Motor starts to go up and down after half a hour

JohnHendrikx

Forum Newbie
Joined
May 3, 2022
Threads
1
Messages
5
Hi!
I have a husqvarna 2008 with an Briggs & Stratton motor model 31A6070113B1.
After half an hour the motor is decreasing and increasing the speed every second?
Next day the same issue after running half an hour.
There is a shaft on the motor wich is linked to the carburateur.
At the moment of the problem this shaft is influencing the carburateur ???
What is the function of this shaft? Or what could cause this issue?

Thanks in advance!

John
 

Attachments

  • 2.jpg
    2.jpg
    19.3 KB · Views: 13

SeniorCitizen

Lawn Addict
Joined
Aug 28, 2010
Threads
123
Messages
2,075
About 99% of the time when an engine with a constant speed governor surges like yours it's because of fuel starvation ( lack of fuel ) and it doesn't matter if it's a briggs or a V-!2 continental
 

Scrubcadet10

Moderator
Staff member
Joined
Sep 24, 2017
Threads
248
Messages
6,431
Thats the governor shaft. the governor maintains the engine speed.
While it's probably not the cause of your problem, it's a symptom. most likely you're starving for fuel. running lean (too much air or not enough fuel). I'd replace the fuel filter first, if it has one. Also when the surging starts, loosen the fuel cap and see if it stops. If it does stop, your tank is not venting properly. No air in = no fuel out.
 

JohnHendrikx

Forum Newbie
Joined
May 3, 2022
Threads
1
Messages
5
Hi,
Yes, first I thought the same, changed the fuel filter and also the fuel pump.
But still the problem. Also loosen the fuel cap has no effect.
Only after reducing the RPM for a while the motor gets normal but not for a long time.
Should the fuel filter be filled fully with fuel? I see only a bit fuel inside....
The fuel pump is running on vacuüm from the engine?

Thanks,

John
 

Rivets

Lawn Royalty
Joined
Mar 11, 2012
Threads
55
Messages
14,683
I’m sorry to have to post this, but if the ideas Scrub posted do not fix the problem I suggest you find a good mechanic or shop to solve the problem. Your not understanding of how an engine works could very easily cost you more money in the long run.
 

JohnHendrikx

Forum Newbie
Joined
May 3, 2022
Threads
1
Messages
5
Btw, a fuel filter is a fuel filter or needs to be specific type for this engine?
 

JohnHendrikx

Forum Newbie
Joined
May 3, 2022
Threads
1
Messages
5
Hi Rivets, I globally understand the working and would like to understand it more.
As it runs smoothly first half hour the problem can't be a difficult issue.
As the engine is almost 14 years old i don't want to spent to much money and when it's over ok...!
I
 

Rivets

Lawn Royalty
Joined
Mar 11, 2012
Threads
55
Messages
14,683
Then I’ll back out of this thread.
 

sgkent

Lawn Addict
Joined
Sep 27, 2017
Threads
30
Messages
1,679
Sounds like a fuel supply problem. One thing I might check is the oil before you start it. If the fuel is draining into the oil it will run rich until the fuel evaporates from the oil as it heats up. Do a basic tune up on it, oil, fuel filter, air filter, make sure the engine has good ventilation and grass isn't packed around it, fresh fuel topped off, new plug etc.. new hoses even from the tank to the pump. retorque the head bolts.
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
64
Messages
24,647
As he surging takes a while to happen this suggests that either the fuel supply can not keep up with the demand of the engine
Or expansion is allowing an air leak to happen

The check for the latter saturate the manifold area with WD 40 from a trigger spray pack, not an aerosol can
If the engine faulters & blows white smoke you have an air leak.

For the former you have obstructions in the fuel lines, debris in the fuel tank of tank not venting to blame , even all 3 if you are really lucky
 
Top