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Collection, Preservation and Display of Old Lawn Mowers

Starts and Runs but stalls

Hi, so the Webb is back together and I thought I'd mow the lawn, as you do...

Fires up and Runs first time from cold and mows OK for a bit then just stalls, I thought it was the grass catching up between the knife and the cylinder so I gave up and cleaned it down. Whilst "driving" it back it continued to stall... I'm thinking fuel starvation possibly but then it will start first pull after its stalled. 

Any pointers to what it could be? 

It actually mowed for longer on half revs and stalled less than when it was on full revs. 

Forums

wristpin Sun, 02/10/2016

May be some restriction in the fuel supply not supplying enough for higher engine revs.  Get a glass jar and pull the fuel pipe off where it enters the carburettor. Observe the flow which should be undiminished for thirty seconds. If it slows, check the tank cap vent.

Then report back!

wristpin Sun, 02/10/2016

You should feel a lump when you pull it over. If the valve clearances are very tight they may close completely when hot but that doesn't fit an immediate restart.

Webb17 Sun, 02/10/2016

OK you can Def feel the compression and I measured it at 70psi rising to 100 with a squirt of oil. 

wristpin Mon, 03/10/2016

No logic in it but just check the valve clearances cold. Did you tell us what engine you have but assuming that its the Suffolk  A114 they should be 10 thou exh and 6 inlet but some clearance on each should eliminate clearances being the cause of your problem.

 

Webb17 Mon, 03/10/2016

OK will do next time I'm in the workshop. One thing I thought was is there any adjustment to be had on the guvnor? I guess if this didn't respond adequately to demand that would cause a stall?

wristpin Mon, 03/10/2016

Possible, but unlikely to be a governor issue so would advise against fiddling with it.

If it has the A114, the governor arm fits to flats on the shaft emerging from the governor mechanism within the crankcase so there's no adjustment there. There may be alternative anchorage holes for the governor spring and from memory there is a knurled adjusting knob threaded to the vertical rod to allow some adjustment of the top no load speed. If you feel compelled to try altering the spring position, make a note / take an image of where it was before you started so that it may be returned to the original setting.

Going back to your comment that it was less likely to stall when working  lightly than under heavier loads it is possibly pointing to a weak mixture so as you have already checked the fuel supply, a thorough clean of the carburettor may not be time wasted. However, memory suggests that in this application the slow running mixture screw of the Dellorto carburettor is hidden behind a blanking plug to discourage tampering; so before stripping and cleaning  It may be worth removing this plug and "playing " with that adjuster. Although nominally the slow running adjuster, it does supply a small amount of fuel to assist the main jet or emulsion tube  in delivering the required mixture for full load operation. 

 

Webb17 Tue, 04/10/2016

I think a fiddle with that gnurled nut may be the way  forward as I did adjust that before!  Reason being that the Mower wouldn't shut off with the throttle alone, it had to be flooded with the choke.  so I adjusted it so that the throttle arm went back fully and shut down. I'll put this back to where it was and see if that improves.

Webb17 Tue, 04/10/2016

I think a fiddle with that gnurled nut may be the way  forward as I did adjust that before!  Reason being that the Mower wouldn't shut off with the throttle alone, it had to be flooded with the choke.  so I adjusted it so that the throttle arm went back fully and shut down. I'll put this back to where it was and see if that improves.

Webb17 Tue, 04/10/2016

I think a fiddle with that gnurled nut may be the way  forward as I did adjust that before!  Reason being that the Mower wouldn't shut off with the throttle alone, it had to be flooded with the choke.  so I adjusted it so that the throttle arm went back fully and shut down. I'll put this back to where it was and see if that improves.

wristpin Tue, 04/10/2016

Yes, yes ,yes we get the point! Multiple posts not required!!

Just  to make it clear, the engine should not shut down on the "throttle" per say but the final movement of the handle bar lever should allow the lever at the other end of the cable to contact a switch and Earth out the ignition. The throttle stop screw on the carburettor should hold the throttle just open enough to obtain tick over rpm - probably around 1600 rpm.

Webb17 Tue, 04/10/2016

That wasn't me !  That was the computer....  I don't think I have an off switch? any clues where I might see this. On the handle bars all I have are the two chrome levers one  that drives the Mower and cylinder and the other one  disengages the roller/drive but keeps the cylinder spinning..

will re adjust the guvnor to where it was then go from there. 

wristpin Tue, 04/10/2016

On the vertical plate that carries all the throttle and governor gubbins ( technical term) you should see a wire going to a terminal. With the throttle lever on the handlebars in the fully closed position that terminal should be contacted by a lever which earths it out and cuts out the ignition. If your machine has a black plastic rotary  throttle lever it should have a click (detent)  between slow run and off but they were prone to loosing their click  and shutting down rather than ticking over.

Webb17 Sun, 09/10/2016

I found the cable and switch but it doesn't work. I shorted switch against body but still didn't work so must be problem further up line. Any clues?
Adjusting the guvnor has made running OK now, it doesn't stall. Spark is pretty weak so I'm going to chuck a new plug in. What does it take and are there any adjustments/cleaning to points to be made to create bigger spark?

Where can get a new fuel tank or replacement weld on neck and cap?

wristpin Sun, 09/10/2016

When you say that shorting the cable terminal to earth (an unpainted surface) "does not work",  are you saying that it does not stop the engine? If so it suggests a break in the wire between the switch terminal and the ignition coil. I would expect your machine to have electronic ignition so no contact breaker points. If the engine is running OK the spark is good enough!

To check out the kill wire you will have to remove the flywheel .

There must be plenty of used fuel tanks around but it surprises me that yours is steel and not plastic - again, posting some images will help your cause as those of us trying to help you are working blind!

Webb17 Mon, 10/10/2016

Thanks for the reply, 

Yes I mean the Mower won't stop when I short it out against another bit of body.  I attach a pic of it when it was stripped down. It has a metal fuel tank but I inherited the Mower so maybe it was changed?...

Webb17 Mon, 10/10/2016

I've tried to post a pic of the Mower.... Maybe it takes a few minutes to come up?

wristpin Mon, 10/10/2016

Looks like it's the model based on the Atco Commodore. That will have electronic ignition so no contact breaker points but if you want to investigate the non functioning kill wire you will have to remove the flywheel. No sign of the fuel tank so difficult to comment on it!

A couple of wider angle in focus images will help.

 

 

hortimech Mon, 10/10/2016

the tank is bolted to the handles where they cross and yes, it is a 'badge engineered' Atco. Finding a tank may be a bit hard, try the well known web site. You could try to repair it, either by brazing or by soldering it, but either way, make sure you wash it out well, before going anywhere near it with a naked flame, for obvious reasons.