I recently bought a 2005 YFZ 450 and find it to be a little lagging on the big end. Its been pretty cold around here so I have been running with half choke alot of the time so I thought maybe thats why its doggy. temps reached 40 and it still was a pooch with no choke. Is this pretty normal for these quads or am I having motor problems. I only have maybe 3-4 hrs on the motor but it just falls on its face in fifth gear. Does a pipe cure this or any other options?

 

I was riding a 450 yesterday in 30 degree weather. Half Choke??? i think you gots a little bit of problems

 

but at the same time, i have noticed that 450s are a little more boggy on the top end. I ride a banshee, and when i race my buddies 450, he whoops me off the line, but when i klnock it into fifth, I gain on him.

 

There are two settings on the choke pull one click out half choke two clicks out full choke.If I dont run it half choke it will hardly run or idle when its cold.

 

mine ran fine in -5 with no choke just about 15 min warmup time. so i have no idea what you are talking about [img]i/expressions/face-icon-small-confused.gif[/img]

 

yfz's are lean from the factory. jetting with stock setup should be 45 pilot, 165 main, drop clip postion one clip. cold weather you may have to increase your main jet to 168. increase in elevation you will have to decrease your jet. you may have to adjust your fuel mixture screw as well. recommend buying a Zip-tye® for doing this. when jetting...always go big then work your way down. when the power comes back your there. hope this helps, good luck.

 

I am at about 500 ft above sea level so maybe thats why I am running leaner. When I bought it they said they jetted it for cold weather. Now I am thinking that maybe they went the wrong way on the clip. But that still shouldnt make a difference on the big end. Your main jet should be the only thing changing that. Thanks Deimos
for the info. Does yours run hard in 5th gear?

 

Mine pulls like a raped ape through all gears in all ranges. It does flatten out in 5th at full throttle but every 450 will. What you wanna achieve is a quick revving bike. There is only so much you can do with top speed, but I think what is more important is how quick you get there. When I first started jetting my bike, I made the mistake of going from lean to rich. Its really hard to notice differences doing it that way. Lean will always be quick and fast, but too lean can hurt the motor. Once I got rich then came back it was like night and day. So I could of saved myself alot of time by just going really big from the get go. So go big and start dropping down in small increments. You will feel and hear it when you got it right. Sometimes after you go up in two main jet sizes, you will have to drop needle clip position. Once you do that, you may have to back off a main jet... i.e. 3rd clip position, 172 main to 4th clip position, 170 main. Reason is...the areas that the needle and main jet affect over lap some what. Needle is 1/4 throttle to 3/4 throttle and Main is 3/4 throttle to wide open...generally speaking.

 

Iam familiar with scary jetting. I have been racing snowmobiles for 15 years. nitrous, nitro ect.. Jetting gets hard. But this seems almost like the motor is already tired.

 

Or maybe I am already to used to it and its seeaming slower.