I appreciate that diagnois by web site is a dark art but here goes.
One of my customers has the above little red beastie which does sterling work mowing a couple of acres of lawn (I know as I have the dubious pleasure of sitting on it for 6 hours mowing every week).
Over the past 2 weeks it has started to run rough after the engine has warmed up. By this I mean when the choke is off and at full throttle with cutter engaged it starts to die then recover, die then recover, etc. The solution I have found is to apply 1/4 to 1/2 choke. It does the same if I disengage the cutter but not so dramatically.
I have checked fuel filter/supply which is fine and the air filter is clean. There is plenty of oil in the engine and the petrol is unleaded (not 2 stroke by mistake). I make sure the cutter deck/grass ejector doesn't get clogged up and the drive belts are all free to turn/uncluttered.
The problem gets worse if I run the petrol tank dry before refilling (no fuel gauge). I use a tun dish with inbuilt filter as a double precaution to stop debris getting in the fuel lines/pump/carb.
It had a full service in the Spring and as far as I can tell all kill switches work properly. There are no unusual noises or smells so I can only think it is something to do with fuel supply?
Can anyone suggest what might be causing this please or what I might try in the way of first stage diagnosis?
As we know the grass is enjoying this mixture of sunshine and rain so I don't want it down at the mower engineers workshop unless absolutely necessary.
Many thanks,
Bernard
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If a pump is fitted check pipes are okay, not perished, and check pump works by turning engine over with pipe into carb removed again. Most of these models are gravity fed though without fuel pumps.
Fuel use age is way higher with blades engaged so it does all point to a fuel fault, but another issue to be aware of on these machines is that the grass box sometimes does not make a good connection on rear safety switch. This is made worse by weight of grass as box fills causing the engine to backfire or miss as box fills. This only works when cutters are engaged so it may be related? Certainly worth looking at if all else fails.
Derek and Mib,
Thank you for taking the time to send me your suggestions. I will be going through the steps you both recommend on Monday (I work in this garden 2 days a week) so will report back.
I have also bought some Redex and Carb cleaner spray as it occured to me last night that a can we use for premixing of 2 stroke was empty when I arrived Friday so I am guessing that the owner did a spot of mowing over last weekend, ran the tank dry then used the petrol left in the 2 stroke can to get the mower back to his garage as opposed to towing/pushing it. I'll be checking the plugs to see if they are sooty.
I'm pretty sure it's not related to the grass box as the problem occurs when the box is off but I'll double check the wiring/connectors, etc.
I keep my 2 stroke mix and my petrol in seperate containers to stop exactly this sort of thing happening.
Once again thanks for your advice,
Bern
Hi Bernard, It could be something as simple as a new spark plug ? I have known plugs to break down and give a weak spark when under load. Worth checking. Good luck.
Took the plugs off this morning. Both fine, no cracks or deposits and colour/wear good.
Put reddex in tank.
Ran engine to get some through the fuel pump - which took a few seconds more than I anticipated.
Put tiny drop in the inlet ports of the carb R/H then L/H.
When it went down the R/H inlet a relatively large clud of smoke poped out of the exhaust not the same result from the L/H port.
Air filter clean, housing sitting tightly on all faces and no debris present. Fuel filler cap on.
Ran the engine while mower stood for 5 minutes then engaged cutter over smooth, rough, sloping ground on short then longish grass. Ran it on low and high revs. Turned it off then on again. Ran it at fast and slow pace forward and reverse.
Mower smoothly for 45 minutes (the owner had tried on Saturday and couldn't get it to run for longer than 15).
So it looks like we have cracked it!
It even made the sunshine!!
My sincere thanks to you all, Bernard
Final update which might help those with similar porblem in the future.
I took the oulet tube off the petrol tank and found a small "wick" of debris blocking it.
Once I had gently pulled the material out petrol strated to drip out so i then used a suitable sized piece of wire and made sure there wasn't anything left then the petrol poured out freely.
I had waited for th tank to be near empty before doing this and did it on some hardcore not the client's grass. :)
Once I'd refitted the fule pipe the fuel filter filled right up and the mower hasn't missed a beat since.
Bern