yzf 750 tuning problem

Yamaha YZF 750 discussion forum:


yzf 750 tuning problem

yzf 750 tuning problem 
lonnie said 2005-03-12 16:38 
 
hi I´m 18 years old and own a 94 yzf 750r motorcycle that I bought 2 years ago.I have worked in a motorcycle shop the last four years and have been very successful.I have raced dirt bikes the last 2 years and was very consistent. I currently work in an atv and dirt bike shop as head mechanic and I work on bikes out of my own shop. when I bought my yzf 750 it had three rods knocking. Yeah, not good, so I bought a new yamaha crank,crank bearings rods,rod bearings,oil pump,pistons,rings,valves,valve seals,clutch-totally rebuilt the engine. I had the head checked out by Schnitz Racing in Ind,they said the valve seats and guides were ok, so those were not replaced.I did have the head milled .015 because the last guy that had the head off left a hose clamp in the water jacket.So after I replaced all that and put it all back together it ran ok but not right.It would not pull off the bottom right and it had flat spots at 5000rpm and 9000rpm. One of the local shops had ´jetted´the carbs before I bought the bike.When I took the carbs apart they were all messed up. I put them back to stock and it was not much better.So I bought a stage III K&N jet kit and installed it.It runs a whole lot better. It pulls hard off the bottom and strong all the way through.But the carbs hang up at 5000rpm and won´t come back down until you back the idle screw all the way out, then it won´t idle.If you roll the throttle on smooth it runs great,but if you really get in it, it pops at 5000rpm but pulls through it and rips.I would appreciate any help you can give me.Oh yes, I am running the stock header with a vance&hines slip-on. Many thanks,Lonnie. 
 
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