Hole in the airbox!!

[ysoner]

Hi all,

My Aprilia Pegaso has a very bad gas mileage (about 25-30 mpg) and I was thinking of a carb cleaning. But I discovered that there is a small hole in the airbox where the air filter is located at, do you think that might be the cause for low mileage?

Thanks
Soner

[WintrSol]

Is the hole in the bottom?
I wouldn't think a small hole would cause a mileage problem. Timing or carburetion is more likely.

[ysoner]

Originally Posted by WintrSol

Is the hole in the bottom?
I wouldn't think a small hole would cause a mileage problem. Timing or carburetion is more likely.

Actually it is in the bottom. I don't know how, but somehow the exhaust pipe touched the box and melted a part of it. Also another thing is that the air filter is unusually clean. I am going to take a picture and attach it.

Thanks
Soner

[rexmitchell]

strange that your pipe would melt a whole like that but I guess its not too far out.

[ysoner]

So here is the picture of the airbox. You can see the hole in the right. My guess is the air goes out from that hole without even entering the filter thus the engine burns a way rich blend of fuel. What do you think? I also attached a picture of the filter, which seems so clean to me.

[EatSomeIron]

i would have thought it lets unfiltered air in, letting you run lean... but who knows i guess.

[Dodsfall]

I would guess too lean as well if the fuel mixture is getting changed.

Check your spark plugs and see what they look like. That will tell you right away if the fuel mixture isn't right.

Edit: You can epoxy a small piece of plastic over the hole if it's causing issues. Just make sure the exhaust gets moved away from the airbox.

[WintrSol]

Originally Posted by ysoner

My guess is the air goes out from that hole without even entering the filter thus the engine burns a way rich blend of fuel. What do you think?

Fair guess, but really wrong. The engine sucks in air through the air filter from the box, so the air box can't let air out. It can, however, let more air in.

Looks like that round port in the center has a seal for the filter, and is the engine intake. That would mean the air is still filtered, but you may be getting just a little more in, since the air entering the box has more holes to pass through; maybe not.

Your mpg problem is elsewhere.

[ysoner]

Originally Posted by WintrSol

Fair guess, but really wrong. The engine sucks in air through the air filter from the box, so the air box can't let air out. It can, however, let more air in.

Yep I figured that too. In fact I took the bike to a service today and they told me that the main problem should be clogged air filter. But i am going to have a carb and timing check anyway.

And a related question: a mechanic told me that instead of cleaning the carb, I could add some fuel additive into the gas tank so that it will wash away the dirt in the tank. Does this make sense to you?

Thanks for all the valuable feedback

[Dodsfall]

A fuel additive such as Seafoam won't really wash away dirt, but may help remove deposits in the carbs from old fuel. It's cheap and worth a try.

[WintrSol]

Dodsfall is correct, if you have actual dirt, like bits of rust or sand, you have to remove it mechanically (wipe it out). Seafoam, and its ilk, are meant for deposits left by gas going stale and evaporating, which will dissolve in a solvent.