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ZippoVarga

Technical Question about B&S carbs

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ZippoVarga
Ok......here's the dill pickle. I've come accross this a number of times and I always look at the float. Perhaps it's something else? The engine hydro locks because of fuel getting into it. It drains into the crank case as well as hydro locking. IS this the needle and seat not doing it's job? Is it the float not doing it's job? OR is it something I have not considered. Looking forward to the technical bullitins on this one. I fix em easy enough with fuel shut off's but obviously there's something at play that's causing this. HELP!! Sean

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D-17_Dave
I don't think you can hydro lock a horizontall Briggs due to the updraft carb. And by your profile you show to have vertical shaft engines so thats what I'll address. Either the float has a hole in it, is not adjusted correctly, the seat is improperly installed or has trash in it so it can't stop the flow, or the carb is incorrectly assembled allowing the gas to seap out of the bowl improperly. Most of the time I see the carb seat not cleaned leaveing trash in the seat area or the seat not installed correctly due to the carb. being swapped and the wrong carb. kit being installed. This case would apply when the wrong seat is supplied for the wrong carb. Since Briggs used 2 different types of seats. 1 being the rubber seat w/ a solid needle, 2 being the solid seat and the rubber tipped needle.

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HubbardRA
Dave, I had a Murray with an 11 Hp B/S vertical shaft that used to do that. I would take the carb apart and everything appeared fine. It may mow fine for a month, then suddenly the leak would appear. I tore into the carb three different times. Along with that, the oil got changed because of gas in the crankcase. The last time it did that was while I was mowing the lawn with it. Hard to find an intermittent problem when nothing appears wrong when you disassemble the carb, and it may only happen every month or two. Problem with those carburator setups is the location of the crankcase vent hose attachment. If the float needle leaks at all, the fuel will build up in the carb and run into the crankcase. If the crankcase is full of fuel, the piston cannot go down and the engine will not turn over. Needless to say, that tractor eventually went to the local dump in pieces. Problem cured - nothing being used at my place now other than Simp and AC large frame tractors, with horizontal shaft, cast iron engines. I'd rather have one leak on the ground, than into the crankcase.:D:D

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Jovee
Does this happen while parked for a time or while running/trying to start? If its parked, see Daves explanation above. There can be no other reason. If running does it smoke bad or run like theres too much fuel? The intake valve guide could be gummed and its not allowing the valve to shut all the way and dumping excess fuel wherever it can (crankcase)

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ZippoVarga
I have only seen this happen on late model vertical shaft Briggs. And as far as the needle and seat being correct.....they are opposing rubber and non ferrous metals. I clean, inspect the needle and seat to no avail. On occasion the leak corrects it self but returns. I keep my fuel cans closed and strain the sediment from the tanks when ever I notice any. Is this a common problem with the verticle briggs? Dave, both my serf and broadmoor have verticle and I have never had a float or needle problem with them. It seems it only happens to the later model briggs engines. The simple fix is a shut off. But my main inquiry is to the integrity of these later model briggs carbs. Free is free and a shut off cures the ailment BUT...Just looking for a reason why this happens. I've seen it all too often and I am looking for a solution. The particular engine's i'm refering to right now are a pair of 283707's. One on a Simplicity RTG and the other on a JD 111. The date codes put each engine within two years of manufacture and both have this affliction along with the 11.5 previously mentioned. That's three engines with the same problem from three different owners all manufactured with in a three year span. Do we have an overly sensitive briggs carb set up in this time frame? Or is this a broader problem spanning more than the three years of these particular engines?

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D-17_Dave
I personally think it's a weak point in the Briggs carbs. Still , there are a few variables to ponder. Kohlers and Onans use fuel pumps for the most part so their needle design must withstand the pump pressure so I think they are a little stronger. Briggs uses a small keeper spring to pull the needle open just in case it gets stuck shut from evaporated fuel. This spring if deformed or installed incorrectly could possibly hang the needle open. Or anything could be out of adjustment and hold it open. Like a piece of deformed bowl gasket. Last, as someone else mentioned in an older post, if the jet isn't screwed in all the way it could let gas seep by into the carb throught. I normaly test the needle with sme carb cleaner by adjusting the float, turning it upright, then squirting in some cleaner. It won't take long to see it seep if it's leaking. I've also adjusted it a little hight(inverted) so the float cuts the fuel off a little sooner. When installing either seat style it's important to get ALL of the old seat out and use something small and smooth to fully press in the new seat as fuel could leak around it effectively bypassing the needle. These are some observations I've seen over the years. Sometimes I find the problem, sometimes I guese takeing it apart enough times it gives up and corrects itself. Sometimes I give up because it's running too good and I just use the cutoff. Your results may vary.

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MrSteele
I have used several of the late model vertical shaft Briggs engines, BUT, I always use a fuel shut off valve when not using the engine. Many engines have been ruined because not everyone checks the oiil before starting after the engine has been idle for a few days. Apparently, this is a design flaw in the carbs, or is simply a design to sell more engines? I always shut the gas off, and anyone with an engine, no matter what kind, with a gravity feed to the carb, should do so, as well. I have had Kohlers do the same thing.

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Jovee
Zippo, The float is gunk free I assume? Nothing to weigh it down? Funny you mention the White/MTD though. The make would have nothing to do with it but the last two I worked on with that problem were from those manufacturers. Both cases the float was defective. One with an obvious internal leak and the other not so obvious but was there. Bad batch of floats???

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ZippoVarga
Dave Steele and Jovee, Thanks a bunch for all your inputs. I too use shut off's on ALL my engines and always let the bowl run out with the gas shut off. I agree that the gravity fed machines seem to do this more often than the fuel pump units. As with a JD110 I worked on not too long ago with a briggs and one of those magnet operated fuel pumps. Only it's problem was the pump not delivering the fuel because of a pin hole in the diaphram in the pump. The JD111, Simp RTG and White all now have fuel shut off's on them and the owners have been instructed to ALWAYS check the oil prior to starting and if it's over full then they need to call me before trying to start them. I had already gone through the carbs on each and as was mentioned earlier........nothing jumped out as being unusual or out of the ordinary. To comment on the floats. Two of the three are the plastic type and neither has the helper spring. I am familiar with this spring and I thought it was odd that neither of them had it in pace. The third one has the old brass style with the helper spring in place. Thanks again every one for an insightful discussion about the vertical shaft carb problems we all seem to have had. I am heading out this minute to check all three for a loose jet screw as was mentioned by Dave. Thanks again!!!! Sean

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ZippoVarga
MPH!!!!!!!!!! YOU SINGLE HANDEDLY SOLVED MY PROBLEM!!!!!!!! I knew the engines looked funny, so i set them up right and voila!!!! NO MORE LEAKY CARBS!! Now.....how do i get the things to start??????????? :-)

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Jovee
quote:
Originally posted by ZippoVarga
MPH!!!!!!!!!! YOU SINGLE HANDEDLY SOLVED MY PROBLEM!!!!!!!! I knew the engines looked funny, so i set them up right and voila!!!! NO MORE LEAKY CARBS!! Now.....how do i get the things to start??????????? :-)
:D:D:D:D:D:D

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Guest
I have a Briggs 18.5 HP engine that has never ran right since new. It has always lopped or galloped and drains gas into the oil pan. Anyone have a fix for the problem?

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ZippoVarga
How do you adjust a float that's plastic? A longer needle? Heat the float and manipulate the saddle where the needle rests in the float? Just an obvious question that popped into my mind with these throw away briggs carbs.

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