Understanding the Problem:
* Gas in the oil: This usually indicates a faulty fuel system component allowing gasoline to leak into the engine's crankcase.
* Blown engine: While gas in the oil can sometimes lead to engine damage, it's not always the case. However, driving with gas in the oil for extended periods can cause significant problems.
Possible Causes of Gas in the Oil:
* Carburetor Problems:
* Float needle valve stuck open: The most common cause. This allows fuel to continuously flow into the engine.
* Carburetor float level too high: Causes fuel to overflow into the crankcase.
* Dirty carburetor: Buildup can obstruct fuel flow and lead to erratic behavior.
* Fuel Pump Malfunction: A faulty pump can deliver excessive fuel pressure, forcing it past seals and into the crankcase.
* Damaged Intake Valve Seals: Worn or damaged seals can allow fuel to leak past into the engine.
* Cracked or Damaged Engine Components: In extreme cases, a crack in the engine block or cylinder head can allow fuel to enter the crankcase.
Troubleshooting Steps:
1. Inspect the Carburetor:
* Float Needle Valve: Carefully inspect the float needle valve for wear, damage, or debris. Make sure it moves freely and seals properly.
* Float Level: Check the float level according to the manufacturer's specifications.
* Clean the Carburetor: Thoroughly clean the carburetor with a carburetor cleaner. Ensure all jets and passages are free of obstruction.
2. Inspect the Fuel Pump:
* Check Fuel Pressure: Use a fuel pressure gauge to measure the pump output. Compare to the manufacturer's specification.
* Fuel Pump Leak: Look for any leaks at the fuel pump itself or its connections.
3. Inspect Intake Valve Seals:
* Visual Inspection: If possible, inspect the intake valve seals for wear, damage, or cracks.
* Compression Test: A low compression reading can indicate damaged valve seals.
4. Engine Inspection:
* Visual Inspection: Look for any obvious cracks or leaks in the engine block, cylinder head, or oil pan.
* Pressure Test: A pressure test of the engine block and cylinder head can help identify any leaks.
Important Considerations:
* Timely Repair: Addressing gas in the oil promptly is essential to prevent further damage.
* Professional Assistance: If you are not comfortable with engine repairs, it's highly recommended to seek professional help from a qualified mechanic.
* Engine Damage: If the engine has already sustained significant damage due to gas in the oil, a full engine rebuild or replacement may be necessary.
Before you start any repairs:
* Safety First: Always work on a clean, well-ventilated area. Wear safety glasses and gloves.
* Refer to the Service Manual: Consult your Yamaha Grizzly 660 service manual for detailed instructions and specifications.
Let me know:
* Have you already tried any troubleshooting steps?
* What symptoms are you experiencing besides gas in the oil?
Once I have a better understanding of your situation, I can provide more specific advice.
