1996 ZRT 600. I just got it, first sled. Went 200 plus miles no problem. Now, about every 10 miles it fouls the middle plug. It has BR9ES NGK plugs gappes at 40. What can I look for to solve my problem. It also has 100psi of compression in all cylinders. Is that normal, I figured it should be at 125 plus. It does have 4800 miles on it. Thanks.