Crankcase Restrictor Found

[sparki]

Hi
I just found this crankcase breather pipe restrictor on my son’s BT50QT-9
It s the 2004 Model. It’s just a small rubber bung with a 2mm hole.

The bung is where the rubber pipe meets with the Air intake pipe before the filter box.

[ally1756]

did it make any difference?

[sparki]

Yeh

I found it when I was trying to see why it wouldn’t idle smoothly,
And yes it has made it run better.
The only reason I can see it being there, is as an air flow restrictor to increase air pressure in the crankcase.

[ally1756]

might give it a try

[Scootin]

Did it smooth out the idle any? my engine has been surging lately.
Have tinkered witht eh fuel/Air mixture & idle speed but no luck

[mii]

Breather in crankcase is something nearly all the 4 strokes have. Unless the pipe is going back to the carb, I'd recommend to keep it shut..

[ally1756]

no u dont wanna close a breather!

[mii]

yeah, but you don't want your oils to be spilling all over the place either..

[Badobsession (the real one)]

I know of a certain person who when servicing a z400 folded the crankcase breather out of the way but forgot about it.
When i (Err i mean the certain person) went up the road with it still blocked the pressure built up and blew the pipe off and soaked the rear tyre in oil
Oil on tyre + corner = crash #crying#

[ally1756]

wow thats not too good

[Badobsession (the real one)]

My excuse is i was only seventeen at the time

[mii]

wonder how long is that pipe..I mean, camcase pressure with these 50cc engines surely can't be that huge problem, possibly the pipe itself is acting up like expansionchamber and even gives some backpressure so the difference between open and closed pipe shouldn't be that big..dunno. If I find that kind of pipe when I strip her down, I'm keeping it intact, since it's not going to the carb (and therefor recycling the oil and lubricating the system, like in big bikes or cars) and with open head will propably cause more problems than solve them.

[mii]

camcase=crankcase. Sleepy ^^

[Mark...]

My breather hangs down oh no, that doesnt sound right.
mii, WTF!!! SHUT UP.

you cant possibly be serious? If you are serious, im sorry.

Breathers breathe air don't they? #dunno#

[Mark...]

[ally1756]

different breather me thinks

[sparki]

Just to confirm to all.

Taking the small rubber restrictor out has made a slight difference.
I does idle a lot smoother now.
I assume because the air is now being supplied to the air filter with a little bit more pressure when the bike is just stood ticking over. When the bike is moving that pressure is naturally supplied by the bike moving through the air.

[mii]

fullthrottle said:

mii, WTF!!! SHUT UP.

Well, that's mature and polite.

Wrong breather, you are looking at the camcase, not the crankcase. Even if I was wrong, there is no reason to be rude, now is there? I'm not saying I'm right, I just feel, the crankcase breather is not supposed to be open. I do hope the current breather pipe itself is acting like a vent, but cutting it open is just stupid, unless the oil is recycled somewhere, like it is in bigger and even smaller 4 strokers. Guess chinese engineers went the easy way on this one; using a pipe as an expansionchamber and not letting the oil come out, vs. filtered crankcase breather pipe, that's connected to the carb which recycles the oil back to the system. First one is very inexpensive and effective compared to the last one, that has many weak points but most of all, costs quite a few euros to build.