a buddies problem, running mostly stock motor, with Toomey t5's, stock carbs with 350 main jets, stock needles, weisco pistons, cool head. hes run it all over glamis, not counting numerous trips, then under a good warm daytime load, it scorched the right piston. he got the motor top end redone, new weisco's, and out in similar conditions, with a slow relatives daughter riding it, same clutch side piston comes out with a hole and top ring landing melted down, supposedly she never rode hard, he never had a chance to check the plugs for any lean condition, im having trouble beliving a hole could melt at lower power level activity, theres no visible vacuum leaking around carbs, if the crank seal was pulling air it would include oil from the trans right? anyway im helping to hopefully prevent reoccurrence, talked to Toomey about correct jetting, his needle kit has slimmer needle and 280 main, for sea level operation. so im wondering if im overlooking something else, to check seal integrity, would pouring solvent in case to monitor for any loss indicate seals ability, well enough to rule out failure?