Oil Pressure ?

[stunva]

I changed the oil on the Hayabusa today and noticed two things, the oil wouldn't drain out quickly unless the oil filler cap was out, I thought funny but fair enough. Then after I was finished the change and ran it for a while and went to top it up as the oil filler cap became loose it sucked air in like there was a reasonable vaccum there, is this normal for the Hayabusa, I've never noticed it on any of my other bikes.

Stu

[stunva]

I've been looking at a few diagrams, would it be possible that someone has connected the crank case breather hose and the pair hose from the air box together as some kind of mod ?

[stunva]

From Hayabusa.org

The crank vent/pair mod is combining two systems to put suction on the case. If you just remove the PAIR, you will not touch the breather tube.

The Crank tube comes off the top of the crank case above the tranny and behind the cylinder bank.

You get to it by lifting the tank. That tube goes to the airbox I think.

The PAIR also goes there for clean air to inject into the exhaust.

Someone came up with the idea to connect the breather tube straight to the PAIR suction tube to draw vaccuum on the case.

This is supposed to create a better ring seal and more HP.

[Greeny_SA]

Heard of that mod but as with a lot of these so called improvements they are Not what they are cracked up to be . That one was not taken up generally on this forum ,But the mod of blanking off the pair to stop backfire is more common. This was just stuffing a marble or bolt up the rubber pair valve tube to blank it off . I have a 2000 & have done this & it works . I'm no expert & if I'm telling you Bullshit someone will correct me.

[Maj]

Yes the pair to crank breather mod is common, reduces air pressure in the cases and therefore windage losses are less , total performance oriented bikes like pro stock drag bikes run a vac pump to gain hp, and it must have a fair difference or they would not add the weight of the pump

same sort of reason i cut the bottom of the cyls to match the case cutouts , provides a short path for the air under one piston moving down rapidly and compressing the air to travel to the next rising rapidly creating a low pressure , both costing hp if they were not complimenting each other , creating a vaccuum or lower pressure within the cases means less air to pump around & reduces these parasitic hp losses

used the marble a few times Greeny :) works wonders to stop backfires in aftermarket exhausts

[stunva]

Thanks guys.