I have a customers commercial yahzoo walk behind with a 15hp kawasaki FH430V. It is surging badly. The plugs that it came in with were CJ-8's and I know they are wrong.What are the correct plugs. I replaced the carb with a new one and it didn't help at all. Both coils check out fine which leaves me to look for incorrect valve settings. I need the specs for intake and exhaust settings. Any suggestion on what else to look for would be helpful. When it runs we can engage the choke fully and no change in how it runs. The fuel pump is working, the fuel is new, the filter is new I have a set of J19lm's in it. It will start on the first pull but then will only surge, it will not idle ar even run at half throttle. Any help would be appreciated. Thanks.