314-A running too lean

[GeoPeg 0]

OK, here’s the problem. My 14hp K321S Kohler engine runs (I believe) very lean after a couple of minutes, popping loudly while running, loses power, slow acceleration - carb adjustments make no difference. Here’s what I have done and the result. Cleaned the tank thoroughly including the small outlet screen inside the tank – verified the fuel shutoff valve on the tank is wide open – replaced the fuel cap with a new one (venting is good) - replaced all rubber fuel lines with new hose and clamps from the tank to the filter to the pump, to the carb – replaced the fuel filter (see-thru filter) – removed the fuel pump, checked by hand, seems ok – replaced fuel pump and cranked engine, fuel output was not nearly as much as when the pump was activated by hand, but “seemed adequateâ€. Replaced air filter for good measure. Other than attempting to adjust the hi-speed mixture, nothing else done to carb. The problem is still there. In some form or fashion this has been going on for a long time – previously found much debris in the tank, cleaning that out fixed the problem (for the rest of the season). It has always been slow to start cuz it had to suck gas all the way from the tank, as if the carb bowl and all the lines dried up over a 2-3 day period. The solution I used was to briefly pressurize the tank enough to push gas up to the carb – then its starts almost immediately (2^nd revolution)!!! Now when I have been mowing for a while and look at the fuel filter, it’s almost completely out of gas – I can’t even imagine how the engine is still running – re-pressurize the tank and the filter fills back up – good for a while, then it happens again. When the filter is almost empty, I can disconnect the output line and there is no gas flow – re-pressurize and fill the filter and I have constant gas flow, more than enough to satisfy this gas guzzler – it’s as if the gas line has an air lock. I have checked for leaks in the fuel line everywhere – nothing. Checked fuel filter in correct direction – it’s OK. Update - Now, even when the filter is full, it is still popping and losing power. So what’s going on? Bad pump or carb? How can either one suck the gas out of my filter with little to no gas flow remaining?

[boovuc 1,090]

I would look at a bad pump first. Here is what I would do but it involves another tank. I have a spare tank from a small push mower. If you can lay hands on anything that SAFELY holds gasoline using a fuel valve and a fuel line hooked up to your carb, get a helper and just hold a fuel tank with gasoline above the level of the carb and start it. It may require adjusting the carburetor but see if a good simple gravity flow of gasoline into that carb cures the issues. If it does, you have a fuel delivery problem and most likely its the fuel pump based on what else you have tried.

[GeoPeg 0]

Well that just sounds like a good idea and I just happened to have a spare fuel tank from a push mower and some spare (new) fuel hose, so that is exactly what I'll try!

[GeoPeg 0]

Dang! Threw the old tank away! I'll come up with something else.

 

In the meantime, here's an interesting side note to the carburetor adjustment for the “26†and “30†carbs. The instructions say to adjust the main jet needle by turning (clockwise) in until the engine slows (running too lean), then note the position, then turn out until the engine slows again (too rich), then set halfway between. The interesting thing to me is that there is a governor fighting to maintain a constant engine speed while you are doing this. Seems like a less than refined approach to practically cut off the fuel supply on one end and drown it on the other end. Would you think that manually holding the governor/throttle linkage in one position while you make the adjustment might give a better result?

[boovuc 1,090]

LOL.....I know what you mean but normally the governor will start to cycle the engine up and down when you get to the extreme limit of the adjustment. (Rich to Lean). The idea is to get it somewhere in the middle and even that is speculative unless the engine is at operating temp and most of the time, when you are doing this adjustment, it isn't!

[GeoPeg 0]

I thought I would follow up with the resolution – first, the fuel tank trick made no difference. Next I added an electric fuel pump (I wanted to solve the priming issue) and bypassed the mechanical pump – that of course, made no difference – then I took the carb apart and did a rebuild – I found an amazing amount of debris in the bowl, but the rebuild made little difference and the neighbors still looked at me funny when the engine started popping and backfiring – problem not solved. So to quote Brian Miller, “Most carburetor problems are electrical.†The meaning of course is to check the ignition system. And sure enough I discovered an untouched set of points, condenser and plug … for the last 14 years! What a rookie move!! The points were incredibly pitted and barely opening – the plug had a gap of (est’d) 35-40 thousandths plus a strange collection of black powdery stuff of one side and a feathered, yellowish-white collection on the other side. And the condenser’s electrical wire was cracked from age. New parts were installed and now the engine runs like new – amazingly strong – I had forgotten how much power it has – and of course, no backfiring. The hardest part was setting the points since I had no easy way to physically rotate the engine by hand other than the PTO clutch disk, and that proved to be a finger pincher – suggestions would be appreciated on that issue for the next tune up – which will be in about 100 hrs, not 14 years! So in the end, I had fuel tank & carb contamination caused by a broken top on my fuel cap and (the primary culprit) defective/worn ignition components. Thanks boovuc for your helpful suggestions.

[oldredrider 2,547]

Remove the spark plug for easier rotation of the motor.

[GeoPeg 0]

Thanks oldredrider, that was the first thing I did - still was a bit difficult to move it around tho.