Having now got my YZ450 legal to road ride, I am experiencing a light throttle stutter. I have searched TT to find a lot of information on where to start looking, so tonight, I went for a ride and tried richening the pilot screw. This did help marginally but it also highlighted that on very light throttle, the stutter went, on light throttle (like cruise) the stutter is random, occasionally very rare to happen lower down (say 2500-3500) but mostly often stuttering getting worse at 4500-6000 rpm.
So I came home and checked the TPS. This is slightly out of spec. The closed throttle reading is 0.6 and WOT is 3.9. I removed the carb and adjusted the TPS to gain a higher reading, I only mustered 4.1 on maximum adjustment. I removed the TPS and noticed that the plastic locators on the switch were worn. I check the switches range off the carb and read 0.2 closed and 4.6 open. I'm going to order a new TPS as I think this one of worn.
Next I started removing the jets, everything is standard according the manual but the needle looks worn with obvious signs of scratching to it. I'll replace this too but having the stutter and having read what I have read regarding others experiences with this kind of hesitation, should I change the NFLR for a NFPR?
I'm not sure what to do with the rest of the jets, just leave them standard?
The bike is pretty much standard apart from a twin air filter and a de-baffled '08 silencer (straight through). The bike also has the optional Yamaha power bomb front pipe. It seems to run ok other than the stutter, seems powerful and has little popping on deceleration although it did give a back pop on a gear change tonight but that is the only time it's done this.
Any help would be very much appreciated as it is a PITA to remove the carb on this bike lol.