crankcase breather

[slipper40]

hi all , i noted in the past that my crankcase breather unit wasn't complete ie the pipe going up to the little pastic box is in place but the pipe to the air box has always been missing, now i m pretty sure this isn't a problem and was only fitted for emission purposes? so i capped the hole in the air box and left it as is , well now i would like to remove the little box and replace with a small filter as i would like to use this space for an alarm , can anyone foresee any probs many thanks steve

[Nickj]

Done that myself, I put the filter up by the top frane rail.
All this does is dump any oil vapour out into the air box so it's burnt. Not sure what the extra box does but it isn't significant in the grand scheme of things,

Apart from not having had any water emulsion in the oil after I fitted the filter there is no noticable difference to anything.

[slipper40]

Done that myself, I put the filter up by the top frane rail.
All this does is dump any oil vapour out into the air box so it's burnt. Not sure what the extra box does but it isn't significant in the grand scheme of things,

Apart from not having had any water emulsion in the oil after I fitted the filter there is no noticable difference to anything.
yeah tis as i guessed thankyou for the feed back :)

[utopia]

Snap.

I removed the tube to the airbox and blanked the hole some time ago, with no noticeable ill effect.
And I too, would like to remove the little plastic tank, and would use the space to store my xena disc lock alarm.
My assumption has been that the little plastic tank acts as a separator, ensuring that excessive oil blown out of the breather can return to the crankcases, to avoid too much oil being dumped in the airbox.
Up to now though, I've left it in place.

I have long since removed a similar plastic tank from my honda dominator though, and simply used a long length of rubber tube from the crankcases to a cheap in-line fuel filter under the seat, and thence to atmosphere. Seems to be fine, though minimal resistance at the filter would give the best crankcase breathing and least pumping power loss, so I may replace it with a k&n at some stage.
I'm not sure that you really need a filter at all, except to keep spiders and earwigs out.

I've not noticed much oil emulsion foam since removing the upper pipe on the monster either.
Funny that, really....cos my logic says that the hot oil vapour is likely to absorb moisture as it condenses in the little plastic tank, which then drains back into the engine, so removing the tank would be the critical thing....but I still have mine and things do nevertheless seem to be somewhat improved.

[Dukedesmo]

The plastic tank is primarily there as a seperator/catch tank that will catch any oil that escapes the crankcase and allow it to separate from the air and settle back down into the engine - it should never get much oil in it but it might as the engine wears (rings) etc or if you pull a prolonged wheelie which can cause the engine oil to flood out the breather.

It can also be used in racing (although larger tanks are normally used for this) as a crankcase 'extension'. By placing the reed valve in the airbox (after the tank) then the tank effectively becomes part of the crankcase volume, for the air that is compressed inside the crankcase to fill - bigger volume = less resistance against the power stroke, so more power. However this only really has any effect at high RPM and so is normally reserved for race bikes (racing 916, 888 etc use a much larger underseat tank and reed valve in the airbox for this purpose).

The reason for the breather ending in the airbox is mainly for emissions purposes as any oil vapour is taken in the intakes and burnt with the fuel but the lower pressure in the airbox also adds a bit of suction helping reduce the crankcase pressure - although this effect is marginal.

The danger of fitting a filter at the crankcase breather is that if your bike does blow oil out the breather then it will go over the back of the bike - on the rear wheel, it may only do this in a prolonged wheelie but that would be a bad time to do so. It will also be gather oil and dirt etc.

My advice is to keep the reed valve and tank but if you want to fit a filter instead then I would suggest, putting it at the end of a long hose (reducing chance of oil escaping) and place it somewhere out of the way of the wheels (incase it does).

[Stafford]

Also worth a read on this subject
http://www.ducati-upnorth.com/tech/breather.php

[Lima071]

I have removed the plastic tanks from my 900ssie and fitted a k and n filter, bolted to the frame.
By feeding the inlet with any pressure from the crank case would reduce any overall pressure loss.
If you can fit a fan to remove the air from the crankcase it can ease the down stroke of the piston, and the next best thing is to fit a k and n as it leaves the crankcase at atmospheric pressure.
https://www.knfilters.co.uk/vent.aspx

[Lima071]

Also worth a read on this subject
http://www.ducati-upnorth.com/tech/breather.php

The link shows where not to fit the filter, as Dukedesmo said, take it away from infront of the rear wheel and as high as you can so that any vapour that condenses in the pipe will drop back in to the crank case.

[utopia]

It can also be used in racing (although larger tanks are normally used for this) as a crankcase 'extension'. By placing the reed valve in the airbox (after the tank) then the tank effectively becomes part of the crankcase volume, for the air that is compressed inside the crankcase to fill - bigger volume = less resistance against the power stroke, so more power.


Yes, I've heard talk of that somewhere, but your explaination is way better than mine would have been.
I've also wondered about fitting some sort of one-way valve in the breather in an attempt to create negative crankcase pressure. From your post, I assume that the reed valve in the std breather does a similar job. I wasn't aware of exactly how that part operated in the std set-up. I'm glad I didn't bother with the valve now. To be honest, I was a bit wary for fear of unexpected consequences, in pursuit of little practical gain.

There was also a little device that popped up a few years ago called the "Intech".
This may have worked in a vaguely similar kind of way, though I never did find any proper information on it, and there were strong rumours that it was snake oil.

[Stafford]

Apart from going the way of the Panigale using a pump to reduce crankcase pressure some racers used to use a plastic tank fitted with the non-return valve under the seat hump (851/888) to effectively increase crankcase volume and reduce pressure. So giving them an extra bit of HP but I'd guess not a lot, but then every little helps at the top end of performance.

[Dukedesmo]

Apart from going the way of the Panigale using a pump to reduce crankcase pressure some racers used to use a plastic tank fitted with the non-return valve under the seat hump (851/888) to effectively increase crankcase volume and reduce pressure. So giving them an extra bit of HP but I'd guess not a lot, but then every little helps at the top end of performance.

I have that setup on my 916; a large tank under the seat with a straight-through big-bore breather valve from the crankcase all connected by large bore hoses and a reed valve in the airbox at the end of the breather system.

In theory it should give a slight horsepower gain - it might add a couple of HP on a full-blown factory race bike. But it does prevent any oil getting onto the rear tyre if the engine should puke it's oil as it's big enough to contain all the engine oil - the standard setup (including the separator tank) can be overwhelmed and oil flood into the airbox.

There's probably not much (if any) gain to be had on an air-cooled Monster? but I plan on using the catch tank (or a bigger one if I can find one) with the reed valve at the very end of the system to replicate, as close as possible this setup, the way I see it there are no disadvantages and possibly some benefit.

Either way beware of the K&N on the crankcase as it can spray oil over your rear tyre...

[Capo]

I fitted a Krank Vent valve at the airbox an removed the valve from the engine connection.

http://www.et-performance.com/index.html

http://i295.photobucket.com/albums/mm143/Tarugo996/aaP1010408.jpg

If you want to get serious about crankcase ventilation some very interesting stuff here

http://bunnbreather.bigblog.com.au/post.do?id=345983