Crankcase breather question

[bigpup]

Hey fellas, when i turn my key on sometimes before start-up you can hear pressure release. a big fffffffffff comes out. Does that mean my crankcase is not breathing right? or does it just build up pressure after a ride then the next time you start it, it releases built up pressure?

 

[xsjohn]

It has a push of air out as the pistons go down and sucks in as the pistons go up..........and all this is more noticable at low rpm..........as rpm increases the air can't go in an out fast enough so the pressure inside the case begins to become neutral....so less is noticed moving back a forth........and you don't hear or smell all this with the air box on.....and with pods....welcome to the world of sounds and smells............

xsjohn

 

[Sundie]

It also might mean that your rings are done, and you're getting combustion down into the crankcase, which is over pressuring it. Mine used to do this before i replaced the rings.

 

[bigpup]

Thanks guys for the input, Sundie motor is freshly rebuilt from the cases up.

 

[xsjohn]

Gas igniting from a coil firing when you turn the key on.......what else could it be....never head this story....?

xsjohn

 

[malloym]

yea, mine does it all the time... no worries.

 

[xsjohn]

Mine has never has done that and if it did I would wonder if my mixtures were way to rich or if I had a carb problem........rich mixes seem to make these pull harder but too much will wash the cylinders.....for sure.....that's why I went to 8-1 so I could lean it a half a tad and still have a quiet engne that pulls great and sounds good even when it is hot.....some extra air over the cylinders and the timing a bit less than stock does mine well now....

xsjohn

 

[malloym]

I might be too rich. the bike does seem to lag a tad on acceleration. I really need to get it on the dyno for a proper tune.

 

[xsjohn]

If you have more than a 137.5 on any of these you are probably too rich and when on full acceleration the rings can be washed....timing and use of the normal rpm range is something to think about...and what is a dyno going to tell you except max HP at horrendous rpms that you aren't using as you tool down the road.......man I used to build roadracers........which really have nothing to do with street or any of the ole xs's with untrue pressed cranks...(work the mid lowers to mids for these ole things)..and how far you can get down the road reasonably......ah what wouild I know......

I tell my son if you want max HP...join the AF.......

xsjohn