new power head fouling plugs

2004 hpdi vz came apart @298 hrs, new power head,1 injector,2new reed blocks and reeds,2thermostats,balancer and plugs.changed plugs after break in.probally 15 hrs on motor since with alot of time between 3000 and 4000rpm.motor started missing so I stopped and checked plugs,bottom starboard black and fouled out.middle plug same side kind of dark ,all other plugs looked very good.does it sound like a probnlem to worry about or do theese motors just foul plugs?my first yamaha and not having to good a luck.any opinions and thanks


Modified by sportmanb at 8:12 PM 5/6/2008

I just had the same repairs to my 2004 225hp HPDI. Four short trips out on the lake and on the fifth my engine started missing. It is back in the shop now. It was there five weeks to replace the powerhead and I am getting sick of this!

After a new powerhead is installed,does one have to go through the break-in period again?

yes.