"ok i got v twin briggs 16 hp.modle is 42a707" "Well first off, a 42A707 is not a "V" twin." "i have rechecked the number this is a twin engine.it has 2 pistons." When you post description of your engine, you need to be accurate to get accurate info. Your engine IS NOT A V TWIN!There are distinct differences in engine, not every twin is a V Twin. You may need to set the governor static setting, Service Manual I sent the link to should help. Walt Conner

If it was me I would do complete fuel system clean up. Said this before with that many hours and years on it your fuel system is dirty and about to fail. I would Start at the tank. remove it, clean it out either by swabbing or pressure washing. rinse with gas or alky. Next I would replace all the fuel hoses, fuel filter, install shut off valve, replace the hoses after the fuel pump and the fuel pump vaccum hose. If you don't want to clean the carb. bowl and spray the main jet with carb. cleaner add some fuel system cleaner when you get it filled back up with fresh gas and clean system up to the carb. Also while I was in there I would also inspect the elect harness, switches, looking for loose hanging wires, chafed wires, rusty connections. plastic tie wrap any loose wiring that could get chafed or rubbed against moving parts. If you want it to last you need to do this very few years 6 is pressing it, but not bad depending on conditions you work your equipment in. I would also make sure I check the air filter often older vanguard are fussy with the small air filter between the cylinders. Now cylinders reminds me of cooling fins. have you checked them lately? Might want to revisit the owners manual on pre-ventive maintenance make sure you got all the bases covered. do that and that tractor may last life time???? another thing if you going by the 50 hour oil changes you better be mowing in dust free invoriment?? if not then 50 hours between oil changes is way too long hence extreme conditions in the owner maintenance schedule??

Inspect the gas cap carefully. Some OEMs don't put a vent "hole" in the top of the cap. Some caps have the venting passages in the threaded area on the underside of cap. I have not ever seen a gasoline powered LT or GT that had an independant "vent hose" or "vent plug" (but I have not come in contact with every machine ever made either). The vent provision is usually incorporated into the cap because it is simple and does what it does reliably (until it clogs). In regard to your concern about the amount of fuel visible in the transparent fuel filter. The "empty" head space above the liquid gasoline IS NOT atmospheric air! It is a "head" of vapor that results from some of the volatiles in the gasoline evaporating. As these "fumes" or vapors are evaporating from the liquid they rise. Not being able to escape (because the filter and fuel hoses "retain" them), they instead form a "pressure head" which exerts enough force to displace a portion of the fuel back into the tank. Having said all that, you can't use the presence of "empty space" in the filter as evidence of fuel starvation. ALL gasoline filters will have some "empty space", even the opaque metal kind, it is a trait of the gasoline at average ambient temps. Your problem certainly sounds like a clogged fuel tank vent. Or you could have some "loose solids" in the tank that are moving around with the fuel to be caught against the tank outlet hole. Another possibility is engine overheating (due to debris or "mice nests" in the cooling fan shrouds. Try deerslayer's recommendation about running with the cap off (or just very loose). If you run it til it acts up and then loosen the cap, the engine should straighten up and act right if it was being denied a vent.

Well, time for the "off the wall" suggestions I guess? :-) Push rods- Is the compression "bump" on the intake valve? IF SO, maybe the steel push rod doesn't expand enough with the heat, (compared to the barrel) resulting in an effective increase in valve lash? Aluminum expands about twice as much per degree as steel. I think that's an avenue worth pursuing. It might be only a few thou difference, but it might be enough. IF that doesn't do it, I swap the starter, unless he's "literate" with a voltmeter. In that case, I'd check for VOLTAGE DROP across the various connections to look for an obvious trouble spots. I'd divide the circuit into 3 sections- 1 Battery + POST to + starter motor POST. 2. Starter motor POST to starter motor CASE. 3. Starter motor CASE to battery - POST. Check voltages with the engine cranking. A "perfect" reading (doesn't exist) would be 0 volts drop. If any (one of three) circuit is excessive, one can then narrow that part of the circuit to its smaller parts. Example circuit 1- Battery post to cable connector, to cable, to connector, (on other end of cable) to solenoid stud, to other solenoid stud, to starter motor stud. Typically, you'll have a lot of small voltage drops (one at each "junction") that adds up to a more substantial total drop. Circuit# 1 tests + side 2 tests the motor 3 tests the ground side. Also make sure starter is well grounded to the block. Am I rambling yet? :-)