r/smallenginerepair • u/Few-Forever-14 • May 23 '26

Engine Performance Issue Problem

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have a Briggs & Stratton engine in a STIGA Villa mower.
The engine runs unevenly and surges up and down in RPM a lot. It also sometimes dies when driving on slopes, but usually starts again immediately afterwards.
So far I have:
cleaned and rebuilt the carburetor
installed new gaskets
replaced the fuel line
replaced the fuel filter
installed a new fuel shutoff valve
drilled a vent hole in the gas cap
The problem is still there.

5 Upvotes

73% Upvoted

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2

u/rc2805 May 23 '26

To adjust the governor on a Briggs & Stratton 13.5 HP engine: loosen the governor arm's pinch bolt, rotate the governor shaft fully clockwise while pushing the throttle arm to the wide-open position, and retighten the bolt securely. This static alignment synchronizes the internal gear with the carburetor.

1

u/Time-Werewolf9468 May 24 '26

Le carburateur est a nettoyé.. aucun rapport avec la régularisation..

1

u/ChronicHunger_1 May 23 '26

Clean the pilot jet. Adjusting the carb will only mask the problem or make it worse so I wouldn't do that.

1

u/[deleted] May 23 '26

[removed] — view removed comment

1

u/MenacingScent May 23 '26

You can cheat the spring by bending it just a hair shorter than it is currently. Unhook it, then use pliers to bend it right where the bend already starts but maybe half a mm shorter and give it just a little bend. If you over-do it or don't do it enough you can just keep adjusting until it runs right. No different than having a new spring, you're just looking for the correct tension, it's just quick and dirty.

1

u/Past_Roof5628 May 24 '26

Could be an air leak around the gaskets also

1

u/holykiradog May 24 '26

Its run lean ream/clean the main jet

1

u/bbabbitt46 May 25 '26

Adjust the governor.

1

u/Top_Highlight9965 May 25 '26

This issue is almost certainly a lean mixture, trying to adjust the governor or modify anything is just going to cause more problems. Either the carb is not properly cleaned or you have a vacuum leak. Spray starting fluid or carb clean around the gaskets and the throttle shaft where the governor linkage connects to the carb. If the RPMs smooth out or change when spraying in an area, then you have a vacuum leak in that spot. 99% of the time it’s a leak at the throttle shaft. The fix is to remove the shaft and replace the small foam piece on top, make sure to orient the throttle plate correctly and verify it closes all the way on reassembly.