Home › Forum › Ask A Member › compression for QD-17 › Re: compression for QD-17
Overheating affects the pistons and cylinder walls mostly, bearings/bushings are usually not affected much. The high heat can cause cylinders to distort/become out of round. The high heat usually causes the pistons to smear/scuff some material onto the cylinder walls which may also partially trap the rings in their grooves. The high heat often causes the cylinder head to distort and burns the head/exhaust gaskets. You have the head off, so be sure to check it carefully for flatness (along with the cylinder deck) before replacing the head gasket. Pulling the exhaust cover is a "judgement call", mostly determined by whether or not the engine has been used in salt water, sounds like your engine is a fresh water engine. I guess I would try to loosen the exhaust cover screws, but surely wouldn’t force them if they seem stuck/corroded in place, those little screws break off easily and are a bear to drill out/helicoil. Removing the exhaust cover will allow you to see a more of the piston ring/cylinder wall situation. You might consider removing the intake bypass covers which will allow a peak at the intake side of the pistons, these screws are easily removed. Again, don’t force those exhaust cover screws, leave it alone if the screws are stuck. Be sure to clean all cylinder head threads and use sealer on the threads/gasket during reassembly.
You don’t report seeing any aluminum transfer onto the cylinder walls, and only the usually minor scratches/scores that are found on most of these engines. So, I really think you will be OK and have a nice running QD once reassembled. Again, don’t be afraid to "rough up" those cylinder walls with some fine emery cloth, simply blow out any dust with compressed air/carb cleaner spray.
Be sure to post pictures if you have more questions or want more opinions on internal condition.
One final note, these engines are known for premature wrist pin/bushing wear, so be sure to rock the crank back and forth slightly looking for "lost motion"/listening for the clunk which may indicate problems.