Skip to main content
Collection, Preservation and Display of Old Lawn Mowers

Suffolk 75G14 Cutting out

Enter a word or two to search the forum section and click the Search Forum button.

I have a suffolk 75g14 on a suffolk colt dual drive mower, it starts with quite alot of effort on choke, if i try to continue running it on choke it will cut out after a while but if i take it out of choke it dies instantly. i have adjusted the screws on the carby to idle one turn out and main jet 3/4 of a turn out. i have cleaned the carb and tried it without the air filter, all of this hasnt solved the problem. i dont know what to do know and i need some advice. Thanks.

Forums

hillsider Thu, 28/06/2012

Hi, has your mower engine got contact breaker points behind the flywheel or electronic ignition? if so these can be the source of problems such as the one that you are experiencing.Cleaning and re gapping should see an improvement.

Ray 

redfernmowers Thu, 28/06/2012

from having refurbished one similar to this some time ago, that type of engine needs a bit of care.

the symptoms you've given tell me that two things need to be done. firstly, as ray suggests, the contacts need to be cleaned and polished and the gap checked and adjusted. if I remember it's 20 thou. 

the second area to concern yourself with is the carb itself.

here's a service routine I use...

1: dismount carb from engine.

1a: inspect fuel hose for wear, discoloration or forms. replace.

1b: check your fuel tap for a decent flow. it may be that fuel isn't running as freely as possible. where possible, drain the tank, undo the tap carefully and clean the filter. if the filter is heavily corroded, change the tap and filter as a complete unit. these are cheap and readily available.

2: if air filter is present, remove it and take out the filter. rinse it in paraffin and dry out. do the same for the filter case.

3: inspect the float bowl both inside and out. remove the bolt under the bowl (cab specific) and the two screws above the carb holding the top plate and gasket in place. if the bowl contains dirt, rust, etc, this needs careful attention and cleaning. check the condition of the float and needle. be careful with this as it's pretty sensitive.

4: remove the needle adjuster screws making sure that you remember each screw installation.check the condition of the tips of the needle valve screws. if bent, replace them, if dirty, clean them in  paraffin and a tooth brush. 

5: immerse the rest of the carb in a paraffin solution and leave for a while. if you have either an air compressor or a bottle of compressed air, clean out the carb and let it settle. If you have access to an ultrasonic parts cleaner, prepare a neutral cleaning solution available from most ultrasonic parts cleaner specialists and have the cleaner set at about 50C and do about 2 or 3 cycles at 5 mins per cycle. this really gets into the carb and flushes out dead fuel, dirt, rust, etc and cleans the outer joints, etc. put in the needle valves, bolts, screws, float, etc.

6: rebuild the carb. ensure that you reassemble as you remember it.

7: install carb to engine and reconnect to the engine..

with fresh fuel in, start in choke and dial each screw so that you observe a noticeable change in the RPM in choke. it should be smooth. now slowly bring the engine into full run in idle point. adjust the fuel mix screw so that the engine can run in tick over without driving the blades. sometimes this can be rectified by adjusting the shoe springs / replacing them.

bring the engine to full rev and if it runs freely without diving or starving, you're ok. if it shifts in pitch, go back to the fuel mix screw and adjust until it's even. usually a 1/16 or 1/8 turn should do it.

I hope this helps out. it's what I do and it brings the engine back to life. Carbs are funny little beasts. just like women lol. you can never directly understand them fully but they get you through the day. :)

HenryB Fri, 29/06/2012

UPDATE,

After fiddling with the idle screw i can now run my engine in choke reliably however it still cuts out when taken out of choke. also it sometimes continues running when the throttle is completely closed, confused.

ps. i dont have much fancy tools, i am just a 13 year old lad trying to restore some heritage whilst learning something about mechanics.

hillsider Fri, 29/06/2012

Hello Henry,

If you explore the Mowers area of this site you will find the technical help section, in there is a heading called operator manuals. open this up and scroll through until you find the Suffolk Colt open the pdf file attached and should find a Suffolk hand book.

There is a lot of info in there that will help you in particular the carburetor that is dealt with very thoroughly. I would recommend that you set the two mixture screws to the basic setting described in the text as the engine will run at this setting until it has warmed up and then further adjustments can be made if required.

