Briggs 27hp V-twin

[RED-Z06 2,221]

Ignoring what its in...its a 27hp 44Q977 twin, vertical shaft.  490hrs, no smoke or noises.  I got it about a month ago on a trade, it ran "okay" but when put under a load it lost power, like it dropped a lung...1 plug seemed lighter, i ordered an aftermarket carb, immediately ran with power..but, different problem, under load it surged. Not like a lean surge though.  I had a customers mower in for a new carb..i put my new carb on his mower and it ran perfectly.  I ordered another new aftermarket carb..and same deal.  I tried a static governor reset which made no difference.  Governor appeared to be working correctly..it compensated and reacted..but it seemed to compensate too quickly.  I sucked it up, ordered the $$ oem carb, new gaskets...put it all on, no change.

 

Only thing left is the governor, i had a buddy with 10 years more experience in the industry look at it, he said its probably not the governor.

 

The only thing that im feeling hopeful about, is, if i am running it at 3600...and manually override the governor with my finger, usually the force you feel gets progressively and rapidly stronger pushing back..but this one it gets weaker.

 

Ive never experienced a governor bounce on load, <not> related to a fuel mixture problem, when the problem wasnt an overspeeding engine.

[kpinnc 12,175]

Question: are you using a pulse fuel pump? Try an electric or gravity feed and see if it makes a difference. 

 

I can't speak for the vertical shaft engines, because I've only experienced this on a horizontal: there is a known issue with these engines where the case pressure is too high for a pulse pump, and the float/ plunger in the carb can't effectively shut the fuel off. It can cause surging, and in some cases very rough and weak running. 

 

It typically comes from the oil pan gasket allowing air into the case. The last one I fought with ended up being a blown head gasket that allowed combustion pressure into the case through one of the pushrod oil galleys. 

[RED-Z06 2,221]

7 hours ago, kpinnc said:

Question: are you using a pulse fuel pump? Try an electric or gravity feed and see if it makes a difference. 

 

I can't speak for the vertical shaft engines, because I've only experienced this on a horizontal: there is a known issue with these engines where the case pressure is too high for a pulse pump, and the float/ plunger in the carb can't effectively shut the fuel off. It can cause surging, and in some cases very rough and weak running. 

 

It typically comes from the oil pan gasket allowing air into the case. The last one I fought with ended up being a blown head gasket that allowed combustion pressure into the case through one of the pushrod oil galleys. 

I fed it off an electric pump and it ran the same.  Whats strange is it will run smooth, if i rev it up, smooth, if i engage the 54" deck...smooth.  But, if i bump the governor once it starts violently ripping between wide open and idle...but if i stop it, its smooth again

[RED-Z06 2,221]

Heres a video, its running at 3600, im pushing it to idle then releasing it, then the bouncing starts. If i touch the arm it stops

 

https://youtube.com/shorts/5HupXhhI0K8?si=96oaSj-WLTnqf9S6

[Rick3478 428]

My experience with late B&S engines is that they build the governors with too much gain and insufficient damping.  The engines spec'd for generators are especially bad, as they felt overly compelled to stay exactly at utility speed regardless of load.  Lean fuel mix makes it worse.  If there's a shorter link hole, try it.  Also, leaks around the throttle shaft can make weird governor behavior if the mix changes with shaft movement.

[lynnmor 7,321]

12 minutes ago, Rick3478 said:

 The engines spec'd for generators are especially bad, as they felt overly compelled to stay exactly at utility speed regardless of load. 

A generator should run as near as possible to design speed in order to control voltage and the 60 cycles per second.

[wallfish 17,023]

7 hours ago, RED-Z06 said:

If i touch the arm it stops

Is there a spring missing or could adding one with slight tension stabilize it, like that touching does?

Just spit balling

[RED-Z06 2,221]

1 hour ago, wallfish said:

Is there a spring missing or could adding one with slight tension stabilize it, like that touching does?

Just spit balling

It has a governed idle spring and the regular governor spring.  If i increase spring pull, it runs too fast.  And thats most puzzling, because it holds 3600 solid as a dang rock..

[wallfish 17,023]

10 minutes ago, RED-Z06 said:

It has a governed idle spring and the regular governor spring.  If i increase spring pull, it runs too fast.  And thats most puzzling, because it holds 3600 solid as a dang rock..

Like one of those little tension springs that hold some of the carburetor linkages. Nothing that's going to make enough difference on the regular gov spring.

Or, what about adding some slight friction to the rod or arm somewhere? That would still allow the governor to operate. Touch your finger on the linkage rod and see what it takes to smooth it out the simulate that mechanically.   

[8ntruck 7,034]

 If you don't have an air leak at the throttle shaft, a bit of friction somewhere in the throttle linkage would probably smooth things out.

[kpinnc 12,175]

Is this a Vanguard twin, or regular Briggs?

 

The reason I ask is because my Vanguard engines have a spring on the throttle rod to take up slack. I don't see one in your video. 

Edited August 17 by kpinnc

[RED-Z06 2,221]

5 minutes ago, kpinnc said:

Is this a Vanguard twin, or regular Briggs?

 

The reason I ask is because my Vanguard engines have a spring on the throttle rod to take up slack. I don't see one in your video. 

Its a Briggs Commercial, Intek based but these have come badged as "vanguard" recently.  It uses plastic bushings in all the rod holes to prevent slack.

[RED-Z06 2,221]

Governor was intact, I replaced it anyways, no slop on the gear shaft, no play in the cross shaft, literally couldn't find a single flaw in anything.  Verified its not supposed to have any additional springs anywhere beyond the 2 in place.  

 

About to button it back up, not sure what to do that isn't "rigging".

