04 yfz 450 cutting out at times

I got a 04 yfz 450 that i just bought it runs perfect for a couple mins. then cuts at at mid to top throttle, but idles fine. It has a uni filter no air box lid and baffle pulled out, air/fuel screwed out 2 1/4 times a 162 main but not sure the pilot. Just rode tonight and it run great for about 10 mins then crappy, for a bit. PLEASE HELP!  

do a plug chop when it is running bad and let me know what color you are getting  
Keep it RUBBER SIDE DOWN!!

its a whiteish light brown color. also have adjusted air/fuel screw this evening and put clip in 3rd notch on needle. the problem comes and goes   acts like electrical, but who knows?  

Yea i had the same problem. Changed the plug, my plug was white to a brownish. I checked the gas thought it had enough but with the yfz the reserve sensor is bigger than what you would expect. I thought i had more than enough gas but thats what it ended up being. Mine would run fine until about 4th or 5th gear then it would cut out. If that isnt it let me know!!  

i have an 04 yfz 450 and mine runs good until i am going down the road and am about normal rev and it starts chugging if i give it gas it stops but if i go back down to the normal it dose it again. need help haven't cleaned the carb yet but what should i do.  

I'm not sure what is happening with your YFZ but her some info. My bike would idle good and when the I hit the throttle from idle to full it would either die, back fire or sputter. research told me that I had to modify the ac pump lever. I performed this mod and the bike ran very strong. There are plenty of things you can do to these bikes but I I'm stock with baffle out and ac mod and it runs 90% better. Chugging at mid range sounds like carb. The main jet or clip position. Check out some of the info below.

. Check your spark plug color. Run the bike at idle then shut it off and check it (Pilot jet), hold the throttle to mid throttle for about 10 secs and shut it off instantly and check it (Needle position), then hold it WOT (preferably while riding it) and shut it off and cost to a stop (Main jet). Your plug reading should be a nice tan/brown looking color for the best performance on each check. It is time consuming but the best way to make sure your bike is dialed in CORRECTLY all throughout the powerband. Adjust your jets according to what your plug is telling you

Check the intake going into the carb for stress cracks it is plastic and could be sucking air causing it spit and back fire.

I was reading alot about the bog on the YFZ450, from idle to full throttle the bike will fall on its face.

I removed the cover on the carb (right side) where the throttle cable goes in and tied the ac pump linkage together with wire (called the zip tie mod). This keeps the link together when you stab the throttle.

I first watched the link, it stayed put while the throttle wheel went to full fuel. About 5-10 seconds later the pump link caught up.

After the mod dailed the mix screw to 1 1/4 and I can hit full throttle with excellent response.

I think all of the 450 need this or maybe R&D leak Jet (but i'm new at this). I will try to find more directions on this mod.  See if the spring mod is up your alley. http://yfz450.theatvchannel.com/invision/index.php?showtopic=96984

There is more if you need it all of this is pulled off this forum. The carb is not hard to work on, it just looks hard. Remove air box, gas tank plastic, left side plastic. Then loosen clamps on rubber boots, pull carb out and remove throttle cable, carb should be in your hands then. I know this sound easy but my carb has been out about 40X. I could not get the help I needed and figured it out. This is the reason I am tring to help as many as possible. Get back to us with a better idea of the main problem, most likely ac pump  
Heres my toys
YFZ450 "06" jet kit, zip tie mod, cam mod, sold
Raptor 350 "06" stock, sold
Predator 90 "06" stock, sold

I am told that these bike like to be hard on the throttle.  
Heres my toys
YFZ450 "06" jet kit, zip tie mod, cam mod, sold
Raptor 350 "06" stock, sold
Predator 90 "06" stock, sold

im having the exact same problem dd u find a solution