I can't get this beast to start has spark . new plugs. new ign wires. rebuilt carbs. cleaned tank.new gas lines plenty of fuel .commpression good .tested impulse line with gauge will fire but will not start???? any idea's would be greatly appreciated

I have a 1993 Safari 377 that occasionaly won't start when it is warm. Most of the time it starts after waiting a few minutes, but today it would not. I checked and there was no spark. After about 1 & 1/2 hours it still wouldn't start with the electric starter, but ten minutes later it...