m.crusier 120 black plugs

[69mastercraft]

new 120 less than 5 hrs. cyl 1&2 spark plugs black. #3&4 burning perfect. over rich obviously. <br /> But why only two? Each is served form a different<br /> barrel from carb. Now get this. 1&4 from same and 2&4 from same. But one of each is rich? pls help..thanks

 

[RandyJ]

Re: m.crusier 120 black plugs

I can think of only two possibilities... (1) rocker arms are too tight causing two cylinders to more or less flood with fuel...(2) plugs not firing... plug wires or crossed wires. One preliminary check I would do is to start engine and remove one wire at a time to see the difference in drop of rpm. If rpm does not drop on those two cylinders then you can bet they are not firing or not firing properly. Then you can check firing order which I believe is 1-3-4-2 in clockwise rotation. Another possibility is jumping fire from plug wires to motor or metal, another is cracked distributor cap or unclean inside of distributor cap. It wouldn't hurt to give the rotor button a close inspection also.