[RED-Z06 2,221]

Update: got it all back together and its not surging at all, runs completely different as far as governor response.  Had to be a problem there that was so slight that i couldn't detect it visually.

[Rick3478 428]

On 8/16/2024 at 5:35 PM, lynnmor said:

A generator should run as near as possible to design speed in order to control voltage and the 60 cycles per second.

That's the reasoning.  Most of the things you're likely to power with a generator don't really care.  They used to build them with multiple link holes so you could adjust, but I guess that was too hard for people to figure out.  So now 100% of us have to put up with twitchy governors for the benefit of the 2% who actually have a critical load.  I guess that's progress.

[RED-Z06 2,221]

45 minutes ago, Rick3478 said:

That's the reasoning.  Most of the things you're likely to power with a generator don't really care.  They used to build them with multiple link holes so you could adjust, but I guess that was too hard for people to figure out.  So now 100% of us have to put up with twitchy governors for the benefit of the 2% who actually have a critical load.  I guess that's progress.

Most anything with a logic board or circuitry needs near pure sine wave 60hz power, i learned the hard way last year, bought a high dollar Milwaukee 11amp "smart" grinder that had the ability to increase or decrease amps to maintain a governed 10,000 rpm limit.  Used it 2x..loved it, plugged it into my generator and it worked about 5 seconds and died...dead.  called Milwaukee and they said the logic board is sensitive to fluctuations in power, that its most likely the generator surged and over corrected, hit 62hz or so..and that burned it out.  Inverter gens use capacitors to bank energy..and the computer closely controls the output regardless of input, if input surges up or down, the output is constant.  If input goes above or below a threshold, power is cleanly cut to 0hz.

 

Utility generator manufacturers have done well to try their best to create a sensitive, responsive governor, but for me its...lights, fans, freezer.  Cant even hook up my fridge because it has a computer now though.

[Tuneup 1,433]

10 hours ago, RED-Z06 said:

Most anything with a logic board or circuitry needs near pure sine wave 60hz power, i learned the hard way last year, bought a high dollar Milwaukee 11amp "smart" grinder that had the ability to increase or decrease amps to maintain a governed 10,000 rpm limit.  Used it 2x..loved it, plugged it into my generator and it worked about 5 seconds and died...dead.  called Milwaukee and they said the logic board is sensitive to fluctuations in power, that its most likely the generator surged and over corrected, hit 62hz or so..and that burned it out.  Inverter gens use capacitors to bank energy..and the computer closely controls the output regardless of input, if input surges up or down, the output is constant.  If input goes above or below a threshold, power is cleanly cut to 0hz.

 

Utility generator manufacturers have done well to try their best to create a sensitive, responsive governor, but for me its...lights, fans, freezer.  Cant even hook up my fridge because it has a computer now though.

 

Isn't that ridiculous? Never an issue running across the pond on 50 Hz and power supplies 'were' engineered to be tolerant. I'm assuming that this device is also sold across the pond and they have likely not wasted money designing a Euro-only model. Why would a tool manufacturer not make a tool that can tolerate dirty power when they're shipping to us common slobs. My county's power is known to be dirty and logic boards on refrigerators are normal replacement parts. My simple Whirlpool needed one at 2 years of age and infuriated me. I think it's a matter of the manufacturer could-not-care-less. Make it cheap. Jeez, I could build a power supply that could handle frequency fluctuations, patterned from one that runs a $6,000 DMM and is cheaply made. You're right about the capacitors, by the way. Reduce size first and then take the risk. They just don't care - simple. Wow! Sunday rant!

[Rick3478 428]

11 hours ago, RED-Z06 said:

Most anything with a logic board or circuitry needs near pure sine wave 60hz power ... Cant even hook up my fridge because it has a computer now ...

 

Shortened your quote for brevity, hope you don't mind.

There's circular logic involved.  Awhile back, some government agency decided to mandate power factor control.  They had their reasons, but the fallout was that simple, reliable AC to DC rectifiers are out and fancy, twitchy switch mode conversion is the game du jour.  Fair enough, but the other side of that is that makers now assume they always have clean power to work with, and cut corners to make cheap-to-produce products.  If your power isn't clean, it's your problem now.

 

I have a degree in Electronics Engineering, and have made a good living in design, system integration, and repair, so I know exactly how good/bad most of this stuff is.  I've watched quality and reliability decay in spite of advances in technology for almost a half century, and heading into retirement I'll be glad to be done with it.

Moovin' to Montana sooon ...

 

Last shot - do you really think your fridge needs a computer?

 

Getting down off my soap box now.

 

[pfrederi 17,743]

3 minutes ago, Rick3478 said:

 

Shortened your quote for brevity, hope you don't mind.

There's circular logic involved.  Awhile back, some government agency decided to mandate power factor control.  They had their reasons, but the fallout was that simple, reliable AC to DC rectifiers are out and fancy, twitchy switch mode conversion is the game du jour.  Fair enough, but the other side of that is that makers now assume they always have clean power to work with, and cut corners to make cheap-to-produce products.  If your power isn't clean, it's your problem now.

 

I have a degree in Electronics Engineering, and have made a good living in design, system integration, and repair, so I know exactly how good/bad most of this stuff is.  I've watched quality and reliability decay in spite of advances in technology for almost a half century, and heading into retirement I'll be glad to be done with it.

Moovin' to Montana sooon ...

 

Last shot - do you really think your fridge needs a computer?

 

Getting down off my soap box now.

 

 

 

my washing machine can be monitored or controlled by a cell phone  (or so instructions say never used it)  Why on earth do I want to run my washing machine from a phone....

Edited August 18 by pfrederi