i always thought quads ran better in cold weather

 

chaddyb

I am with you that I never want to hurt reliability to get additional power. Since getting my 400ex in April, I have added a pro circuit T-4 pipe, modded the airbox, and rejetted the main jet. The pipe made a great difference in the mid and upper ranges when jetted with a 155 main. The pro circuit is a great pipe and I bought it for $189 from Rocky Mountain. I am slowly working on improving the low end with some mods to the airbox lid. I have put 2 filtered air box vents on the lid so far. With this set up and the stock pilot jet, it runs great in temperatures between 50-90 degrees. I noticed that when the temp was below 50 degrees, I was picking up some hesitation, likely caused by running lean (haven't check the plug). I went back to the solid airbox lid and the hesitation went away. In the spring, I plan on upping the pilot jet to a 42 and lowering the clip on the needle one notch. I then plan on adding airbox vents two at a time until it runs right at that jetting level.

My biggest suggestion would be to make one change at a time. Make the change and get it running right (jetting) and move on from there. The worst thing you can do is to make a bunch of changes, and then struggle to figure out why it isn't running right and what to do to fix it.

 

chaddy

One more thing, about it not running well in cold weather, are you running fresh gas? Gasoline blends are changed during different parts of the year. The EPA makes the gas companies sell "summer" gas that is blended differently than other times in the year. If you are running older gas, try some newer gas and see if this helps.

 

magnum, instead of putting the airbox cover on during the winter to richen your bike why don't you just jump one size in jet and take advantage of the temporary HP increase. It cost $3 and takes all of 10 minutes to do (if that). You are going to get 1-2 HP gain in the cold weather, think of it , you paid $189.00 for your pipe and the most you will get out of it is 1.5 or 2 HP if you're lucky, a new main jet is $3.

 

Rob

I would have to agree with you on changing the jet to richen the mixture. Actually, I have already bought the 42 pilot jet and 160 main, just been lazy lately and haven't put it in. I only noticed the hesitation on the last few rides as it just is starting to get cold up here. The 400ex is getting pushed into the corner for the winter and the snowplow is going on the magnum. Riding time gets pretty limited this time of year as it is hunting season up here. I will pull it out in the spring and rejet that carb at that time. As for spending $189 for only 2hp gain, that tends to be a little deceiving. While the dyno's only show small gains for the addition of a pipe, the throttle response difference was amazing compared to stock. As I did this mod with a 155 main jet at the same time, I saw the effects of both. Besides, it sounds real cool now [img]i/expressions/face-icon-small-happy.gif[/img]

 

I have a 400ex 2002. In dirt wheels they had a pipe shoot out the WB e-series slip on won for best overall pipe it is also pretty quit. Which is goo now a days. Here is what I just did WB e-series slip on, K&N power kit.(includes filter and jets and outerware) You do not have to change the whole pipe in dirt wheels they said the stock head pipe on the 400ex does a great job. With the K&N filter run with the air box lid on and just use the plugs in the lid. Keep this and filter clean. My mechanic I use don't even like the K&N filters because people don't keep up on cleaning them and they will let dirt in, so make sure you keep up on this and on the air box plugs. Here is the cheapest place for the WB slip on www.gopartsdirect.com they were great $215.00 for the e-series slip on with no shipping charge I live in NJ they are in vegas so thats a good deal. The power kit a bought at www.moto-man.com they were $10.00 cheaper then the other web site I gave you. good luck. I love this set up works great. E_mail me if you have any questions. The mention about the filter I questioned at first but these guys fix ATV'S and bikes all day so I take there word.
2002 400ex
WB slip on e-series
K&N power kit
AC nerfs

 

I main jet was re-jetted to 165. In the power kit they have suggestions. If money is a factor you can get the e-series pipe and put it on and go and then re-jet later. Mine runs great at 165 min jet where you live has to do with your jetting according to K&N. sorry forgot to put this in previous response.

 

i planned on getting a wb e series pipe and a k&n power kit but i was curious what it has to be jetted at? i know its different wherever you live but i live in minnesota and i think its below 3000 feet above sea level. no higher. do you have to change the main jet and the pilot jet or just the main jet? what is the stock main jet size, and do i need to go larger or smaller? i would rather not cut holes on my airbox unless i need to, but i will if i have to. also what happens if its not jetted right, does it just run poorly or can you burn the engine down like on a two stroke(at least thats what my sled is like if it runs too lean)? i was just wondering if anyone knew what would be the right jetting for me. i only plan on running it in temps above 50. also if i contact the manufacturers (white bros. k&n)will they help me out, or does it pretty much say when you buy the stuff? thanks for all the help.

 

You could run the e-series pipe without jetting the carb. If you add the K&N filter then yoou have to re-jet. If you are below 3000ft jet is 170 3000 to 6ooo fett jet to 165 this is from K&N remeber all jet companys are have different numbers and sizes. You also have to change the needle. If you want just start with the pipe and add from there. The AC nerf bars look good to. I gave you the web sites to order the e-series pipe for $215. with no shipping. good luck