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Collection, Preservation and Display of Old Lawn Mowers

RANSOMES Auto Certes

Hi and thanks for accepting me as a new member.

I'm a Kiwi and living in southern Ireland for past 21 years and recently bought a Ransomes Auto Certes 20" Mk3. They don't seem to be that common here especially when looking for parts. I have used the mower and absolutely love it's finished lawn but unfortunately its sprockets and chains need replacing badly. I have a manual for it. Can anyone tell me if these parts (sprockets etc) are interchangeable with later model machines and where would be the best pace to buy them in the UK. I have searched the forums and internet but hope that some of the local knowledge on here might be more helpful and informative. 


wristpin Sun, 28/11/2021

Welcome to the Club.

I have rebuilt lots of Marquises and several Mk3 Auto Certes but have never encountered badly worn sprockets so can only assume that yours has had a hard life. Have you got a parts manual ? If not I can post a copy on this forum. It’s quite possible that the sprockets may still be available through Ransomes dealers but they will be eye wateringly priced. I’ve just price checked the availability of the lever that disengages the cutting cylinder on  Mk3 - £139 + vat !!!!

Your best bet is possibly good used parts from an auction site.

A Mk3 that I’m doing now.


hillsider Sun, 28/11/2021

Like Wristpin I have seen chains that were badly worn but have not seen too many sprockets that would not see further action, if it would help you could post a photo of your sprockets on here and we can either confirm your thoughts or put your mind at ease about their condition.

PortrayU Mon, 29/11/2021

Hi guys thanks for your replies... much appreciated. On closer examination while running the machine I see the top sprocket part no MBB2716A is picking up and grabbing the chain and not releasing it properly which leads me to believe it may be the wrong chain fitted and not the sprockets at all. Looking at chain charts is somewhat mind boggling. Any idea what the actual size of the chain is? This is a new area for me.

I think that replacing both chains might be a good place to start before I think about sprockets as it is hard to know how badly worn they are without new ones to compare them to.

I have done other small jobs on the mower  which have improved its operation and as a first time are enjoying the experience.

Wow wristpin you sure have a job ahead of you with that project. I don't have the need to go that far thankfully, but I can't even remove the splined shafts for the transport wheels. left or r/h threads? do they unscrew at all or are apart of the main shaft which I suspect.

wristpin Mon, 29/11/2021

Post an image of the offending sprocket. As far as I know, the chain is 1/2” pitch, 3/16” between the inner links with 5/16” diameter rollers. A bit cold to venture out to the workshop to measure one!

PortrayU Fri, 17/12/2021

My apologies for my tardiness. I have been a little busy and have managed to source the correct chain which fitted yesterday, works lovely in operation. I also had problems logging back in here which was finally resolved by swapping to firefox.Wierd!

Here are a few photos of sprockets,clutch plate and blades drive dogs. the drive digs don't engage easily without lots of grating sounds so I'm leaving them engaged until I can figure out what the problem is. Open to any suggestions. Thanks.

Sorry about the quality of the pics

wristpin Fri, 17/12/2021

Assuming that the dog clutch is properly adjusted*  the best way to engage it is to make sure that the engine is idling slow enough that the centrifugal clutch is not driving the top shaft. Then move the cutter clutch lever to the engaged position and then rotate the centrifugal clutch drum by hand until you hear the cylinder clutch “ clunk” into engagement. Then , provided the dog clutch is fully engaged, speeding up the engine should take up the drive without any grating.

*. When properly set up and adjusted sliding collar is fully engaged there should be clearance between the pegs on the “ horseshoe” lever and the collar . If, in the engaged position of the lever, the pegs are still in contact with the collar the drive will not be fully engaged and accelerated wear will result. In your images, the collar looks to be in good condition, so, hopefully the corresponding dogs on the sprocket are as good.


PortrayU Sat, 18/12/2021

Thanks for the advice, I will follow up on that. As you made no comments on the other pics I am assuming they aren't in too bad a condition. one of the next jobs is to make a grass catcher as it came without one and as I have already mentioned parts are hard to come by here.

Thanks for the advice, it is much appreciated.

Merry Christmas

DJD Sat, 18/12/2021

I worked at our local golf course between 1980 and 1981, we used a Ransome's Autocertes to mow the eighteen 'aprons' around each green with it, about three widths on each as I remember, occasionally had to do the greens with it too when other machine was out of action, even when things got wet we had to finish the job once started, I've walked a few miles behind that machine, I can tell you.

PortrayU Mon, 20/12/2021

Do the splined shafts for the transport wheels come off? I find the nuts incredibly tight and are not game to try with too much force for fear of breaking something. I have no need of them as I don't have the wheels anyway and find them catching on various things around the lawn edges

PortrayU Mon, 20/12/2021

That's a lot of mowing. One thing I have noticed is that I have been able to cut wet grass with it not like a horizontal slasher mower. I have only done the lawns with it a couple of times and they have never looked so good.Looking forward to next spring.