Briggs and Stratton 300E surging bad

[Boit4852]

I thought I said in my first post too put a blade on it...... I guess my edit didn't go thru.......

Glad you got it going,,,,,, Now remember that newer style engine has small jets and does NOT like ethonal gas at all....

Plus Tard Mon Ami ~!~!

That's right. Ethanol spiked gasoline is killing so many small engines far prematurely. Maybe in the not so distant future, our incredibly stupid and corrupt politicians will rescind the ethanol requirements, but I'm not holding my breath.

 

[asdunbar90]

I have a similar problem with my Briggs 08P502 005 F1. Part of the same 300e family, model series 080000.
It's on my MTD 11A-02BT729.

Constant surging.

Blade is intact and installed on mower.

What I've done so far:
Cleaned air filter.
Switched out gas.
Rebuilt carb completely, no clogs or debris present.
Checked O-rings/gaskets for cracks, none present.
Adjusted governor.
Checked gas tank air intake port, clear.
Checked gas line, clear.
Changed length of governor spring by slightly bending attachment arm on static end, results in faster or slower RPM, but still surging.

I'm out of ideas.

One thing I can admit. The first time the mower was used it was used on heavy tall grass. I'm wondering if I "broke-in" the mower under a heavier load than I use it at now.
Would this have stretched the governor spring or somehow set the mower to expect a heavier load?

I can hold the gov static and itll run great but as soon as I let go it'll slowely start surging and then pick up to rull sin wave surge mode. To the point where if I'm mowing I'll get patches of uncut grass hah!

 

[Boit4852]

I have a similar problem with my Briggs 08P502 005 F1. Part of the same 300e family, model series 080000.
It's on my MTD 11A-02BT729.

Constant surging.

Blade is intact and installed on mower.

What I've done so far:
Cleaned air filter.
Switched out gas.
Rebuilt carb completely, no clogs or debris present.
Checked O-rings/gaskets for cracks, none present.
Adjusted governor.
Checked gas tank air intake port, clear.
Checked gas line, clear.
Changed length of governor spring by slightly bending attachment arm on static end, results in faster or slower RPM, but still surging.

I'm out of ideas.

One thing I can admit. The first time the mower was used it was used on heavy tall grass. I'm wondering if I "broke-in" the mower under a heavier load than I use it at now.
Would this have stretched the governor spring or somehow set the mower to expect a heavier load?

I can hold the gov static and itll run great but as soon as I let go it'll slowely start surging and then pick up to rull sin wave surge mode. To the point where if I'm mowing I'll get patches of uncut grass hah!

Here is what I would do if I was you. I'll skip over the the things you've already done to solve the issue. Take a short length of 10 or 12 AWG wire about 5 or 6 inches long and strip both ends back about 3/8' or so, twist the strands as tight as you can with your fingers and try to flatten those ends by squeezing with your fingers. Now, flip your seat up and disconnect the safety switch under the seat. It's a simple two-wire connector. With the connector apart, insert you custom made wire into the slots of the switch that have the two wires from your electrical supply. This will defeat the interlock and will allow you to run the engine with blades engaged without you needing to be on the seat. From here, run the mower with the blade drive engaged and observe the governor linkage with the throttle at about 50% You should be able to see if the spring is too weak or if the cable housing clamps are not adjusted correctly. Also, with the engine not running, observe the cables as you move the throttle and choke cables from idle to about 1/2 throttle. Make sure the choke cable is opening the choke once you move the throttle cable to run from idle to full throttle. My mower has separate choke/throttle cables so what I described does not apply, but, the engine (Kawasaki) is still sensitive to the the cable housing adjustment in the clamps. BTW, the jumper wire I've described is now permanent on my Exmark. I have no steep hills to be concerned about so I don;t need this safety interlock. Not only is this wire mod handy, it has helped me adjust my cables for spot-on throttle response and very accurate governor control. If you operate your mower on steep hills, remove the jumper wire after you've done your troubleshooting.

 

[bertsmobile1]

Here is what I would do if I was you. I'll skip over the the things you've already done to solve the issue. Take a short length of 10 or 12 AWG wire about 5 or 6 inches long and strip both ends back about 3/8' or so, twist the strands as tight as you can with your fingers and try to flatten those ends by squeezing with your fingers. Now, flip your seat up and disconnect the safety switch under the seat. It's a simple two-wire connector. With the connector apart, insert you custom made wire into the slots of the switch that have the two wires from your electrical supply. This will defeat the interlock and will allow you to run the engine with blades engaged without you needing to be on the seat. From here, run the mower with the blade drive engaged and observe the governor linkage with the throttle at about 50% You should be able to see if the spring is too weak or if the cable housing clamps are not adjusted correctly. Also, with the engine not running, observe the cables as you move the throttle and choke cables from idle to about 1/2 throttle. Make sure the choke cable is opening the choke once you move the throttle cable to run from idle to full throttle. My mower has separate choke/throttle cables so what I described does not apply, but, the engine (Kawasaki) is still sensitive to the the cable housing adjustment in the clamps. BTW, the jumper wire I've described is now permanent on my Exmark. I have no steep hills to be concerned about so I don;t need this safety interlock. Not only is this wire mod handy, it has helped me adjust my cables for spot-on throttle response and very accurate governor control. If you operate your mower on steep hills, remove the jumper wire after you've done your troubleshooting.

One of the reasons why we ask people to post their engine and mower numbers is so when we do not know what they are having trouble with we can look it up.
MTD 11A-anything is a push mower
B & S 08P502 005 F1 is an 8 cube" engine, a bit small for a ride up unless your name is Stiga.

 

[Boit4852]

One of the reasons why we ask people to post their engine and mower numbers is so when we do not know what they are having trouble with we can look it up.
MTD 11A-anything is a push mower
B & S 08P502 005 F1 is an 8 cube" engine, a bit small for a ride up unless your name is Stiga.

I jumped the gun about this not being a rider. However, as I described about jumping the seat switch is still valid in my opinion. If you have steep hills or ditches, I wouldn't leave this jumper wire in place.