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Collection, Preservation and Display of Old Lawn Mowers

ATCO COMMODORE B20 - slight fault

Hi Team 

I realise my mower is still a young un in the vintage world or lawmowers, But it makes a phut phut noise and keeps me amused cutting grass.It was my first cut of the year last week, it started first time after being ignored in the shed all winter, and cute the grass with gusto, so to celebrate I thought I would clean the bugger. 

I brushed of all the cobwebs, rust, .. took the cover off the drive shaft, cleaned out years of grass clippings that had gathered in there, and for good measure spayed with WD40, (cures everything right) 

So the clever ones by now with have worked out that ... and Im guessing now, that the friction plate is required to be friction to drive the thing forward. 

Problem, starts fine, chugs fine, blade spins, but roller drive has stopped working, (its was fine before I did the above!! ) 


So if I am correct , and I did a stupid thing, whats the best solution 


ta muchly 


PS I do have a PDF of the manual showing the components 


hillsider Mon, 31/03/2014

Hmm it would appear that you may have inadvertently lubricated the friction plates of  a clutch. You may be able to rectify this by spraying the clutch with brake cleaner,  I would suggest that you first lay some rags down below the clutch to absorb the cleaning fluid that runs off the clutch plates, then direct the spray down between the plates to wash off the oil residues. If this does not work I am afraid that you will need to dismantle the clutch to clean things more thoroughly.

The parts listing that I have just looked at showed two clutches, one is located under the cover adjacent to the engine , the second is located in the side cover containing the drive chains to the rear roller and the cutting cylinder - which one have you sprayed with oil?


wristpin Tue, 01/04/2014

Correct diagnosis ! Seen the same thing happen with over enthusiastic lubrication of the drive chains flinging lubricant onto the clutch.

The traction clutch consists of a steel pressure pate actuated by the "clutch" bail clamping a centre plate with cork inserts to a steel driven plate.This centre plate rotates around the clutch hub on 52 x  1/8" loose steel balls. The addition of WD has not only added lubrication but may well have liquidised existing grease or oil. The consequence of this is a slipping clutch which will have to be cleaned.

Remove the chain case cover and lift the mower up enough to slide it under the mower in a position to catch the steel balls when you dismantle the clutch for cleaning. Remove the chain from the cylinder to the clutch. Carefully remove the the three screws holding the pressure pate in place. Then even more carefully remove the centre plate which rotates on the clutch hub on its 52 balls  running in a shallow groove in its inner circumference. The chances are that the balls won't remain in the groove but will drop out  - hopefully to be caught in the chain case cover. If you loose some or need extra it's not a disaster as your local bearing shop should be able to supply loose balls.   

Clean the pressure, centre and driven plates with brake cleaner and put a very light smear of grease around the groove in the centre plate and carefully replace all the balls. In an unworn centre plate the balls should fill the groove with a gap for one more ball - that is correct. However if the groove is worn the gap may be bigger and it is an opportune time to add an extra one or two but always with a one ball gap.

Carefully slide the centre plate back onto the hub and refit the pressure plate. Before refitting the chain operate the clutch bail and check that the pressure plate is clamping the centre plate to the driven plate. Replace the chain - job done.

Wear in the centre plate groove is not uncommon and, as stated, can be compensated for with an extra ball or two. More serious is wear in the clutch hub caused by the balls breaking through the hardening on which it runs - sometimes caused by running with over-tight chains. A little wear here is not a problem but if deeply grooved it is not helpful. Not sure if new hubs (F016L20203) are still available but the last price that I have was just over £48.00 plus vat!

If you need to adjust the chains that meet at the clutch the whole assembly can be moved by loosening the large nut  behind the clutch hub. Can't remember the spanner size, possibly 3/4af / 19mm , but somewhere in my tool box is a spanner that I bent to make the job easier!



Steve7 Tue, 01/04/2014

I thank you for all your replies, 

Ray I was very liberal with the wd40 even the cat got sprayed.

I will ponder what to do over a beer. 


would kicking it help :)



hillsider Tue, 01/04/2014

That's ok pleased to help, after hearing that you were very generous with the WD40 I think on reflection I would follow wristpins advice and do a strip down of the clutch to do a thorough clean, this will at least give you the chance to apply fresh grease to the centre bearing.

I don't have any advice re degreasing your cat though. If the cat is as slippery as the clutch you have got to catch it first!

Feel free to let us know how you get on with the job.


wristpin Wed, 02/04/2014

SORRY seem to have double posted this and can' find out how to delete!

wristpin Wed, 02/04/2014

Once upon a time an oily clutch would have been treated to a quick blast from a carbon tetrachloride fire extinguisher!

Now undoubtedly  frowned upon both for clutches and cats!