Carb Needle question

[jwick07]

Okay someone dumb it down for the country boy. Here is my problem, For some reason my 450R keeps falling all over its face when I get to full throttle. I have the HRC hop up kit with a K&N with NO air box lid, and a HMF slip on. The guys that I race with and bought the slip on from said that the 185 main jet would be just fine. But now I keep fouling the plugs. I put a new one in yesterday and couldnt even get close to full throttle before it would start to cut out, just feels the plug just ist sparking at all but when i'm under 3/4 throttle it runs decent not great

So question is, what to do, I think that i need to move the needle clip up one. correct?

so could sombody walk me through how to do this. I have never tore into the carb before and am a little gun shy.

[Pappy]

this may help you

http://www.atvriders.com/articles/jetting.html

[jwick07]

By the way the plug that I pulled out was very black, could this also be due to a bad rev box?? I also run the stock temp of plug should I use a hotter plug??

[Pappy]

id guess you a bit rich. id try a 175 main with needle on the 3rd clip.

[ajr400ex]

Do you have the HRC needle, etc. as well? I think your main should be more like a 190. I run a 185 main with the HRC, HRC air box lid, and stock pipe, HRC end cap. With the pipe and no lid you should be lean unless something else is going on. I have been running the original plug for 2 years now.

I have also had problems with dirt in the carb (more so than other quads). If it was my quad I would do the following: clean gas tank & fuel valve, clean carb., clean air filter.intake, restore needle setting to stock HRC setting if different, try a 190 main jet. The main jet can be changed without removing the carb. Everything else requires plastic, tank, etc. to come off to get the carb off.

Could have an electrical problem too. I would start with the fuel/carb then move to the electrical side.

[Old Head]

I'd say your main is too big since it only controls 3/4 to full throttle.

[tater_kamik]

listen to pappy, definately sounds like you are too rich. if you were too lean, your plug tip would be white if i remember right, and it would run hot

[Pappy]

if it were mine, id make sure the air screw is 2 1/2 turns off the seat and drop to a 170 main. (actually id hand the quad over to matt and he would put it on a dyno for me:D )


if its a stock pilot and its fouling plugs at idle or so rich at idle id turn out on the airscrew 1/2 turn at a time until it got right. but it sounds to me like he is pouring a ton of fuel in it with only a slip on and a 185 main. im running a 165 main, opened lid and full rossier and she runs wicked and thats tuned on the dyno:p

[ajr400ex]

What's odd here is if you have the HRC cam, jetting etc. installed, the factory jetting that comes with it is a 185 main, new needle 3rd clip. 1 3/4 turns out on the air screw. Adding the slip on and removing the lid should put you lean. If you don't have the cam installed, 185 would be way to rich as others have said.

Pappy is right based on what you have shared, it sounds rich.

[jwick07]

Okay this air screw everyone is talking about that is the screw right next to the idle adjustment knob correct.

I going to go to a 175 main jet and the I9 plug instead of the I8 and as ESR rev box