UK Monster Owners Club Forum » .: Technical :. » Engines, Clutch, Gears » Crankcase breather removal.

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Old 16-05-2020, 08:42 PM   #16
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this is the corse breather for 748/9x6 built onto the seat undertray

it’s well over 3 litres (the stock ‘splitter’ on a Monster is a bit under 1 litre) it essentially fills the seat hump.

It breathes through a block on the crankcase with no reed valve (restriction).
The outlet pipe then runs to the airbox, where a reed valve block lives to stop air being sucked back in, you can see that on the left, just behind the rear throttle body in pic.2
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Old 16-05-2020, 09:20 PM   #17
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Quote:
Originally Posted by 350TSS View Post
What I understand from the article is that the most inefficient engine as far as pumping losses are concerned is a single cylinder...

...A 90 degree V twin should be somewhere between the single and the 180-degree twin - towards the single end of the spectrum because of the unequal firing order.
Interestingly, (again for desmo-nerds!), I remember reading that the 1199 superquadro motor incorporated a pump to tackle this phenomenon.

From the Ducati press release...

"The pump is driven by the main oil pump shaft and effectively maintains constant vacuum in the crankcase area below the pistons, reducing atmospheric resistance during the down- stroke of the piston and controlling the internal “breathing” of the engine."



Apparently, the pump is an oversized oil scavenge pump which removes much of the air as well as the oil that's drained back into the crankcase. It scavenges air from beneath the pistons and minimises pumping losses. (The pressure is reduced by around 0.7 to 0.8 bar.)

I don't know whether this system was used on any other motors or models.
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Old 17-05-2020, 01:01 PM   #18
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Originally Posted by 350TSS View Post
Thanks, Luddite
What I understand from the article is that the most inefficient engine as far as pumping losses are concerned is a single cylinder. A four-cylinder (or V8), provided the crankcase is unrestricted for movement of pressure within the crankcase has very few pumping losses other than moving the air from one part of the crankcase to the other. A 360-degree twin is essentially the same as a single and a 180-degree twin better but not as good as a four-cylinder.
A 90 degree V twin should be somewhere between the single and the 180-degree twin - towards the single end of the spectrum because of the unequal firing order.
So for maximum bhp efficiency on a V twin, you need the biggest unrestricted breather pipe venting the crankcase to the atmosphere.
You need to stop crud entering the crankcase so the outlet should have some sort of one-way filter and ideally you want to return the oil in suspension with the crankcase pressure exhaust air to be returned to the crankcase. Control of emissions would be a "Californian" (and manufacturer) concern to most legislators but to petrol heads, let's just maximise horsepower. Any oil mist expelled would obviously need to be kept away from the black rubber rings that keep us on two wheels.
If the piston rings are a good fit in the bore and the valve seals are good it sees to be a good plan to de-restrict the breather of reed valves and let the engine breathe rather than wheeze through a 20mm bore pipe/read valve and potentially choke on its own emissions.
I think from what I understand, it's beneficial to retain the reed valve somewhere in the system in order to maintain negative crankcase pressure. The Corsa setup still has this but upstream of a larger expansion chamber and Luddites air pump does the same thing.
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Old 25-05-2020, 07:40 AM   #19
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While I was rummaging through some boxes looking for the old breather box and hoses I came across some NOS DP breather valves which I had forgot I had:-



After I had decided which colour to use. I set about removing all the gubbins required to get access to the valve.

Fortunately I had already installed quick release fuel couplings so it was fairly straightforward, the tank could stay on and I just had to unplug the brake light connector and move the brake reservoir out of the way to give a bit more room for maneuvering, as it's really tight in there.



There's no room to get a spanner in there to get it undone and it was too tight to undo by hand. I was about to give up and then remembered I had bought some rubber strap wrenches, of the type used to undo jar lids and such.

https://www.ebay.co.uk/itm/500mm-Uni...M8amCLhnv6Ij4w

These are made for this job, it came undone straightaway and was replaced with the new DP valve. I decided that the gold one looked better than the silver one.



I decided against using any sealant on it for now as the plastic ones are prone to leak a bit of oil and I noticed the one on mine had an oring. So will have to see how it fares, with some miles on it.

Anyway all buttoned back up, As soon as the correct hose clips arrive, I just need to fit the new hose and filter and decide where it can be routed that is not going to spray oil mist on the back tyre.

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Old 31-05-2020, 05:54 PM   #20
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I've now routed some hose through from the valve up and backwards into the bike in a similar fashion to the original setup.



And cleaned and re-oiled the K&N filter: -



The only issue now is how to fix the thing to the bike. Someone posted before about doing something similar and making a bracket and there was a picture, but I'd be damned if I can find the post now!
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