Another Briggs question

Tony Shelton

Tony Shelton

BS Detector, Esquire
16 hp briggs is loping at no load. Not so bad when the trigger is pulled. Pulling the choke partway helps a little.

It was doing it a little, but now that I swapped mufflers and put a less restrictive one on this one it's a lot worse. (had to switch with another motor to get the exhaust direction reversed.)

What should I look at first? Would the spark plugs have anything to do with it. They are pretty old now. Or is it something in the carb?
 
The main jet probably needs to be cleaned. Several years ago, I put a 16 Vanny on a gokart with straight pipes. I had to drill the jet out to get enough gas to it.
 
Tony Shelton said:
16 hp briggs is loping at no load. Not so bad when the trigger is pulled. Pulling the choke partway helps a little.

It was doing it a little, but now that I swapped mufflers and put a less restrictive one on this one it's a lot worse. (had to switch with another motor to get the exhaust direction reversed.)

What should I look at first? Would the spark plugs have anything to do with it. They are pretty old now. Or is it something in the carb?
Click to expand...

I just called Russ for the exact same issue, on the same engine. I'm gonna go buy new plugs first to see if it fixes it. Keep us posted Tony
 
Ok, replaced plugs.

Then I pulled out 142A which was filthy and cleaned out the one next to the antibackfire thing in place because I couldn't get to it without taking the whole thing apart. I cleaned every place I could get to. All of them started off somewhat restricted, but seemed to flow clean at the end.

Then I cleaned the area where the spring moves it back and forth as it idles.

Put it all back together and it still does it, just not QUITE as bad.

Runs perfect at half choke.

Runs perfect under load.

The only thing I noticed was the gasket air filter housing on top of the carb has about a 1/4 inch area where it's broken and thus has a gap in it. I know that would cause problems in a high performance bike, but I don't know if it would make a difference here.

Any ideas? Or do I get out the drill for the main jet?

PS, I tried to artificially restrict the muffler to see if it would make a difference. Burned my lips pretty bad.
 
Governor spring, move it to the next hole. Theres a standard procedure I think - if it lopes move it up and if it loses too much rpm under load move it the other way.
 
the governor-spring can make it less sensitive to this problem, but..
I believe there's two jets in there.
the main jet delivers the loaded mix, and the "idler-jet" gives it the idling mix..
If the idler-jet is closed-up, even a littlet, he engine starts to die..
.. the governor flops-open the butterfly, drawing fuel through the main-jet, and the rpms surge up.
Then the governor let's off throttle-butterfly, releasing draw thru the main-jet,
and the idler-jet tries, and fails again.
..A cycle of not enough, then too much, ..alternating.
The symptoms lean towards an idler-jet problem.
The back-pressure of the muffler simply makes it more sensitive to idleing issues.

..Now where's that parts diagram.. ? .. ? ..
(I haven't had my own hands in a v-twin carb for several years.)
 
That sounds right on the money with whats going on with mine jerry. Under full load runs like a top so you wouldn't think the main is restricted much. I'm gonna do a full carb cleaning in the morning, and hopefully be done with it.
 
Russ Johnson said:
Don't "drill out" the jet, unless it's a pin drill just to remove the layer of varnish in the orifice.

Really sounds like that carb is a mess, might just want to get a new one.
Click to expand...

Do they sell carbs at harbor Freight?
 
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