Re tools you do not need too many to work on these engines they are excellent engines to start learning on I am sure you will soon work out how to make it run. 

Keep us posted and don't be afraid to ask.

Ray.

 

redfernmowers Fri, 29/06/2012

hey and well done. it's about time us young guns encouraged others to do this kind of work. I'm really impressed that you're interested in learning the art of restoring an engine.

you don't need much in the way of tools for most engines.

As a recommendation. some useful tools for you..

General purpose socket set. ideally you'll need 1/4", 3/8" and 1/2" socket sets so hunt down a decent all in one set.

set of imperial spanners,

set of metric spanners,

set of screw drivers,

needle files and standard engineering files,

large wire brushes and detail wire brushes (Stanley make some decent ones)

I recommend a flare tip cleaner from an oxy acetylene set. you can get these cheap from any welding or engineering suppliers.

a manual valve grinding tool and paste.

a dead blow hammer and pry bar.

that should really do you unless you want to be careful about your flywheel. so if you need to take a flywheel off to get at the points,  a flywheel puller and flywheel holder would be worth getting hold of and if it's a briggs engine, a starter clutch tool which you use with a socket wrench. for a safer job of it without breaking parts.

if ever you're struggling with parts for briggs and stratton engines, go to www.briggsbits.co.uk. I find them very helpful.

all the best and please let us know how it all goes. I wish you all the best and remember.. have as much fun as you can.

 

ed

wristpin Sat, 30/06/2012

A couple of points from previous posts.

The general advice under the heading of "good workshop practice" is that one should not poke metallic objects (nozzle cleaners) through carb jets and orifices for the very good reason that enlarging them will alter their calibration. In the real world and specifically referring to the fairly crude Zenith carb used on the old cast iron Suffolk engines there is probably little risk of doing any damage that cant be tuned out with the adjustable idle and main jets  - but be careful.

I do have a set of nozzle cleaners in my tool box because I still gas weld and braze and also use it  for heating to aid the removal of stubborn components such as Hayterette blade discs - that's my story and I'm sticking to it!!Two less aggressive  options are a bristle from a wire brush or some nylon fishing line.

For modern carbs with multiple small finely calibrated orifices an ultrasonic tank has become an essential tool in any commercial small engine workshop and as the "contaminate" (- percentage ethanol) content of pump fuel increases will become more so. However, up until about ten years ago we all did quite well without one!  As a business we were an early adopter of a u/s tank and I seem to remember our all singing and dancing tank that holds two or three carbs  cost in the region of  £500 ten or so years ago but there are now some very reasonably priced ones on that well known auction site  but it could be a case of buyer beware as some are primarily designed for cleaning watches and jewellery and may not have the guts for a dirty carb..

Tips when using u/s tanks. Use the basket - don't let things rest on the floor of the tank. Keep the tank and fluid clean and don't allow sludge to build up on the tank floor.  Alter the position of the items being cleaned during the cleaning cycles - the u/s tank works by "shaking" the dirt lose and changing the orientation allows gravity to aid cleaning  - otherwise the loosened dirt can remain in drillings and passageways ready to cause more trouble!.

redfernmowers Sat, 30/06/2012

I use flare tip cleaners only for  suffolk carbs. other than that it's down to compressed air, parrafin. well... Now... very shortly, I'm taking on an industrial ultrasonic cleaner capable of cleaning large components including small engine blacks, etc. so will be using this little beauty for most work.

I too use oxy acetylene and love it to bits. it's a real life saver, like you, I also use it for the cutter heads on hayterettes. speaking of. one just arrived two days back and today started work on it. 3/4 hour later engine firing up like a dream. the old B&S 3.5hp model from the 70s

 

anyway, yep, I do agree about the use lf metalic tools to clean jets. it's ust my own method on certain carbs which will now be changing due to the sourcing of an ultrasonic unit with many thanks to a company who is helping with a restoration setup I'm sorting out.

 

ed

HenryB Wed, 11/07/2012

Hi,

Got my suffolk running a bit healthier now, i over filled the sump a fair bit and oil was ending up in the cylinder, havent checked the choke problem yet because i have a new problem, when i turn the fuel on petrol starts pouring out of the air intake and various other places, and it is literally pouring, not dripping. i dont know what to do about this, so i have come back here for advice.