Engine Z445/w 27HP Briggs engine surge

[Been There]

I think I am going to try one more thing before I start bending linkage rods and tangs. I have been looking at several videos of various maintenance techniques on these carbs. One thing I don't recall doing, was changing the O-rings on the two jets. In fact as I recall one of them fell out (though that may not be the case. Could be faulty memory). I think I'll get those and change them out. I don't want to start tweaking anything just yet. Besides it mows just fine and runs very smoothly as long as the blades are engaged. It also runs smoothly at low idle. I should probably check to see that the governor and rod are set all the way clockwise. Anyway I need to order some parts and a technical manual!

Thanks for the help guys!

Ed

The governor system is like a cruise control system. It maintains the speed of your lawn mower or outdoor power products.
When powering a lawn mower, engine load can be affected by hills or height of grass.
Without a governor, you would need to adjust the throttle manually each time your lawn mower ran across a dense patch of grass. A governor does the job for you by detecting changes in the load and adjusting the throttle to compensate. When the engine "surges, pulsating," or lack of idle-speed control, it's usually the governor that is the problem.

The jet(s) O-rings doesn't have anything to do with the engine surges or pulsating as you mention, as carburetor jets only control the idle, rich and lean factors, and running ability. You will find this out as you continue to look elsewhere for the problem(s) to have stated.

 

[Boudreaux In Eunice La.]

In reply to your statement Been There......... Yes a carb can affect surging. I had a Nikki carb that I rebuilt and it surged when I put it back on. I had to take the welch plug out and re soak it to get it right.

 

[eldowdy]

The governor system is like a cruise control system. It maintains the speed of your lawn mower or outdoor power products.

The jet(s) O-rings doesn't have anything to do with the engine surges or pulsating as you mention, as carburetor jets only control the idle, rich and lean factors, and running ability. You will find this out as you continue to look elsewhere for the problem(s) to have stated.

I know what a governor is. I know how this one works. I don't know enough about it to start bending things willy nilly. Think I can do a bit of experimentation without making permanent changes. I disagree that a jet being bypassed can't cause a pulsing. I'm not convince it's the cause here either. I do know the o-rings on the jets weren't changed the last time I had it apart. Since it's nearing 400 hours spending 20 bucks ain't gonna hurt.

Still I am very grateful for all the input!

Ed

I just had a thought (And yes it was painful!) I need to enlist my neighbor, so that I may observe what is happening when the blades are engaged. This thing run fine as long as they are.

 

[Boudreaux In Eunice La.]

Ed......

The tang is meant to be adjustable all engine companies make a tool to do that. All the tools are glorified needle nose pliers or small channel locks..

Please before you spend hard earned money on a tech manual follow my advice and just tweak that tang 1/8 of an inch to make the spring a tad tighter. I am a experienced Briggs mechanic and do this for a living. I have very good references on this site.

I wish IL Engine or Bert would chime in on here ~!~!

 

[bertsmobile1]

Why blame me ?
Generally I skim over problems I know how to fix particularly when folks who know what they are doing are already in the ring.

Now Eldowdy.
1) work out if it is the governor or the fuel system by manually moving the throttle rod , the one that connects the governor to the carb .
Start the engine and slowly move it to open up the throttle a little faster than the engine usually runs.
Hold it there for a minute or so.
If the engine runs fine with no missing then the problem is with the governor.

If the engine hesitates, stalls or misses the problem is usually in the fuel system.

Watch the exhaust for signs of black ( rich ) smoke.

Surging is usually caused by lack of fuel.
The engine starts to slow, so the governor allows the throttle to open further.
This creates a strong venturi dragging more fuel through the carb so then engine goes faster and the governor closes down the throttle, but because there is not enough fuel, the engine goes too so so the governor relaxes and allows the throttle to open up more.
And thus the cycle goes on at infinitum.
To prevent hysterises there is a damper spring fitted to the throttle rod, it s the long spring wrapped around the rod.
If this spring is missing, damaged or loose at one end the throttle rod moves to quick & overshoots in both directions but generally it settles down after 4 to 10 cycles

The balance between the governor closing the throttle & you opening the throttle is maintained by the governor spring.
When you open the throttle the spring stretches and pulls against the governor which is trying to close the throttle.
If the tension on this spring is insufficient then the governor will close down the throttle,but then the engine slows so it allows it to open against the spring , which is too weak so it closes the throttle , on & on at infinitum.

In the workshop , we run the engine on high idle then with the aid of a tacho ( oe better trained ear than mine ) we tweak the spring mounting to get the required speed, generally 3300 rpm to 3750 rpm.
This is what you are being advised to do.
On the sprint ( 3 to 5 hp ) engines it is the only way to adjust the engine speed.
I have an old Allan wrench with a slot cut in both ends to do this with which allows very precise movements .

 

[Boudreaux In Eunice La.]

Yes a allen wrench wrench with slots cut in it is a tang wrench that is very cheap to make. Everybody has one or two that's bad and a dremell tool will do the job perfectly.

Why spend 20 or 30 bucks for a briggs made tool ???

 

[eldowdy]

I'm pretty convinced it's the governor at this point. Between everybody's experienced advice it seems pretty clear. It's not missing. It's not running rich. There is no black smoke. There is no smoke at all. I will give that tang a little weak. I'll photograph it. So I can put it back if I need to.

Ed

 

[bertsmobile1]

I'm pretty convinced it's the governor at this point. Between everybody's experienced advice it seems pretty clear. It's not missing. It's not running rich. There is no black smoke. There is no smoke at all. I will give that tang a little weak. I'll photograph it. So I can put it back if I need to.

Ed

Do the finger on the governor test first to confirm.
Test first
Fix second
Convinced is no substitute for diagnosed

 

[eldowdy]

Do the finger on the governor test first to confirm.
Test first
Fix second
Convinced is no substitute for diagnosed

Yeah that's what I figured I would do. I did something similar to that last year, but I was trying to control it by holding on to the rod. I understand it better now.

Ed

 

[Been There]

Here is a perfect example of a Brigg V-Twin engine with a pulsating governor by YouTube. Check it out at about the One minute mark on the video. Note the spring reaction on the governor arm and how it plays against the engine RPMs.

https://www.bing.com/videos/search?...FC1093D49CB89A1DB99CFC1093D49CB89A1&FORM=VIRE