Bike with cone filters runs lean. Don't want to rejet. Any ideas to richen mixture?

Question

This bike came with cone filters. I have the original air box but it was obliterated. I like the look of the cone filters and it leaves a lot of room behind the heads. Is there a way to richen the fuel mixture by reducing the air flow somehow. Has anyone delt with this problem before? I'm open to suggestions. Fuel economy is my goal. This is a '79 XS750F Yamaha.

My exhaust hasn't been altered. Just the air filter. The carbs now suck too much air. I will rejet if need be. (thanks jetdoc) but I want to know if there is a way to cut down on the air intake at the filters that will bring the mix back into balance.

What is MXPX 465? Never heard of it.

Answer 1

Fit the original airbox or jet the carburators. No other way way. You have tochoose between these two. Thats IF you want to keep your engine working.

Answer 2

You may be looking for fuel economy at the risk of engine longevity. A lean fuel mixture can cause the engine to run hot enough to melt spark plugs, pistons and damage other engine components. This is especially critical in air cooled engines where the fuel is actually used as part of the cooling system.

Even at $3.00 per gallon, burning a little bit of extra gasoline is still cheaper than having to rebuild your engine because you burned a hole in the top of one of your pistons. Especially when you're talking about a 27-year old motorcycle, when parts are nearly impossible to find.

Save yourself money and grief in the long run by rejetting the carbs to a proper fuel mixture.

Answer 3

Try some MXPX 465, anytime I want to richen the mixture I use it. Never fails to amaze me.

Hard to find these days though.

Answer 4

if carb has metering rods with multible postions put clip down a notch to raise needle worth a try if only a little lean but may not some mptorcycles dont have that option larger main a size or two might be another way to help will hardly or not at all notice gas milage.

Answer 5

so what are you doing with your family for Father's Day?

Answer 6

rejet.