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Farm Pumper, or not Pumper

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Old 06-08-2019, 11:55:25 PM
muzzery muzzery is offline
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Default Farm Pumper, or not Pumper

Hi all. I’m having a crack at starting this old girl. Still nothing. The only thing pumping is my heart huff puff! It will fire if I close the valve gap, practically advancing the exhaust valve timing, so you can see it flaming out the exhaust. It makes me wonder if there is too much compression, for the old school spark plug? I did have it resleeved and there’s pretty good compression when you turn her over. I can’t see what else could be wrong. It has run once for about 15 seconds so I reckon timing is right.( spark mark on flywheel is showing correct position)
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Old 06-09-2019, 12:20:59 AM
Rusty Engines Rusty Engines is offline
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Default Re: Farm pumper . Or not pumper.

flaming out the exhaust???
Is the exhaust port at the bottom of the stroke not blocked as that is the main exhaust outlet

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Old 06-09-2019, 12:35:52 AM
muzzery muzzery is offline
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Default Re: Farm pumper . Or not pumper.

No, it’s functional. The flame out happens at the start of power stroke- if the valve is advanced to open early. Back the valve timing off to normal, and nothing fires at all.
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Old 06-09-2019, 01:07:39 AM
Scotty 2 Scotty 2 is offline
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Default Re: Farm pumper . Or not pumper.

Hello Muzz
Back to the beginning and check everything from governor operation/setting to timing and everything in the middle. I did have trouble with a pumper because the governor was set too light. It was wanting to miss with the cranking speed.

Cheers Scott
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Old 06-09-2019, 01:50:33 AM
cobbadog cobbadog is offline
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Default Re: Farm pumper . Or not pumper.

Back to the basic s for sure. These can be fun to get right but once running right they go for ever, As Scotty suggested try increasing the governor to make it run faster so that more fuel is getting in or pour a bit of fuel down the plug hole to see what happens.
Ignition timing is important so check it again and leave your valve clearance open as they are not normally that close.
Check for a good spark and that the plug is firing or use a known good plug to eliminate a dodgy plug.
Mine was one of those engines that wouls start only when it wanted to. You could start it a 100 times at home hot or cold and take it out and it would not fire. Turned out the magneto needed charging up and now it starts anytime and anywhere.
Persist, you will win.
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Old 06-09-2019, 02:35:20 AM
eddie bedwell eddie bedwell is offline
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Default Re: Farm pumper . Or not pumper.

Hi Team,
link is to the F & J farm pumper operators book

Page 11 tells where the exhaust valve should open and close at.

If your suspect spark plug or the magneto power is at fault, in my experience if the magneto fires each time the piston comes near TDC a faulty plug or weak magneto will fire the residual mixture on the off (non compression) stroke and give results such as you are seeing--if the engine had a timed mechanical inlet valve it would tend to backfire out of the inlet/carby.

With an atmospheric or automatic inlet vale it would not fire out the inlet as the pressure rise from firing would help keep the inlet valve closed and so would backfire out the exhaust, especially if you have closed up the valve clearance so that the
exhaust valve would tend to be open after TDC.

Generally with older engines the valve clearance is adjusted to get the valve opening and closing positions correct for best running.

The faulty spark plug can fire under less compression, as you have said--you may get some success if you closed the plug gap down to say around 0.010" to 0.014" and see what happens as this tends to lessen the load on a tired maggie and sad plug.

A weak sparking magneto can be fooled into starting an engine if you rub a soft black lead pencil carbon onto the plug electrode gap--you will get one or two sparkly sparks that can fire the engine off and get enough speed up for the maggie to continue firing the plug--works most times in my experience--your mileage may vary.
Eddie B.
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