Air Intake

[ALIZARDONROIDS]

81 Suzuki GS450T

Trying to decide if I should switch out the old air box for pod filters. I am not able to get a good seal on the intake side of the carbs because the plastic on the air box is so old. I would like to hear what you guys think about this mod. Will I need to rejet the carbs or will I just need to do some adjusting to get it to work with some pods.

[WintrSol]

You may need to put slightly larger main jets, because the reduced restriction in the intakes will tend to lean it out. If you have adjustable needles, you might just move the clips a notch or two towards the long end, and be OK, especially if you don't use more than about 1/2 throttle much. A tweak on the idle mixture screws will likely be needed, too, but if you get more than about 3 turns out, larger pilot jets may be needed, too. It all depends a lot on how much less restriction the pods have, compared to the stock filters.

[ALIZARDONROIDS]

Hey thanks,

My needles are not adjustable, but I will hook the pods and see how it effects the mixture.

[WintrSol]

Best done with fresh plugs and a throttle chop after running for about 10 minutes at a steady throttle setting, preferably above about 1/4 throttle. Then, look at the plugs for color; that will tell what the mixture is like at that throttle setting. It's hard to assess the 3/4 to full throttle mixture this way, unless you use a dyno to do the test, but you can get the low- to mid-range, needle controlled region this way.

BTW, a throttle chop is done by pulling the clutch in and flipping the run/stop switch to stop at the same time, then pulling to the side of the road. Take your plug wrench and work gloves with you.

[ALIZARDONROIDS]

So there is a breather hose coming off the valve cover that is connected to the air box. I am just wondering if it is just used to remove heat or is it actually a vital vacuum hose. The service manual just calls it a breather hose so I think it should just be for removing hot air. The reason I am asking this is because when I remove the air box and install the pod filters there will be nothing for that hose to reattach to.

[Dodsfall]

Originally Posted by ALIZARDONROIDS

So there is a breather hose coming off the valve cover that is connected to the air box. I am just wondering if it is just used to remove heat or is it actually a vital vacuum hose. The service manual just calls it a breather hose so I think it should just be for removing hot air. The reason I am asking this is because when I remove the air box and install the pod filters there will be nothing for that hose to reattach to.

That is the crankcase vent. Since the pistons are moving up and down, they push air in and out on the "back" side of the pistons in the crankcase just like on the "front" side where combustion takes place.

If the crankcase were sealed up tight without a vent, the pressure would simply blow a gasket somewhere and make a mess.

On more modern engines, the vent is routed back into the air box to catch any blow-by flammable gasses that get around the piston rings to be re-burned in the combustion chamber. You get slightly better fuel economy by recycling the gasses and the engine doesn't pollute as much.

The important thing to do when removing an air box is to make sure that the vent hose is routed someplace where dirt and moisture is unlikely to be sucked into the crank case through the vent.

[WintrSol]

Originally Posted by Dodsfall

The important thing to do when removing an air box is to make sure that the vent hose is routed someplace where dirt and moisture is unlikely to be sucked into the crank case through the vent.

You may even want to consider a filter made to go on the breather hose; they are usually metal element filters, just to keep dirt and water out.

[ALIZARDONROIDS]

Thanks guys. I will look into finding a small filter for that hose.