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View Full Version : Is this a good starting point? I'm learning


YFZ450LUV
10-19-2006, 02:49 PM
Does my jetting plan sound correct for starters?

2004 YFZ450-bone stock w/ factory jetting. It is sputtering big time on the top end. I just ordered some parts and here is my plan...

Texas 600 ft above sea level. 50-70 degrees F.
168 main
45 pilot
2 screws out on fuel screw
ncvq needle-what notch?

Thanks!
Samdogmx
10-19-2006, 06:59 PM
yeah that sounds like a good start. I'd say 4th or 3rd notch on the neddle.

remove your airbox lid & take the baffle out of the stock pipe if you havent already & that along with the jetting should really wake it up.
yfz450les
10-19-2006, 08:18 PM
try ur third notch on needle and try 162 main that will probally stop the sputtering on topend.
YFZ450LUV
10-20-2006, 10:23 AM
Thanks guys, I'll give it a shot.
rpyfz450
10-20-2006, 12:19 PM
Sputtering at wide open throttle openings on a completely stock ATV can mean a few different things. When you say "completely stock", does this mean you still ride with the airbox lid on? If so, I doubt jetting is your problem.

I have yet to hear of anyone that had a wide open throttle sputter on an all-stock machine.

The 2004 and 2005 have an electrical defficiency that demonstrates symptoms similar to what you mentioned. If you find the symptoms only appear with the headlights turned off, turn them on to see if they go away. If so, your ATV needs the "resistor kit" (do a search).
YFZ450LUV
10-30-2006, 07:22 AM
Okay, I re-jetted this weekend like stated above and the thing RIPS now! I went 4th postition from the top on the needle. My only question now is, it hesitates down low when you blip the throttle. Besides that it seems to run perfect. No poping or sputtering. Am I slightly rich on the bottom now? What jet controls the bottom hesitation?

Thanks guys.

p.s. I just bought this thing used and it runs so much harder than my Predator 500. I'm excited!!:eek2:
yfz450bk
10-30-2006, 07:53 PM
try playing w/ ur F/A mixture screw...that solved the bottom end problem on mine...and mayb turn up the idle a bit
A A R O N
10-30-2006, 08:18 PM
All the early models have a bog.....Boyesen sells the "quickshot" accelerator pump cover for the carb that will eliminate that, but jetting will not fix the bog when you firs blip the throttle.
YFZ450LUV
10-31-2006, 07:03 AM
Originally posted by A A R O N
All the early models have a bog.....Boyesen sells the "quickshot" accelerator pump cover for the carb that will eliminate that, but jetting will not fix the bog when you firs blip the throttle.

Great, thanks for the reply.
Jube450
10-31-2006, 08:05 AM
Call Laz at GT Thunder, he can tell you how to get the bog out. You need to change the leak jet i believe.
Jube450
10-31-2006, 10:21 AM
Call Laz at GT Thunder, he can tell you how to get the bog out. You need to change the leak jet i believe.
yfz450les
10-31-2006, 08:50 PM
u need to change leak jet to #40 or solder it shut
rpyfz450
11-02-2006, 11:08 AM
Originally posted by A A R O N
All the early models have a bog.

I thought all bikes with the FCR carburetor demonstrated that issue. Not true?
A A R O N
11-02-2006, 11:11 AM
Come to think of it, a friend of mine has an 06 yzf250 and it's got the bog too......maybe all the fcr carbs have it.....I just thought yamaha fixed it for 06, but maybe not.