Briggs 31c707 17.5HP on Craftsman LT2000

[ILENGINE]

giving indications that it isn't getting enough fuel to sustain high speed operation. Which without a load would still be the idle circuit in the carb. Which is what that mixture adjustment screw should assist. You said it doesn't seem to do anything so that could be part of the issue. Also any old fuel residue in the main jet can cause similar issues.

 

[bertsmobile1]

As you have other gear around, rig up a temporary tank, a small push mower one will be fine and with some new fuel line connect it directly to the carb
Old fuel lines go soft inside and collapse blocking off the fuel line
Debris accumulates in the fuel tank then organic bits like glass clippings adsorb the petrol which displaces the water & turns them transparent and thye will also get sucked down the fuel line like hair in the shower outlet .

 

[Tinkerer200]

Some of this series engine had voltage regulators, not all. I can send you a Service Manual for your engine IF you like, address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com

 

[SpareUsTheCutter]

As you have other gear around,

... you guessed it!!

actually, the fuel tank is near empty, although enough fuel to run, lines SEEM clear on inspection, but will certainly look further into this and try with a decent amount of fuel in the tank

 

[SpareUsTheCutter]

. I can send you a Service Manual for your engine IF you like,

Yes please, that would be fantastic, I've pm'd you my email

 

[SpareUsTheCutter]

giving indications that it isn't getting enough fuel to sustain high speed operation. Which without a load would still be the idle circuit in the carb. Which is what that mixture adjustment screw should assist. You said it doesn't seem to do anything so that could be part of the issue. Also any old fuel residue in the main jet can cause similar issues.

Conversely, it seems to be USING more fuel than it should... not very scientific but i recall giving it a good amount, maybe a gallon and a half when i first got it. My other half tried to mow with it for about an hour, before reporting to me that it runs like a bag of <<bleep>>. Since then, I've run it a few times to get it up to temp.. maybe 5 minutes max, twice dumped fuel out of carb and lines... doesn't seem like it should be near empty yet!

As for the mixture screw, I haven't attempted to remove it and inspect since it has the "anti-tamper" plastic surround, but a this stage I figure I have little to lose and might just have to dig in there!

 

[SpareUsTheCutter]

just reporting back... so it turns out the float bowl seal had perished - which means: 1. a definite cause of fuel loss, leading to me thinking it was "using" more fuel than it should 2. possibly has a bearing on fuel delivery too.. although... I also had a close look at the fuel filter, which is a generic replacement - happens to be hard to see through the plastic casing, but i noticed a definite piece of crud in there, so took a hacksaw to it - doesn't look too bad apart from the afore-mentioned bit of filth, but then on closer inspection I can see it's dark at one end, i.e. tiny bits of debris have accumulated.
Genuine Briggs filter on order and hope to pick up a float bowl gasket at my local shop (crazy prices for the genuine ones online - I mean crazy for a piece of rubber anyway!). New fuel lines and a clean-up of the tank and I'll see if things improve.