Mower stalls on throttle

[Hobsini]

I've inherited a ride on lawnmower but not been able to use it. It starts but as soon as you add some throttle/power it stalls. It will run ok-ish with the throttle in the lowest setting but nothing more. Any ideas on what it could be or what I can check?

I have checked fuel is getting to the carb - and it is. When it is restarted after stalling it tends to kick out a lot of smoke (white) and it has backfired a few times. It was stored and unused for quite a while which may be part of the problem.

 

[Burnerman]

Probably some deposits in the carb float bowl which are interfering with the main jet, but post back with the engine type?
A new spark plug would help in due course, but the backfire is usually due to a weak fuel mixture chuffing back through the carburettor.
John

 

[big-all]

as an aside
old petrol can go off so a fresh tank off fuel not a top up go clear off any building just drain and flush through with a bit off fresh putting into a suitable container as you flush

 

[Hobsini]

Hi, thanks for the replies. It is a Hayter H1842 mower with a Kohler engine. Not sure which model engine but found the manual for the engine which covers the following models:

CV17, 25, 620, 730, 740, 750.

The manual says not to try and service the carburettor yourself!

Hope that helps.

 

[Burnerman]

Aha the Kohler V twin....these are very similar in construction to the Briggs and Stratton Vanguard V twin engines, but of course parts aren't interchangeable.
Now, this is where the fun starts.......your engine may have a twin choke carb made by Keihin (one choke per cylinder) or it may have a single choke carb by Nikki or Keihin.
I'm afraid you are going to have to photograph the thing, with the rectangular air filter removed if that's possible to help us to identify which one.
John

 

[Hobsini]

Ok, thanks will do.

 

[Hobsini]

Are these pics any use?

 

[Burnerman]

The first pic, with the two pipes, is the fuel pump that works from crankcase pressure pulses to deliver fuel from the tank to the carburettor. The cylindrical white thing is a fuel filter.
The two pipes you see are fuel into, then fuel out of, the pump. The other pipe around the back provides the air pulses from the crankcase.
The lower pic is of the air cleaner inner plate......to access the carb and remove it, you have to remove those two flange nuts, if you want to go ahead. It looks like you have a single choke carburettor, which is the simplest of the carburettors that could be fitted.
If you want to bash on, you'll need an aerosol of carburettor cleaner from a motor factors at the very least - and a compressed air supply is very useful.
John

 

[Hobsini]

Thanks. I bought some carb cleaner in advance - just in case. Happy to have a crack at it although suspect I will need some further advise. I am also unlikely to get to this for a few days now. Thanks for the help and will post again when I try and proceed with this.

 

[Burnerman]

A pleasure.....just be very careful disconnecting any rod linkages to the carb, and if there's an electrical connection to a device at the bottom of the float bowl, that's a fuel shut off solenoid and it's fragile.
John

 

[Hobsini]

Ok, I am ready to have a crack at this now. Once I have removed the two flange nuts, what do I do next? Do I need to remove the carburettor or can I clean it/spray it in place?

 

[Burnerman]

The carb has to be dismantled, unfortunately, but do wash all of the exterior gunge away before undoing it from the motor.
Disconnect the fuel pipe, then release the linkages without bending them.....sometimes the carb has to be removed before the linkage can come free.
John

 

[Hobsini]

Are you able to tell if it is the Keihin or Nikki carb?

 

[Burnerman]

The Nikki carb is a twin choke one, and the Keihin is a single choke device, which uses a branched manifold to feed each cylinder.
Either way, with care and patience (and not losing any of the bits) dismantling isn't too bad!
John

 

[Hobsini]

Ok, thanks. I got quite a long way with this but got stuck because there are one or two thin metal rods connected - which seem to connect the throttle and choke - and I am not sure how to disconnect them. I think if I can do so and they are also easy to reconnect then I could remove the carb reasonably easily.

I did also try cleaning it in place and it seemed to improve the problem but not fix it. I do wonder whether there are other issues though. For example I have not yet removed the part at the bottom of the carb where the float is. Could that be contributing to my problems?

Mower starts ok but dies when you give it more throttle.