Ive searched but could not find a definitive answer. I just got a fatboy 4 pipe from duncan. I installed it and did their recommended jetting. It will fire up and idle fine but when i go to about 1/3rd throttle it studders real bad and im afraid to rev it up more. When i let off the throttle the first bit of throttle is fine. And when in neutral it seems to run up fine with a hint of balck smoke coming out (i think thats just the new pipe and some oil left in it from manufacturing). im new to jetting so im looking for reccomendations please. Heres what i have:

05 yfz450
pro motion twist throttle
K&N pro design filter
no airbox lid
Needle stock 5th clip down
180 main jet
45 pilot jet everything else is stock.

Two notes when you install the twist throttle i believe you cut the two wires for the tps and tie them together. Second when i was working on the carb i think i slid the tps down because it looks like you have some adjustment.

Im in central florida real close to sea level (under 500 feet max) The temps have been between 70 - 90 degrees. Any help would be greatly appreciated. Thanks in advance

 

shoot i dont know, ide say try a leaner jet, but your low allrdy, man this is going to keep me up all night thinking about this..

 

Hey guys, sounds a little rich (black smoke). Try leaning it out a little on the needle and check your plug after a run. There is lots of info for jetting in the forums. it helped me alot, just use the search feature. Hope everything works out for ya.

 

Get the NCVQ needle anf try it on the 4th.

 

I'm not to familiar with the YFZ but it sounds like you are a little rich in the mid range.Black smoke indicates that.Your carb settings are closed to 1/4 throttle is pilot,1/4 to half is needle,half to full is main jet.Being at sea level your air is more dense "heavier"higher altitude is thinner.Sounds like you are rich in mid range try moving your needle.Do a plug chop and see what it is doing,cardboard color is about right.Do only one adjustment at a time.You will get it with patience.Someone jump in if I'm wrong.This has been my experiance.GOOD LUCK!

 

Thanks guys i tried all of your reccomendations. Unfortunately after diagnosing it is an electrical problem. The rev limiter is kicking in about half throttle. Im bringing it in to yamaha tommorow to find out exactly whats wrong the guy from the dealership who looked at it today quickly said it is just a coincidence it happened when i put the pipe in. He's not 100% sure but hes gonna try his electronics on it to find out exactly whats wrong. Now it wont start in gear or without the clutch pulled in ine neutral. Sometimes when it stalls i have to shut the key off and turn it back on to start.

 

my dealer in town told me with all that stuff use a 175jet 45pilot and the gytr needle... 180 seems kinda high for that bike...

 

Stock needle may be ok, or may be a little lean. Might try going to the 6th clip position, or going to the NCVQ needle on the 4th clip as already mentioned.

180 on the main sounds HUGE! [img]i/expressions/face-icon-small-shocked.gif[/img]
I would think that a 175 would be more than enough.