18 Mag Starting Issues
 

Hello all! I have a 784 with an 18 Mag & Walbro Carb. Having problems with the engine starting consistently. If I get it to run once, it will start every time. Once it sits for a day, it will try to fire and sputter on the first crank and will never take after that. Went through and cleaned the carb. When my buddy and I took the carb apart, we found a lot of dirt, so we installed an Advance Auto fuel filter in the line. Haven't had the carb back apart to see how well it worked, but I'm thinking there's still dirt in the carb somewhere.

Anybody have any suggestions?

Where is the Fuel Filter installed...??? And what type of Fuel Filter did you install...???

Fuel filter is intstalled on the engine side of the firewall. It is a $3 part from advance that is a small fuel filter for small engines. However, it is important to know that the starting issues were not affected by the installation of the filter; it was doing the same thing before.

My 1812 did about the same thing. (same tractor as your 784). I would start than would not start again. I had to pull the motor and put a new coil on in it. it is on the back side of the motor. The coils are around 120$ but it worth it! Pulling motor is not hard six bolts and wires and the gille and then it is out. Put new motor mounts it and aircraft bolts and blue locktite. Than clean the motor super clean. Gap the coil at 10 thoundths. Put the motor back in and it will fire right up! My 1812 runns 10 times better now and you bump the key it starts right up.

Does it fire if you give it a shot of gas down the carb? You could have a fuel pump problem also. If it fires by putting gas down it then bypass the fuel pump and have at least a 1/2 tank of gas an try to start it. I would try this first and then move on to the other possible problems. Good luck and keep us posted.

My 1872 is the same way today, but , I know what the problem is because I created the problem.

The 90 degree snorkel kept vibrating loose, so I used Locktite on the screws.

Some Locktite got on the choke shaft somehow, now it is difficult to pull the choke all the way out.

Partial choking causes the exact symptoms you described.

I keep waiting for the Locktite to wear away, but, 6 years and the choke on the SuperCub still requires a SuperYank!!

As for the coil, it's not an ignition problem, it's a fueling problem as far as I can tell. A shot of gas in the carb will start it right up. Also, I will add that when we put the fuel filter on, we cranked the engine to run fuel through the lines. The fuel pump was putting out a lot of fuel.

How old are the fuel lines? Are they original?

They seem to be in pretty decent shape. I'm thinking tomorrow will yield another look at the carb and see if there's still sediment in the bottom of the bowl - this would prove whether or not the grit is coming from the lines or from the tank.

Dog

If you have dirt back in the carb, then take the time and wash out the tank, and replace the fuel lines from the tank to the carb. Youll thank your self in the long run. also like Lew said the fuel lines can look good on the out side but rotting on the inside.

On another note, its about time for you all in Western pa to hit the woods. Wish I was making it up there to hunt this year.