Service performed today on four generac air cooled generators. Main house unit- air filter, spark plugs and oil and oil filter were changed. Checked valve clearance to find all within spec. Battery checks as good. Reset maintenance schedule and performed function check. System operating normally. Barn unit- air filter, spark plugs and oil and oil filter were changed. Checked valve clearance to find all within spec. Battery checks as good. Reset maintenance schedule and performed function check. System operating normally. Guest house/ lodging- two stand by generators at this location. air filter, spark plugs and oil and oil filter were changed. Checked valve clearance to find all within spec. Battery checks as good. Reset maintenance schedule and performed function check. System operating normally. All systems are performing normally at this time. All systems were cleaned externally and inside of the casings. All batteries check as good. Barn unit showed evidence of a possible