QuestionQUESTION: Dear Sir;
I recently bought (at an auction) a lawn tractor mower with 140 hours on the clock. The motor data is at the end of this letter.
Problem:
The motor starts easy, idles well, and runs OK at part throttle. However, it sputters badly during higher rpm. It also seems to run hot- the crankcase and overhead valve covers become too hot to touch!
When throttle is opened, motor has major misfires and dies as if it is running out of gas. Misfire decreases/disappears when choke is activated.
Here is a history of what I have observed and done:
1. Cold engine compression test - 160 pounds in both cylinders.
2. Removed engine fan shroud - fins very clean.
3. Installed new Champion RC12YC plugs.
4. Drained fuel tank and filled with fresh fuel and installed a new in-line fuel filter.
5. Gas tank cap vent is open.
6. Checked the in-tank filter - is good.
7. Fuel shutoff valve is good.
8. Checked fuel lines for leaks and obstructions - none.
9. Dismantled carburetor, soaked overnight in carb cleaner, and cleaned it with compressed air. Installed carburetor and used new carb to manifold gaskets.
10. Solenoid on carburetor removed.
11. Installed new fuel pump vacuum pulse hose.
12. Installed new electric fuel pump.
Engine data:
Vanguard Vertical Shaft
Model 351 777
Type 1138-E1
Code 0010 0211
Family YBSXS.5702VK 274834
Air Index of this engine - 3
Complies with 2006 CA Emission Regs
Nikki Two Barrel Carburetor #808240 621266-011
ANSWER: If you choke it when it starts to sputter, will it clean up? Do you have an inline spark tester? This has an electric fuel pump and an impulse pump? What is the make and model of the mower?
---------- FOLLOW-UP ----------
QUESTION: If you choke it when it starts to sputter, will it clean up? [decreases]
Do you have an inline spark tester? [no]
This has an electric fuel pump and an impulse pump? [electric fuel pump replaced the impulse pump.]
What is the make and model of the mower? [Stiga Park Pro 20]
AnswerYou have a fuel delivery problem somewhere. I'd pull the plugs and see what they look like. Gray or white and ashy would indicate a lean condition which is what the rest of your symptoms lead to.
It can be difficult to get these carbs clean and they must be rebuilt with a new kit for good results.
Also, I'd want to check my fuel pressure and volume. The pump should make 5-7psi and flow enough fuel to keep the bowl full, at least an ounce or two a second should be good.
The solenoid on the float bowl often falls apart as does the mating surface on the bottom of the fuel inlet. They seem to have an inordinate amount of problems to me. The fuel lines should also be replaced, this is where a lot of the garbage in carbs comes from, the rubber falling away.
Try these things and let me know what you get. Thanks, PK.
