A recent top-end rebuild on a Yamaha Banshee revealed a Head Gasket Leak. After installing a new OEM top-end kit, including Wiseco pistons and gaskets, a small imperfection was noticed on the head gasket near the right cylinder’s water jacket. However, the left cylinder exhibited more significant leakage.
To address the issue, Permatex copper gasket spray was applied to the head gasket before reinstallation, following the manufacturer’s guidelines. A second heat cycle showed no apparent head leakage, and the engine performed flawlessly. However, a few drops were observed near the exhaust towards the end of the cycle, potentially originating from the overflow, a full tank, or the front cylinder base bolts.
Further inspection after cooling revealed a possible leak from the lower cylinder bolts. The next step involves removing the cylinders, applying copper spray to the base gaskets, and conducting a third test. Given the new components used in the rebuild, issues with cleanliness or trueness are unlikely. The head itself appeared in excellent condition upon removal, with no signs of coolant entering the cylinders. The leak was clearly external, around the bolts and flange.
The current hypothesis is that applying Permatex to the cylinder base gaskets will resolve the remaining leak. This detailed troubleshooting process highlights the importance of careful inspection and persistent problem-solving when addressing engine leaks. The use of copper gasket spray as a sealant is a common practice in addressing minor gasket imperfections. Further updates will follow after the third test is complete.
