Lawn mower revving high

**loopyloo** · 09-09-17, 11:03 AM

I've always fixed my own cars but never been much good at working out problems with small engines.
I just bought a brand new 4 stroke mower from Bunnings.
Put it together, added the oil and fuel and it started first go really easy, beautiful !
BUT, it revs flat chat no matter what position I put the throttle lever. The lever has choke in the throttle closed position.
I removed the air filter cover when the motor was stopped to check and the butterfly moves from fully closed to fully open when the lever is operated.
I'm taking it back for an exchange (not happy because the shop is 25 miles away) but I'm curious what might be causing this.

**mandc** · 09-09-17, 11:30 AM

Probably a stuffed governor. There should be an external spring or springs attached to a lever on the side of the block and to the throttle to control the speed

**loopyloo** · 09-09-17, 08:21 PM

Originally Posted by mandc

Probably a stuffed governor. There should be an external spring or springs attached to a lever on the side of the block and to the throttle to control the speed

Yes I know about the governor but I wouldn't have a clue how to adjust one.

So here's an update :
I took it back and exchanged it for another brand new one exactly the same....and I mean exactly the same,,,,assembled the handle, put in fuel and oil, started right away, beautiful, BUT revs flat chat same as the first one. Cannot make it slow down.....

WTF!

**loopyloo** · 09-09-17, 10:48 PM

Ok so I just watched a couple of youtube vids about setting the governor.
They say to loosen the governor lever hub then retighten while holding the lever fully clockwise and the shaft fully clockwise. That sounds ok to me but where do I set the throttle lever ? or doesn't that matter ?

**VroomVroom** · 10-09-17, 08:14 AM

Bunnings lawnmowers are often a cheap copy of something like Honda or Briggs . each have different governor systems so its hard to fault find without seeing a photo of which one you have.

**ol' boy** · 10-09-17, 08:17 AM

Originally Posted by loopyloo

BUT, it revs flat chat no matter what position I put the throttle lever.

Put some 4" lawn under it, its hungry!

**loopyloo** · 10-09-17, 09:11 AM

Strange throttle I reckon. It has 4 detent positions, which you would call choke, low, med and fast. Not sure why they thought detents are a good idea.

Crossed out is engine brake lever.

**loopyloo** · 10-09-17, 03:31 PM

Originally Posted by VroomVroom

Bunnings lawnmowers are often a cheap copy of something like Honda or Briggs . each have different governor systems so its hard to fault find without seeing a photo of which one you have.

This ones a Yardking brand, the motor only has Yardking on the cowl label but the instruction book has Briggs and Stratton written on the back page.

**loopyloo** · 11-09-17, 12:03 AM

Another thing I found :
There is a spring that goes from the bottom of the governor lever to a second lever which has a pivot in the middle. The top of the second lever stops at an adjustment screw, which I think might be for idle speed adjustment.
I've drawn them on roughly yet they are actually behind the main plate. That spring and the second lever are always rattley loose no matter where the throttle or governor lever is moved to. Having said that, I did not look at it when the engine was running.

**VroomVroom** · 11-09-17, 08:51 AM

ok , that second lever and spring are supposed to be rattly loose. there is no direct connection between the throttle plate and the throttle lever , just this second lever and spring that you described. When the engine runs , the governor lever ( middle of second photo ) pulls back on the spring , which then attempts to close the throttle. as the engine slows the spring tension is relaxed by the governor which then allows the throttle to open a bit.
under low or no load there wont be much governor movement but when load increases this will be more pronounced. It sounds to me like in your case the governor is not putting enough tension on the spring to close the throttle. most likely bad factory adjustment imo but its under warranty so you cant fix it yourself

