air/fuel question

[bean2080]

when i bought my quad it already had a hrc kit, cam, jetted and everything but for some reason it had the air box lid still on it. it runs like a top untill you get about 3/4 throttle and it just starts cutting out.

when i take my air box lid off and try to go fast off the start it wont run good, it just bogs. but if i ease into the throttle untill about half throttle i am able to punch the gas and the quad goes really good, no bogging, cutting out or anything.

after all that said, what do you all think the problem is? do you think its a jetting issue or do you think its a air/fuel mixture screw problem? i have messed with carbs before but to be honest they are just not my thing, im just trying to find out what all i will have to do.
thanks

[DnB_racing]

If the engine is running poorly at 3/4 to full throttle, the main jet is the likely problem

[3or4HONDA]

if it is bogging off idle when you stab the throttle try backing the a/f out some.

while the quad is running back the a/f screw out until you get the fastest, smoothest idle then go out another half turn. should not be over 3 1/2 out. if you are bump the pilot up.

and yes if its cutting out past 3/4 throttle increase the main.

[DnB_racing]

when you do try adjusting do only one thing at a time!! fix your main first then fine tune with your lid off or on what ever way you want( I recomend lid off) with good air filter

[bean2080]

yea i may try a bigger jet, would you guys know how much bigger i should go? one size, two sizes, or would you know? it only does it when its above 3/4 throttle, every where else the quad runs great. (thats with the air box on) now when the air box off it bogs real bad intill about 1/2 throttle and after im past 1/2 it will just scream. i am going to take the air box off.

also what is a good air filter? i have always just ran the stock one and clean it after every race.

[DnB_racing]

do you know how to read a spark plug? if not goggle (how to read a spark plug) that's the best way to get the right size jet. your probably going to need around 168 -170 main. for +06 years and a 50 leak(bypass jet) I personally use KN filter but a lot of people swear by foam the biggest thing is to keep clean and oiled. I know it may take more steps to do it this way, but I recommend getting it running right first, with your air cover on and then work at it with cover off, just to make sure that there are no issues at all. but that's just me I dont like to cause more problems until I have one problem fixed.there are some good info on carbs on line check this one but there are many others http://quadhub.com/wiki/index.php?title=Jetting_theory

[Baileygunns]

I don't see a full exhaust in your signature... Take the lid off and bump up your pilot/slow jet. Should fix your issue. If you are running a full exhaust then it might be a main jet issue.

As of right now it sounds like you're running rich on the top and lean on the bottom.

[bean2080]

yea i have a hrc head pipe with a hmf. im going to try the air/fuel screw before i get into it too much and if that dont work ill take the carb apart and see what size jet im running and take it from there, hopefully i can just bump it up a jet size or two and that will take care of the problem.

[RobRacing]

Yeah you need to increase (richen) the main jet. This article (http://www.igoatv.com/2010/06/05/carburetor-jetting-explained.html) will explain jetting more in depth. The reason your quad is running lean is that when you removed the airbox lid and added the pipe it increased the air flow into and out of the engine. When this is done the carb needs to add more fuel to the mixture to even things back out.