D2 Pony kicking my ass!

After a good cleaning of the fuel system, the pony on my D2 5U1731 has been starting reliably first or second pull for several months.

On Saturday it held true and fired right up. I spun the diesel for a bit and it roared right to life. I shut the fuel off to the pony and she sputtered and died before long. I switched the magneto off. After a good warmup, I skidded logs for maybe an hour and a half, and then thinking how great my little Cat runs, I shut it down for lunch.

After lunch the pony popped on the first pull, popped on the second pull, and that was it. Plugs were dry, but had spark.

I topped off the fuel, cracked the fuel line open at the carb inlet, and confirmed fuel was at least making it that far. Pulled and pulled, nothing. Had to get the job done, so I jumped on the modern green tractor and finished cleaning things up.

This evening, thinking maybe the little Cat had just gotten tired of skidding logs yesterday, I gave her a few pulls, nothing. OK, off came the hood and fuel tank, as well as the top of the carb. There was fuel in the float bowl, and no gunk or debris. I pulled the main jet and cleaned it just for good measure. I put it back together and listened to fuel flow to the carb again. Gave her a few pulls, nothing.

Checked spark again, good.

Full throttle, full choke, pulled and pulled and pulled and friggin pulled. Nothing. Plugs are dry. It has compression.

There has to be debris in an orfice somewhere. Anybody got any hot tips on where to look?

Funnily enough, one of our Directors, Aaron of LAOL YouTube fame just produced a video dealing with some pony issues. Might help?

https://youtu.be/oG5LbFhm0wQ?si=kIQtZSHbalcvp5Jg

Potato, if your fuel bowl is full, and your main jet is clear, then you may have a blockage in the passage across the bottom of the bowl, or in the thin brass rod that passes across the throat, just to name a couple. Do try the easy option first though which is to remove the crankcase oil fill cap and the fuel tank cap, then try to start it. If that doesn't work, then best to remove the carb, start at the beginning, and follow the fuel flow through the various jets and passages and establish positively that they're clear. Don't forget the idle jet system which terminates in the idle jet plug adjacent to the closed throttle plate. You can clean that by making a note of its orientation and depth set, opening the throttle and punching the plug through into the throat. When you've cleared the passage, refit the plug by carefully punching it back in from the outside

Mr Neil. May I ask what it does to remove oil and gas caps. Never heard of it. Thank you

Pota'ter : Sometimes a pony needs help getting fuel. I have blown into the tank or primed a spark plug with gasoline to give it a boost. Easier than tearing into the carb. JM

What JM said for the fuel tank, and for the oil fill, if the crankcase is overfull, it can actually prevent the carb from flowing fuel because the crankcase pressurizes, and in turn increases the pressure on the engine side of the carb venturi, negating its effect. It was night and day for starting one of our ponies. We had checked the oil level before starting but it filled (with gas) while we were messing with it.

Thanks everyone for the great tips. I’m hopeful that it just needs a little persuasion to get the gas flowing again. It started and ran so well up till now that I can’t help but think it must be something simple. I’ll try the tricks mentioned.

Crankcase pressurizing the venturi on the carb - ???

What Prevents the engine from thowing volumes of oil out of the open crankcase?

Sorry - I don't follow that theory - Carburetor is on the Intake side, controlled by the intake valve. When the piston is on the intake stroke, it pulls the air/fuel mixture to the cylinder through the carburetor. When the next cycle begins at Bottom Dead Center it becomes the Compression Stroke and both valves are closed. Reaching Top Dead center, the power stoke begins, driving the piston back to Bottom Dead Center where the return to Top Dead Center is the exhaust stroke, exhaust valve is open. Thus the 4 cycles of a 4 stroke engine. Number of cylinders does not change this operation nor does the orientation of the cylinders.

Venturi depends on the increased velocity of the air through a necked down throat. This is where fuel is atomized and the mixture continues to the cylinder on the intake stroke. IF one of the "jets" is not functioning, or the needle valve adjustments are too tight, float level too low, etc, the fuel will not be drawn to the intake stroke. TOO LEAN TO BURN.

I just finished wrestling with a 3hp Briggs & Stratton with Airgov Carburetor. It would not run or start without priming with raw gas, then only run with the choke nearly fully closed. Without an Air Compressor, I have no way to force air through the orfices. Second tear down, nothing apparent, but I used a bristle from wire brush, put back together and it runs like a top, starts on first or second pull. Just one example of why it is so important to keep fuel clean and be meticulous when working items.

My Dad was a great mechanic - WW2 veteran as a Heavy Equipment Mechanic with the US Army, Okinawa 1945-46. He had a standing rule that works most of the time- "when you are positive the problem is Fuel - look at the ignition system, or vice versa"

A trick he used when installing or cleaning ignition points - wash them with starting fluid - let it evaporate then put the rotor and cap back on. Don't forget to let it evaporate! The starting fluid washes any chance of oil from the point surfaces. (failure to let the vapors dissipate will result in quite an explosion, distributor cap becomes a projectile.)

One item ofen overlooked and one that causes multiple problems - the ground wire on the magneto to the switch. IF there is any fault in that circut, it will prevent the necessary hot spark from reaching the spark plugs. Most of the Cats on the farms here had that wire "pulled" off - just one more reason to let the pony run out of fuel, preventing additonal problems!

CTS

That’s exactly how I clean and wake up the points on my mags, except I use brake cleaner seems to clean them up and works quite well!

Crow Fighter that was a good lesson for me. Small engines have never cooperated with me when not almost brand new. I use the nonethonal fuel and I think it helps. Come to think about it, bigger engines are no easier for me either. I’m just glad my pony motor has electric start. Thanks crow fighter

No need to apologize. If you'd like to see it, overfill the crankcase then try to start the pony. You'll know when you have enough overfill as the pony will not start/run, even if it did before. If you then remove the oil fill cap, it will likely then start and run, albeit poorly