Home |
Search |
Today's Posts |
#1
|
|||
|
|||
Lawnmower problem
The engine keeps revving fast then slow repeatedly every second or two.
While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? The mower is a "Best Green" with a Briggs and Stratton 4 stroke engine. David. |
#2
|
|||
|
|||
Lawnmower problem
"David (Normandy)" wrote in message ... The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? The mower is a "Best Green" with a Briggs and Stratton 4 stroke engine. David. Da..stab..rk Is there a filter in the fuel line? Clogged? Mike -- The Royal Naval Electrical Branch Association. 'THE' Association if you served in the Electrical Branch of the Royal Navy Reunion Bournemouth August/September 2007 www.rneba.org.uk "Navy Days" Portsmouth 25th - 27th July 2008. RN Shipmates will have a Stand |
#3
|
|||
|
|||
Lawnmower problem
"David \(Normandy\)" wrote:
The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! Look for a slack spring in the governor mechanism; the throttle only controls the speed indirectly, by telling the governor what's wanted. Gary Woods AKA K2AHC- PGP key on request, or at home.earthlink.net/~garygarlic Zone 5/6 in upstate New York, 1420' elevation. NY WO G |
#4
|
|||
|
|||
Lawnmower problem
"David (Normandy)" wrote in message ... The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? The mower is a "Best Green" with a Briggs and Stratton 4 stroke engine. Also *DON'T* overfill with oil as too much will give a wave effect inside the case and the governor mech will fluctuate. Also check the pinch bolt on the governor arm hasn't loosened off. Loose spring on the float bowl float to the needle valve will make a difference too. |
#5
|
|||
|
|||
Lawnmower problem
On 6 Aug, 19:04, "David \(Normandy\)"
wrote: The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? The mower is a "Best Green" with a Briggs and Stratton 4 stroke engine. There is a sort of metal flap, acted upon by the draught from the flywheel, which operates the throttle butterfly. There should be a spring biasing it in one direction, making a very crude constant revs governor. Oh, and a floppy metal rod to the carburettor. The hand throttle cable in effect sets the end point for this gadget. Sounds like something wrong with that lot somewhere Equally, the choke is operated by the last motion of the hand throttle cable. Can't recall the details, I think it's a sort of cam. Again a spring is involved to force the choke device to move against the control. Something may have dropped off there. If you know the model of B&S you can probably download drawings from the web site. |
#6
|
|||
|
|||
Lawnmower problem
"David (Normandy)" wrote... The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? The mower is a "Best Green" with a Briggs and Stratton 4 stroke engine. It's called "Hunting" and is usually caused by fuel starvation. Check fuel lines and any filters for dirt but it's probably the carburettor that has dirt in the float chamber so take it off the machine, take the top off and clean it out using petrol. Be careful though, it's a precise instrument, do not damage the float or you will need a new carb. 10 min job. You can get plastic in-line fuel filters at most motor spares shops so get one of those and put it in the line between tank and carb. If you damage the paper gasket between the top and bottom taking it all apart make/cut a new one using the cardboard of a cereal packet. -- Regards Bob Hobden 17mls W. of London.UK |
#7
|
|||
|
|||
Lawnmower problem
- wrote in message oups.com... On 6 Aug, 19:04, "David \(Normandy\)" wrote: The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? The mower is a "Best Green" with a Briggs and Stratton 4 stroke engine. There is a sort of metal flap, acted upon by the draught from the flywheel, which operates the throttle butterfly. There should be a spring biasing it in one direction, making a very crude constant revs governor. Oh, and a floppy metal rod to the carburettor. The hand throttle cable in effect sets the end point for this gadget. Sounds like something wrong with that lot somewhere My mower is prone having grass cuttings building up on the 'metal flap', gives similar symptoms. Rog Equally, the choke is operated by the last motion of the hand throttle cable. Can't recall the details, I think it's a sort of cam. Again a spring is involved to force the choke device to move against the control. Something may have dropped off there. If you know the model of B&S you can probably download drawings from the web site. |
#9
|
|||
|
|||
Lawnmower problem
"Bob Hobden" wrote in message ... "David (Normandy)" wrote... The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? The mower is a "Best Green" with a Briggs and Stratton 4 stroke engine. It's called "Hunting" and is usually caused by fuel starvation. Check fuel lines and any filters for dirt but it's probably the carburettor that has dirt in the float chamber so take it off the machine, take the top off and clean it out using petrol. Be careful though, it's a precise instrument, do not damage the float or you will need a new carb. 10 min job. You can get plastic in-line fuel filters at most motor spares shops so get one of those and put it in the line between tank and carb. If you damage the paper gasket between the top and bottom taking it all apart make/cut a new one using the cardboard of a cereal packet. -- Regards Bob Hobden 17mls W. of London.UK We have a mower with the 4Hp B&S which also hunts I found using the Shell Optimax cures the problem with no adjustment needed in this setup there is no throttle adjustment ( a retrograde step IMO ) - the carb is mounted on the tank precluding fitting a filter inline. Derek |
#10
|
|||
|
|||
Lawnmower problem
"Derek" wrote in message ... "Bob Hobden" wrote in message ... "David (Normandy)" wrote... The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? Yes the Machine needs a new carburettor diaphragm. its just a small piece of rubber and they need replacing periodically. Mike |
#11
|
|||
|
|||
Lawnmower problem
"Derek" wrote in message ... "Bob Hobden" wrote in message ... "David (Normandy)" wrote... The engine keeps revving fast then slow repeatedly every second or two. While it still cuts the grass without problem it makes it's own mind up how fast the engine goes, so I alternately walk slowly behind it then have to run after it! The throttle setting has a noticeable, but small effect sometimes, but only for a moment or two. Suggestions? The mower is a "Best Green" with a Briggs and Stratton 4 stroke engine. It's called "Hunting" and is usually caused by fuel starvation. Check fuel lines and any filters for dirt but it's probably the carburettor that has dirt in the float chamber so take it off the machine, take the top off and clean it out using petrol. Be careful though, it's a precise instrument, do not damage the float or you will need a new carb. 10 min job. You can get plastic in-line fuel filters at most motor spares shops so get one of those and put it in the line between tank and carb. If you damage the paper gasket between the top and bottom taking it all apart make/cut a new one using the cardboard of a cereal packet. -- Regards Bob Hobden 17mls W. of London.UK We have a mower with the 4Hp B&S which also hunts I found using the Shell Optimax cures the problem with no adjustment needed in this setup there is no throttle adjustment ( a retrograde step IMO ) - the carb is mounted on the tank precluding fitting a filter inline. Derek I've found the cause of the problem. There are two springs near the carb. One applies the tension in the throttle cable and there is a second very small weak spring, which seems to perform some sort of stabilisation - this was broken. Until I can get a replacement spring I've hung a bit of wire weighted with a little washer from the attachment point of the spring - this seems to supply just enough tension to stabilise the engine speed. Too slack and it runs at an erratic speed but too tight and it revs like it's going to take off! David. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
747 Lawnmower ?..............Yes, this is real, a flying Lawnmower | Gardening | |||
747 Lawnmower ?..............Yes, this is real, a flying Lawnmower | United Kingdom | |||
747 Lawnmower ?..............Yes, this is real, a flying Lawnmower | Lawns | |||
Craftsman Rechargeable Lawnmower battery problem | Lawns | |||
Honda HRB535 Lawnmower problem ?? | United Kingdom |