Engine problems on Briggs and Stratton

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BostonInbred

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Re: Engine problems on Briggs and Stratton
« Reply #15 on: March 10, 2010, 23:36 »
Hi Gwiz

I still think it is a fuel problem because it will fire but not run. I just do not know enough about carburetors (yet) to solve it. There is some info from other that says that engines that will start but not run often have a root cause of a faulty diaphram. Cant find one of these in my carb but will see what info I can find on the net. My symptoms are just those of a faulty diaphram.

Thanks for your help

Kind regards

Andrew

Small engine carburetters are simple, because theres almost no moving parts. Replace the rubber diaphragm and the gasket. If that doest work, then its either not the carb or the carb is furred up in the fine channels.  You can try totally dismantling the carb and using  steel wound guitar string as a fine cleaning reamer, and cleaning out the channels  that way. The diaphragm usually incorporate two flap valves so the failure of the diaphragm generally kills the engine stone dead apart from a few seconds running. You will have to strip it down totally really, clean it all and reassemble, theres never any point in half doing it.

Another strategy is substitution, if you have another carb you''re reasonable sure works ok. New carbs are a silly price - like 100, which is uneconomic.

It does sound like fuel starvation. The only other possibility is the fuel feed - airlock, or vacuum in tank  holding the fuel back.


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Andrew Burrow

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Re: Engine problems on Briggs and Stratton
« Reply #16 on: March 11, 2010, 08:43 »
Dear Gwiz,

I took the carb apart the other day but perhaps not fully. I did not see a diaphram, so I need to do this again more fully. Thanks for your comprensive comments and the thought on substitution.

Kind regards

Andrew

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R Tallentire

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Re: Engine problems on Briggs and Stratton
« Reply #17 on: March 11, 2010, 20:05 »
Hello Andrew
In your first posting you quoted the model as 80832. That makes it a 3hp vertical crankshaft engine with a flo-jet carburettor. If so it wont have a diaphragm or fuel pump as the tank is above the carb. The flo-jet is a bit of a pig to service as the lowest point  for fuel is the space between the jet tube and the adjustment needle. Any water gathers there and corrodes the threads in the casting so the needle wont screw in, and the jet wont screw out for servicing. You are supposed to remove the jet tube to split the carb if you want to get at the float chamber etc. but you can usually wiggle it apart especially if the jet is loosened a turn or two. Blow everything out with an air line and, if the jet will screw out, you can initially set the needle by  screwing it right in, not too tight or you will mark the needle,  then screwing out 1.5 turns. Final setting is by  setting the throttle at half revs and screwing in until the revs drop, then out until the revs drop then back to halfway in between. The pilot jet is then set in the same way with the throttle on fast tickover.. If the jet didnt come out, the needle wont screw right in so initial setting is guesswork.
One other thing, the symptoms of a dying B & S coil is poor starting, followed by running for a minute or two then stopping.
Regards, Richard
R Tallentire

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Andrew Burrow

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Re: Engine problems on Briggs and Stratton
« Reply #18 on: March 12, 2010, 11:43 »
Dear Richard,

You certainly know your Briggs and Stratton. Your description of my engine and carb is spot on. I will try once again on the carb, but I have pretty much done everything you said. Remarkably, I had no problem getting the jet or needle valve to move. Your idea on the coil maybe a step forward. Would I get one from Briggs and Stratton? Their web site does not even recognise my model number.

Kind regards

Andrew

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R Tallentire

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Re: Engine problems on Briggs and Stratton
« Reply #19 on: March 13, 2010, 19:28 »
Dear Andrew
I am more used to the horizontal crankshaft versions of the side valve B & S engines but the magneto coils are the same. Coils are fairly expensive so be sure the fault is definitely  not the carb or plug before buying a new coil.
Some early 3hp engines had a three pole mag and I dont think these are compatible with the two pole type but if you have a two pole mag, replace it with the contactless magnetron type, prices are much the same and you wont have to worry about points needing cleaning after a lay up.  Any local Briggs & Stratton agent can supply the right coil.
Regards, Richard

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Andrew Burrow

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Re: Engine problems on Briggs and Stratton
« Reply #20 on: March 14, 2010, 17:34 »
Dear Richard, GWIZ and all,

I now have a fully functioning engine on my rotavator.  I am sure that it was junk in the carb, fuel line etc. I cleaned the carb and tank replaced the fuel line that was perishing on the inside causing a black dust etc. But the thing that finally got it started was Richard's advice that the needle valve should be opened 1.5 turns to get an initial start up. The manual said 1/2 to 3/4 and it would fire once and stop. When openned to 1.5 times it almost ran. On 2 times it ran and i could tune it. It now runs better than it ever did.

Many thanks to all.

Kind regards

Andrew Burrow



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