken2

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  • / Briggs L head runs rich no matter what I throw at it.
Seems to me dad had a similar problem with two brand new Briggs 12.5hp when he was a Snapper dealer. He ordered high altitude jets and that solved the problem.
 

fixit1ddh

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  • / Briggs L head runs rich no matter what I throw at it.
Probably has plastic cam in it that has slipped a few degrees. Reason why You are getting the spitting fuel from carb. And sounds like its running rich.
 

Fish

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  • / Briggs L head runs rich no matter what I throw at it.
Drain the fuel out except for what is in the carb, then run the engine until the system is dry, and note the engine performance as the last of the fuel is burned up.
 

RescueMowerRepair

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  • / Briggs L head runs rich no matter what I throw at it.
Thanks for all the replies. I've been out of town a few days so that's why the delay on my response. Sorry I'm not quoting everyone who's posted here.
As far as the float level-
This is not a tank mounted carb.
I already verified the needle being stuck open is not the issue. it holds pressure, and cutting off the fuel inlet and letting it burn the fuel in the bowl does not improve the rich condition of the spitting fuel.
I also-
checked the valves and found zero lash. Which tells me the valves have worn deep into their seats, or ?? But this would be possibly causing both valves to be hung slightly open no? Would that cause a rich condition?
I also verified that if you pull the (new) air filter it ever so slightly improves, and furthermore, I can lean it out if I force feed it a dribble of air, improving it even more.

It's back on the bench to get the valves done tomorrow. I'll report back my findings.
 
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