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Collection, Preservation and Display of Old Lawn Mowers

Suffolk Punch 35sk .

Hi all I have a problem with this mower, it will not run off choke without hunting,

It has the tillitson carb fitted . I have seen this problem with Delorto carbs but not,

These carbs . When the mower is running off choke it is hunting ie the governor

Is moving back and fourth, i have cleaned the carb out twice now but it makes

No difference.



Any advice is welcome.


Thanks in advance.



hillsider Thu, 31/07/2014

From your description it would seem as though your carb has a blockage to the idling jet system that has failed to be shifted by your cleaning efforts, it may be that your carb would benefit from a session in an ultrasonic cleaning tank. 

It would be helpful if you posted the make and model numbers of the engine and the carburettor to enable us to be sure of the carb you refer to.


wristpin Fri, 01/08/2014

As Hillsider says, gunge in the idler/progression system. Your best chance is a session in the u/s tank but even that's not guaranteed if the carb is gummed up.

Haven't got a Tillotson handy to look at but I think that they have an adjustable jet behind a plastic plug (designed to stop diy adjustment!) which, if you hook it out will allow for a bit of compensation - but please note that I said "I think"!. Don't confuse this with any metal welch plug sealing a fuel gallery.

Motivator Sat, 02/08/2014

Thanks for the advice guys . I will take the carb off later for some better pics.

I will getting hold of a cleaner soon .

wristpin Wed, 06/08/2014

When using the ultrasonic tank some cleaning solution will help or even a couple of drops of washing up liquid.

Remove all the jets etc and alter the orientation of the carb during cleaning  - say 3 quarter hour sessions with the carb differently positioned. If your tank doesn't have a heater, half fill with cold water and then top up with just boiled water.

After cleaning flush through the carb with carb cleaner or a Water Dispersant spray..

Should you have access  to compressed air, use it with care as if your carb has a replaceable float needle seat it is possible to blow it out, never to be seen again!

Motivator Thu, 07/08/2014

Thanksifor the info fella. The carb has a plastic float do you think it will be ok in the tank. One other thing when you guys say idle side of the carb , it has a large main pickup with a jet that unscrews, then there Is the jet with the needle is this the idle side of it.

Motivator Mon, 11/08/2014

Carb has cleaned up well , waiting on a new o ring for the bowl .

Fingers crossed it works .

wristpin Mon, 11/08/2014

Hope that you can get an O ring ( pt no F016S10075) as it was shown as obsolete some years ago.and I can't find it listed as a pattern part anywhere. If you find a supplier please be kind enough to post it on this forum.

Incidentally, when you first posted I spent some time trying to find your carb on line and although Tillotson have a a distribution company in Southern Ireland their website has no reference to the carb used by Atco/Suffolk/Qualcast. Seems that it may have been a special application and only for sale through the OEM.

Motivator Mon, 11/08/2014

Hi yes very hard to find anything spares wise. I ordered one from the gateshead Mower centre . If the carb is shot could you sugest a alternative. As it is a tidy mower.

wristpin Mon, 11/08/2014

I think that at various times that basic engine was also fitted with a Dellorto carb and even a Tecumseh branded one but the snag may be the mix and match with the manifold and governor etc. Those machines were made, sold and possibly scrapped in such big numbers that a complete engine can possibly be had for not big money. I know a couple of people who break mowers for parts and will have an ask.

Motivator Tue, 12/08/2014

Thanks for looking i think the carb will be good , fingers crossed.

When the ring comes and is right i will post a link.

Doug_spurs Tue, 20/10/2020

Did you manage to get the Tillotson to operate? I'm having trouble with mine and going through the multiple clean cycle you did! If you did get yours running well....any tips on "setup/tuning"?