Short Story: Pulled the head apart trying to figure out why the kart wouldn’t start and found water was being pushed into the cylinder and into the exhaust, and exhaust was entering the coolant fill. Pics of the wear below. Plan is to replace the jug head due to what looks like corrosion, wiseco std piston kit with new gaskets, and clean up and scotch brite the cyl wall. This is my first rebuild and have no expertise on the signs of wear. Any suggestions and tips for cost savings but solid direction is appreciated.
Pic of the jug top. Looks like corrosion or pitting?
Pic of the piston. Excess wear on the exhaust side, not sure if this is because the engine is mounted in an angle towards that side? Also has similar corrosion marks on the extreme edges, mostly on the intake side.
Pic of the cyl wall. Matching wear on the exhaust side. Will a hot tank cleaning and scotchbrite red be sufficient?
Long Story: Purchased the kart used and noticed it needed an extra turn or two to crank but always thought it was rich. Engine has about 4 hours since I purchased (unknown hours since last ring replacement but motor was super clean). Last session two weeks ago, kart ran fine but noticed the coolant fill bottle fell off during my last run and the hose was dragging a bit on the rear axle. After sitting for two weeks, I purchased a new frame to swap everything over. Once complete, the engine wouldn’t crank at all. Pulled the spark plug and saw that it was wet from water. Pulled the exhaust off and the entire thing was full of water. Opened the coolant fill and saw exhaust smoke and no water. Not sure how it could have gone from running decently to dumping water in the exhaust but that’s where I’m at now. My only guess is on my last session as the coolant bottle dragged, it let out some water possibly causing the engine to get warm and damage one of the 2 main jug gaskets.
Freddy is one the money with the upper end rebuild advice. While you are at it, check the shaft seals on the crank and for cracks in the carburetor boot. While the crown of the piston looks like the engine has been running rich, the damage to the skirt and pitting on the piston surface look like damage from being run too lean. Leaking crank seals and/or a cracked carb boot can cause this and make proper jetting impossible. Burned one down for exactly these reasons with similar looking damage.