Air box mods

gday guys..... whats your thoughts on air box mods on a YZ250F with a big bore kit (290)????

i always thought more open the better, is this true??



No. Ideally, there will always be a slight restriction in the inlet system to provide a more significant vacuum signal. Another thing to consider is 'need' You have a 55 gallon drum and want to pour a glass of water in it. How large and opening do you need?

A 250F needs about a 2 X3 inch opening to flow plenty of air. Larger, you'll weaken the vacuum signal and have to compensate with over size jets. Larger jets does not always mean you are giving more fuel. It can (and does in this instance) that the suction from the engine is weaker and it needs a easier flow to get the correct fuel volume.

Thanks will for the advice.. I think I'll leave the air box alone


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now