I have a gravely pm148z. It has the kaw FH641V-AS21 engine on it. Last year it started missing after it had been running for a little while. Come to find out Gravely used the wrong fuel lines in the tanks. They melted and somehow made it past the fuel filter into my carb clogging it. I replaced the tank pick up lines and pickups as well as cleaned the tanks thoroughly. I disassembled the carb and cleaned it thoroughly as well. The mower had never run better. It ran like good for a few weeks, then all of a sudden it started missing again. It would miss under load, but sounded much worse with the deck disengaged. I cleaned the carb good and it seemed to help. I cleaned the carb several times at the end of last season. It seemed to be less effective as I ended the season. I even replaced one of the coils that I thought was missing once once the engine was hot. Now this season I roll it out and clean the carb, change the oil, fuel filter, and checked the air filter. This thing misfires like crazy on high idle. sounds like my hayabusa when I slam into the rev limiter. I did a little research on here and found the pilot air screws covered by a little cap. From the factory the right cylinder was turned all the way in. The left cylinder was turned out 1/2 turn. These seem way off to me. Next I found that one of the main jets is not labeled. the other is marked like 114. The pilot jets are labeled 44 and 46. According to Kaw service manual the pilot jets are correct. However it says that the pilot air screws should be turned out like 1.5 turns and 2.5 turns. Next It says that the mains should be a 122 on the left and a 128 on the right. If I look it up on the online microfiche it shows that they should be both 114. I think the microfiche also shows the pilot jets different. What jets should I be using? Also when I turn the pilot airscrews out to the factory specs the mower will backfire bigtime when I start it. Something interesting is that when I engage the deck to put a load on it the engine seems to quit missing. I have no grass to test it on as of yet. I would pay someone to tell me what is wrong. Im sorry for the book, but I just wanted to give as much info as possible. I have talked to several local shops and the mechanics have no idea. How can i pay somebody 75 per hour if they have no idea where to start? It is so frustrating. Engine has 2000 hrs on it. Please please please help. Im desperate. Hell I will send money via paypal to the person who helps me figure out my gremlin.