How to Troubleshoot a TRX 250X Blown Head Gasket

The TRX250X is a popular entry-level All Terrain Vehicle from Honda Motors. The TRX250X is equipped with a 229cc, air-cooled, OHV, longitudinally mounted, single-cylinder, four-stroke engine. The head gasket is a common area of failure in single-cylinder engines such as the TRX250X's; the result is reduced engine performance, engine fouling and ultimately complete engine failure.

Instructions

    • 1

      Examine the exhaust vapors coming out of the exhaust pipe when the engine is running. If the head gasket is in good condition the exhaust should have a small amount of water vapor when the engine is cold, and should be practically invisible when the engine is warmed up. If you see blue-gray smoke in the exhaust and detect an oily odor, engine oil is leaking into the cylinder. This is most often caused by a leaking head gasket, but can also be caused by worn cylinder valve guides or a defective valve.

    • 2

      Locate the joint between the engine head and the cylinder block. Look at the top part of the engine (the part with the heat fins). Note that this part of the engine has a division about half way down, where you will see a thin crack between the upper part (the head) and the lower part (the cylinder block). With the engine running, check carefully all the way around this crack, looking for signs of oil leaking out or exhaust gases leaking out. If either of these are leaking it indicates a leak in the head gasket. If your engine is dirty and you cannot see the joint clearly, clean the joint off using Q-Tips and brake cleaning fluid.

    • 3

      Consider the performance of your ATV. A blown head gasket will cause a deterioration in engine performance. Common symptoms are lack of power, engine hesitation under throttle and difficulty in engine starting. If any or all of these symptoms have suddenly appeared, a blown head gasket could well be the cause. If these symptoms have been gradually building over time, they could be due to wear of the cylinder, piston or valves.