Ransomes Mastiff (large cylinder mower)

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    Does anyone have experience of this huge beast of a lawnmower, made by Ransomes – the ‘Mastiff’?

    I am thinking to acquire one 20 years old (with a 9 hp Mag engine), but, having never used one, am wondering if this machine has any known problems that develop with it over time.

    Although Ransomes apparently produced this mower in two cutting width sizes (30″ and 36″), I only have the opportunity to acquire the bigger type at the moment – a machine that runs, but which has definitely been around the block quite a few times, by the look of it.

    Problems could be small or great. It has been mothballed for 10 years – but actually starts first time, which is amazing. It does need to run on half choke, though – though I know not why this would be the case.

    Any input on this from those that know would be greatly appreciated.


    At least twenty years old. Quality kit and actually a simple design and easy but heavy to work on.
    Plenty of used parts available and standard off the shelf bearings etc. Should you be tempted to fit a more modern engine, stop and consider that the MAG suited the centrifugal clutch in that it would tick over below the bite point but would recover and not bog down when it was time to move off. Many modern engines didn’t like the low rpm needed to disengage the clutch so Ransomes had to fit special build reverse rotation lumps with the drive taken of the half speed cam shaft.
    Half choke. Possibly just needs a thorough carburettor clean.


    Yes heavy to use,as were designed for Football fields,Check the springs,within the cutting cylinder bearings,as known to wear, and course jumping of the cylinder,giving an erratic cut.
    Clean that carb out,as there is more than lightly sludge build up init.
    As for the MAG engine,if it runs leave well alone,they were made for running 8 hour days.I still run MAG’s commercially,on Ransomes Verge cutters
    Kind regards
    HD Trust


    Thank you very much.

    I have found out now that the machine was purchased new by the cricket club before 1980.

    I am a little concerned from the last little demonstration running of the machine last week, before I arrange to pick it up next week. At very low revs, I could hear a sound rather like a bell being quietly struck, from somewhere deep down in the guts of the thing. Would you have any ideas what that might have been? It was an intermittent sound.

    How much useful information can I glean from the identification plates, by the way?



    Thanks very much for this very useful advice.

    I will indeed look at those aspects you have flagged up for me.

    Please excuse an ignorant question. Presumably this machine would have been designed to run on leaded fuel. However, that has been outmoded. Is it advisable to do anything in particular to compensate for that, though, when using modern unleaded fuel?



    I am not familiar with this particular model but have heard a similar sound on machines that have a centrifugal clutch. The noise is caused by clutch mechanism.
    Various fuel additives are available such as Castrol Valvemaster which is a lead replacement additive.


    The clanging sound is coming from the centrifugal clutch drum. They all do it when the clutch is on the point of engaging- another few revs and the clutch shoes are flung hard against the inside of the drum and the clanging stops. Similarly if you drop the revs a little from the clanging point the return springs will pull the shoes away from the drum and the clanging stops as well.

    If the clanging persists you will need to have a look inside the drum because you may have a broken return spring, but it’s unlikely. If the noise disappears when you rev it up or down I would leave it alone.

    If you do dismantle the clutch remember that the shoes are fitted in the trailing position so that they disengage cleanly. If you put them in the leading position (i.e. with the loose end of the shoe facing in the direction of rotation) it will still work and the shoe will dig itself into the drum harder the more load is put onto it; the trouble is it won’t disengage and when you get to the bit where you’ve got to turn to go back the other way it won’t stop. Handy if you’re in the middle of the outfield, but if you’re cutting your lawn your hedges will suffer badly.

    The lever on the left of the handlebar looks like a clutch lever- don’t be misled, it’s really a parking brake that operates a drum brake in the end of the rear roller!

    Good luck with it.


    I’ve bought and sold many Mastiffs over the years and was buying ex local authority MAG engined ones in the early eighties and also looked after a couple of even earlier ones with JAP crank start engines. I’ve never seen a broken centrifugal clutch spring but they do weaken over the years and the very expensive clutch centre spigot bush can wear allowing the drum to drop a fraction and bind on the back plate, preventing clean disengagement. If you clean the carb’ and can drop the tick over rpm a wee bit the clanging should go away.
    Good advice re the trailing clutch shoes: get it wrong and they will grab and snatch on engagement. Definitely stick with the MAG if you can – the machine was designed around the slow idling characteristics of the JAP and MAG engines! All sorts of clutch / gear engagement issues ensued when people re-engined them with engines that demanded a higher tick over speed to avoid bogging down when the throttle was opened.
    Re the parking brake. A small drum at the right hand end of the rear roller (landroll) . Don’t go mad with the grease gun at that end of the roller shaft or you will fill it up! On the subject of grease, Ransomes actually specified the use of heavy oil and not grease for their cylinder mowers. In case you haven’t discovered it there is an oil filler plug in the centre rear roller section that allows lubrication of the centre differential gears. A shaped dip stick was supplied to check the level and avoid overfilling.


    This may be of use. The engine shown is the earlier JAP but the chassis should be very similar to yours.


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