**loopyloo** · 11-09-17, 09:38 AM

Originally Posted by VroomVroom

ok , that second lever and spring are supposed to be rattly loose. there is no direct connection between the throttle plate and the throttle lever , just this second lever and spring that you described. When the engine runs , the governor lever ( middle of second photo ) pulls back on the spring , which then attempts to close the throttle. as the engine slows the spring tension is relaxed by the governor which then allows the throttle to open a bit.
under low or no load there wont be much governor movement but when load increases this will be more pronounced. It sounds to me like in your case the governor is not putting enough tension on the spring to close the throttle. most likely bad factory adjustment imo but its under warranty so you cant fix it yourself

I have to have a go at fixing it because it has a replacement only warranty. They were a promotional item and I think they are all sold out now. If I can fix it I'll have a pretty good mower, but if not I can get my money back but I'll have driven 100 miles wasting fuel and wasting time assembling 2 mowers for nothing, then I've still gotta get another mower.

**gordon_s1942** · 11-09-17, 03:13 PM

If you intend to keep that mower (seriously consider getting a refund cause if its crook now, whats it going to be like tomorrow?) there is a small engines motor book available that covers those 4 and 2 stroke Briggs and Stratton motors.
It was printed by Gregory's and is numbered 199.
Check Supercheap, Repco or AutoOne or your local spare parts dealer.

**loopyloo** · 11-09-17, 04:49 PM

So I contacted Briggs and the guy said a lot of the new mowers don't have an engine speed adjustment (throttle). They just run fast but governed.
I argued why does it have a throttle lever then ?, as you would.

So I thought I'd better have a closer look.
The book calls the thing on the handle bar that you can move up and down a throttle, but it's actually the choke (adjustable ???)

Once the air filter assembly was removed I could see there's 2 butterflies. The so called throttle IS connected to the choke butterfly and the governor is connected to the (true) throttle butterfly. Briggs was right....
There is also an adjustment screw for the throttle butterfly which I guess is to set highest speed.
Not sure why the Chinese engine manufacturer decided it was a good thing to do but that's the way it is.

**VroomVroom** · 12-09-17, 08:48 AM

Ok , well i havent seen that before its ass about to what makes sense. Dont know why you have the engine running faster than what you need to ? Full throttle for long grass would be ok but just for your average trim its a waste of fuel.
that also explains the flywheel brake , i cant see an ignition kill switch anywhere. Pulling that brake handle open for anything more than a few minutes will soon give you sore fingers.

**Skepticist** · 12-09-17, 09:45 AM

That mower is self propelled according to the add link posted?

How does it regulate the driving speed?
I'd have expected it to be a centrifugal clutch setup but that would imply a variable motor speed with a minimum at idle so it doesn't take off autonomously

**loopyloo** · 12-09-17, 12:06 PM

Originally Posted by Skepticist

That mower is self propelled according to the add link posted?

How does it regulate the driving speed?
I'd have expected it to be a centrifugal clutch setup but that would imply a variable motor speed with a minimum at idle so it doesn't take off autonomously

Single speed defined by the engine revs. Squeezing the lower bar against the handlebar engages it like a clutch.
Another reason to be able to control the throttle since ya have to walk at a brisk pace, not good when doing edges.
I thought about adding my own throttle cable but not sure where to put it at this stage.

**Skepticist** · 12-09-17, 09:57 PM

You're putting me off affordable self motivated mowers now - all sounds very strange
The old victa is pushed around by weetbix and coffee

**gordon_s1942** · 13-09-17, 01:20 PM

The couple of self propelled mowers I have used seem to have 2 choices, go like buggery and cut or stroll sedately and bruise the grass!!
Even 'Ride-On's' seem to have this same problem.
Self propelled are great for large areas where it is fairly level and dont need lots of direction changing due to obstacles like paths and garden beds.
My yard has a slope on it so I found the best result with a self propelled was to cut 'Up Hill'.

**lsemmens** · 13-09-17, 07:27 PM

I've used all varieties over the centuries. Heck I even mowed an entire school (including oval) with a push mower once. If you've got a big area, a good ride on is the way to go, otherwise just push the thing.