swapping the airbox for inline filter - thoughts By dryshave (Read 1,358 times)

[dryshave]

I've been working with a completely rebuilt Elite250 engine and hope not to use the old airbox. I won't need the vacuum lines for the fuel tank as I will be using the fuel tank with electric fuel pump from a Helix.

My question has to do with the elimination of the airbox and what I am going to have to change to the motor setup with it's removal. IE: routing of vacuum lines for emissions system, routing of vacuum lines to the air intake (carb). Change in jetting?

I've seen lots of photos where the airbox has been replaced with a cone shaped filter - which is what I am hoping to be able to do.

advice on best way to go would be greatly appreciated.

[terrilee]

im pretty stupidBUT
if you do this you are gonna need to re-jet your carb

your gonna get to much air w/o the OEM box

[alleyoop]

No your not stupid Terrilee, your picking up and learning the how-to and what to do things, your doing very well.

Yes Terrilee is correct if you put on a free flow fliter you will need to Up Jet your MAIN JET at least 2 sizes bigger. So you will have to open the carb and hope the MAIN JET is numbered then you can order a couple of jets bigger than what the carb came with. For now LEAVE the PILOT JET alone and get the motor to run in the higher rpms. If it requires a little more fuel for starting or taking off you can richen up the Carb by using the Fuel Ratio Mixture screw. If that is not enough then you change the Pilot Jet but normally that is not necessary.
Alleyoop

[dryshave]

I was pretty sure that would be an issue. By running the free flow filter is there any danger of running too rich or affecting the overall performance.
Will running two sizes bigger cause a reduction in fuel performance?
Looks like I'm going to have to come up with a modified airbox design and I don't imagine that an air scoop would do any good as the airbox is constantly supplying air as the engine is turning over. Will let you know what I come up with - for steampunk scooter project.

[alleyoop]

Dryshave,
Running a FREE FLOW FILTER the danger is RUNNING LEAN not RICH, which is not good your motor can run really hot with a LEAN CONDITION. Running Rich all that does is waste gas and you loose performance. You always have to watch for RUNNING LEAN that can destroy your motor.
Alleyoop

[dryshave]

here's what I'm thinking of doing, but concerned that there's not an "expansion chamber?" which is on the elite and even bigger on the helix... Is that white plastic chamber attached to the carb and expansion chamber... even thought there's not a forced airflow?
I'm able to attach the regular curved tube from and elite 150 with a modified connector to and elite 250 airbox, hoping that'll work for now

[imnts2]

I am always expect any late (after 1968 or so) carburated engine made to be sold in the USA to have a stock set up to run too lean for my tastes. It is set up that way to meet the emissions requirements. The problem is that lean runs hot. High throttle, a little lean and the temperature of the engin rapidly goes up making it run leaner yet. Notice true high performance engines. They blow a lttle black smoke (rich) rich is cooler. Engines love it. I'd rather need to clean the plug now and then. Particularly on an Air cooled engine.

It has to be very very rich to reduce full throttle performance - as long as the plug does not fowl.

Cheers

lefty2

lefty2

[4950cycle]

No expansion chambers on a 4 stroke engine. Only 2 strokes