Novice mechanic - need advice

[charlie75]

My son's '05 Yamaha yfz450 broke and I'm broke and no mechanic. Broke 4 months ago - "scrunching noise", locked up and skidded to stop. Would turn over but seemed like no compression. Coolant in oil - cams in proper timing location - over 1/8" valve clearance at TDC at right exhaust valve. Can't afford to box it back up and take it to shop and say, "fix it". Considering selling as is but want to truthfully describe problem with engine in doing so. What is the damage? Drained crankcase and had 1.5 pints coolant and 2.5 pints oil. It sat for 4 months till my son got home from Germany (broke in August, just before he left) Any thoughts?

[F-16Guy]

Take the head and cylinder off and take a look at the piston. My guess is that it probably melted or broke the piston, hence the lack of compression. The cylinder is coated with a very hard coating, so if there are no scratches/gouges, you may be able to have a shop diamond hone it and then you can throw a new piston and rings in it. You really need to tear at least the top end off and find out what condition it's in. Once that's apart, you can feel for play in the connecting rod and crank and see if it's salvagable.

[togup]

with coolant in the oil and locked up youve deffinitly busted the water jacket which means possible whole new top end.

[riggsracin]

they have a crank problem. you just need to get it apart to see the problem. you can check the crank bearings by tring to wiggle the fly wheel up and down and one u have the cylinder and piston out u can check the rod bearing by turning over the crank and seeing if it locks or by moving the rod up and down. it should not move up and down on the crank but alittle side to side

[riggsracin]

drive it down to me. i charge about 1/2 what a dealer ship charges.