Groundsmaster 52 runs 10 minutes, then dies

[piper184]

Great post. However this only works if the pulse line does not have a loop that can cause oil to collect in the pulse line. The pulse line must NOT have a loop between the pump and the pulse port. In other words, the pulse line MUST be all down hill from the pump.

Correct. A loop really messes things up if fluid gets in it. In my case the pump is below the engine so it is possible for crankcase fumes (2 stroke) to condense in the line and flow to the pump. The weep hole at the bottom of the pump takes care of that and the fuel tank is below the pump so it has to earn it's keep! Also Rotax (aircraft engine) says NO Ethanol, ever! Plus it likes 91 octane. Fortunately that is available.

I will second the comment about the condenser might be bad even though it is new. I have seen out of the box failures before. Same goes for fuel pumps. Ever open a box of nuts to fine one or more that don't have any threads inside? Stuff Happens...

 

[Volvoman]

Great post. However this only works if the pulse line does not have a loop that can cause oil to collect in the pulse line. The pulse line must NOT have a loop between the pump and the pulse port. In other words, the pulse line MUST be all down hill from the pump.

On the Groundsmaster 52, the pulse line is looped around the dipstick tube. This is how it is supposed to be positioned. Evidently the pulse vacuum is unaffected by any accumulation of oil in the loop.

 

[Tony H]

Looking at other downdraft carburetors, it appears that the Seat IS metal and it can be unscrewed out of the carb, when carb is disassembled. I'm still leaning toward a reduced diameter in a jet or Seat.
Was this a sudden issue or did it start after the machine sat for months? I don't remember if you mentioned the scenario.

 

[Volvoman]

Looking at other downdraft carburetors, it appears that the Seat IS metal and it can be unscrewed out of the carb, when carb is disassembled. I'm still leaning toward a reduced diameter in a jet or Seat.
Was this a sudden issue or did it start after the machine sat for months? I don't remember if you mentioned the scenario.

The problem arose suddenly. No advance warning. Unless the seat is pot metal gray, the usual brass screw-in seat wasn’t there. I looked specifically for it and wondered at the time I had it apart about why there wasn’t any. Well, it’s coming apart again in a few days when the kit arrives. Will post about it’s presence or absence when I’m in there. I can’t image it running well at all without a seat tho, as machining the carb body to simulate an insert seat would be difficult if not nearly impossible. The reduced diameter of a jet is very plausible. The kit contains a new high speed jet, so will see how it all pans out once back together.

 

[MossRoad]

The problem arose suddenly. No advance warning. Unless the seat is pot metal gray, the usual brass screw-in seat wasn’t there. I looked specifically for it and wondered at the time I had it apart about why there wasn’t any. Well, it’s coming apart again in a few days when the kit arrives. Will post about it’s presence or absence when I’m in there. I can’t image it running well at all without a seat tho, as machining the carb body to simulate an insert seat would be difficult if not nearly impossible. The reduced diameter of a jet is very plausible. The kit contains a new high speed jet, so will see how it all pans out once back together.

How much was the price of the kit VS a whole new carb? Just asking, because many moons ago I used to rebuild automobile carbs fairly often. However, with small engines these days, like chainsaws and weed eaters, a new carb is almost always just a couple bucks more than a rebuild kit.

I know your unit is older. But I was just curious.

 

[JBF43]

It isn't uncommon to have an engine run poorly,not start or intermittently run rough after a routine tune up,becasue new condenser is bad.

Have had this very thing happen in the past with auto tune-ups. Replaced points, plugs, and condenser just because it was time/ mileage. Engine ran on the old parts but wouldn't start after the tune-up. Put the old condenser back in and it cranked right up with the other new parts still in it. Just a possibility.

 

[Tony H]

The problem arose suddenly. No advance warning. Unless the seat is pot metal gray, the usual brass screw-in seat wasn’t there. I looked specifically for it and wondered at the time I had it apart about why there wasn’t any. Well, it’s coming apart again in a few days when the kit arrives. Will post about it’s presence or absence when I’m in there. I can’t image it running well at all without a seat tho, as machining the carb body to simulate an insert seat would be difficult if not nearly impossible. The reduced diameter of a jet is very plausible. The kit contains a new high speed jet, so will see how it all pans out once back together.

VERY curious what you find. Your issue is driving me crazy. You obviously know your way around an engine.
As you can tell from my posts, I'm leaning toward fuel. If it was ignition, I think it would be breaking up as you idled up, not just BOG down. Do you have Welding Tip cleaners that you can put thru the jets to see if something pushes out onto a paper towel?

 

[Volvoman]

How much was the price of the kit VS a whole new carb? Just asking, because many moons ago I used to rebuild automobile carbs fairly often. However, with small engines these days, like chainsaws and weed eaters, a new carb is almost always just a couple bucks more than a rebuild kit.

I know your unit is older. But I was just curious.

I paid $35 including postage for an OEM Briggs. I didn’t check on a new carb for it, as I have gone that route before for some much smaller engines and found the quality was unpredictable. Sometimes good, sometimes not. This carb is made to be rebuilt, so thought it best to go with the known high quality OEM Briggs parts. What I got had been on someone’s shelf for quite some time, no doubt, but it shouldn’t make any difference provided any rubber or vinyl parts are okay.

 

[MossRoad]

I paid $35 including postage for an OEM Briggs. I didn’t check on a new carb for it, as I have gone that route before for some much smaller engines and found the quality was unpredictable. Sometimes good, sometimes not. This carb is made to be rebuilt, so thought it best to go with the known high quality OEM Briggs parts. What I got had been on someone’s shelf for quite some time, no doubt, but it shouldn’t make any difference provided any rubber or vinyl parts are okay.

Thanks!

 

[Richard001]

On the Groundsmaster 52, the pulse line is looped around the dipstick tube. This is how it is supposed to be positioned. Evidently the pulse vacuum is unaffected by any accumulation of oil in the loop.

And you know this how ?

Have you checked the pulse line to see if there is oil in it ?