Kitchen Garden Forum

Hi,
I have an Atco Commodore B20, age unknown but suspect 15 years or so, which has a problem I think with the ignition. The mower is in superb condition otherwise and cuts beautifully, so would like to try to sort this problem.

The engine is 114cc, has a plastic shroud / casing marked up with a sticker saying "Electronic Ignition", is not an electric start, has a J8C plug installed and seems to have the original paint on the side draught carb ( gold colour) and an oblong air filter, rounded at top, square at bottom, which is plastic and two-part - comes apart by squeezing edges together.

The problem with the engine is when cold, starts usually easily but 8-strokes most of the time when cold. When warm/hot usually runs fine for maybe 30 mins at a time at all revs and powers - sometimes reverts to 8-stroking again, but the change is instant, hence suspecting an electrical / ignition problem. I have stripped the carb down to the last part, cleaned all through ( it wasn't dirty ).

Someone suggested the engine had an ignition coil "upgrade" although another said that wasn't applicable to this engine ( not even sure who made this engine)....

Can anyone indicate what the problem might be and can I still get the part(s) needed from somewhere to cure it ?

Thanks,

Nick

Hello,
I believe the Commodore series ran from about 1983/84 to about 1995.

The A114 engine, 114cc, was the last design series made by Qualcast/Atco/Suffolk group...ie; Atcos own engine.

The ignition on all A114 were electronic....1983 to 1990? was the first type and then 1991? on was the second type...I believe they are not interchangeable..but I believe both are available.?
I left the mower world when the first type was still new so I never got to see any fail..other than being aware earlier on the A98 engine when I think there was a cable chafing problem.??
I think there were some problems with the suppressor plug cap...both with internal break down and also if unscrewed too many times it got so that the HT lead end centre wire broke up and thus the cap screwed into only insulation..?!.

At the change of ignition type I think the carb' was changed from Dellorto to Tillotson?
Champion J8C would have been the plug at new...seem to think we used to put J17Lm in some??..and I do believe there was a later recomendation to change to a NGK type to give better running on newer unleaded fuels...a local agent would advise best on this http://www.atco.co.uk then Atco owners then postcode Service agent search..similar info i think could be gleaned via http://www.qualacast.co.uk Both companies of the same group.

I am not familiar with Tillotson carb types but some Dellorto types suffered quite poor running...often a poor lumpy tickover had to be put up with to give good runing at cutting speed.. Attempts were made to sort this with at one time on Dellorto carb engines a recommendation to set spark plug gap at a massive 40 thou.!! I think with a change of recommended plug this went back to 25thou.?? I think the later ignition was 25 thou too.??

On Dellorto types the centre emulsion tube, the brass main jet tube, that screws up the centre of the carb used to get grass in its tiny side holes which often led to the ability to only run on half choke middle choke position or even to cut out off choke...

In normal running it was often a regular thing to require half choke during warm up before choke off was possible.

The only carb adjustement on Dellorto types was the tickover mixture screw on the side and then the throttle stop screw to set tickover revs. (Some troublesome engines had a retro fit adjustable main jet, this would be under the centre of the carb bowl.)
On Dellorto types..once warm, the side adjusting screw would be adjusted to optimum tickover..then there was a final setting of quarter turn richer....can't remember in this case if its an air or fuel screw.??

**Do take great care in any adjustments as whilst your attention is fully on the sounds from the engine it is easy to forget other dangers of the mower.
**Never run engine inside shed or garage etc...due to exhaust fume danger.
Best run on a lawn..because on a hard concrete etc surface this type tend to vibrate...this itself will cause erratic running.

***If in any doubt do not take any risks...all local machinery agents should still be familiar with this type...and if they are an Atco/Qualcast agent they will have had service update bulletins through the life of the series.

All the best,
Clive.

Hi Clive,

Many thanks for a great reply - I will try and discover which carb it actually has - any pointers as to how to identify as I couldnt see any marks on it ? ( or can I send you a photo?) and also how to identify / check which ignition arrangement it has so I can get one of those after I have checked the carb through again ?

Thanks again,

Nick

The Dellorto type, I seem to remember, carries its name cast into the side of the carb' ..I'm not sure if the Tillotson is marked with its name.??

And I think the ignition type change came at the same time as the carb type change.

Illustrations of the ignition coils appear here http://www.midlandpower.co.uk/spares/se ... artType/05 a trade parts provider to the machinery service agent world.

The ignitions will be rather expensive I suspect....and I think I would want to be very sure before doing a change...I think perhaps a word with a local service agent would be the way forward..??

Clive.