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Breather pressure

theoneandonlymin

Tuned and Synch'ed
GT Contributor
Joined
Oct 28, 2008
Messages
75
Location
somewhere around 82
Just wondering if I am pressuring my crankcase. If I pull my dipstick out there is a fair bit of oil blasting out. If I put my finger on the main crankcase breather that exits the le mans type box there would be very little pressure.
Question arises as I am replacing rear crankcase seal, again, which fairly throws oil into the bell housing.....installed a oil absorbing nappy under the drain hole a while back. But I have time now to throw a seal in.
Cheer's
Min
 
There could be an issue of a stuck flapper in the LeMans breather. While you have the bike apart, check that valve at the top of the large pipe that enters the box from the bottom. Also Guzzi engines hate to be over filled. Most are happy about half way between fill and add marks on the dipstick. Oil should not be coming our of the dipstick hole with the engine off. If it is running, yes, the crank shaft throws oil all over the place due to air movement in the crankcase. What bike are you running as there may be a better venting system than the LeMans type box.
 
Oil level is fine.Extended sump and correct length dipstick for 3 litres of oil. V1000 G5 no air box.

Cheers
Min


I take it you added the sump spacer like the CA II has. Still I wouldn't put more than 2.8L in there. These engines are really good at sloshing oil around. The LeMans type breather is probably the easiest way to go.

Have you done a leak down test to see if the rings are sealing as they should? That could account for increased crankcase pressure.
 
So I borrowed a bench and set to the rear seal today. While I was at it I put a bit of air down the dipstick hole. Breather works fine so it does.

For the last year, 12000miles, I have had an oil( but not water) absorbent cloth suspended below my bell housing catching the oil as it came out. Worked well and needed a nappy change every 500 or so.

After a 40 mile blast home tonight the nappy is dry. Whoop whoop.
Hope this time the seal holds.

Cheers
Min

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I've learned the hard way over the years to fill oil only to the halfway point between the dipstick marks as John suggests. Same for SP and 850T. Filling higher works OK until I cruise at 70 or more, at which point it just ends up blowing it out the breather all over my rear wheel until it reaches the magic halfway point again.

Doesn't come out the rear seal though. I would suggest upgrading to the ball style breather check valve and disable the flapper in the breather box. I think it is intended to maintain some negative pressure in the crankcase whlle the engine is running, helping to pull oil down from the valve gear. A bad breather check could make seal problems worse.
 
Hi, new to guzzi, my 1980 sp1000 café racer has sump extension and has just blown a lot of oil out of breather.
Could someone ease confirm how much oil should be used with deep sump?
Breather system is also a mystery. Running k&ns with no air ox, is there a recommended way to tidy up / refi e breather please?
Cheers, Duncan

Just read what is posted above.
 
Get your helicoil kit out. It will help. Put in 3 liters with a filter change. If you do future oil changes without changing the filter about 2.75 liters should do.
 
You only want one breather check valve, so either the flap type valve or the ball valve - not both. If both are used, they can counteract each other and cause oil to be ejected. If the flap type valve is still in working order, then that is my preference. The port through the flap is over twice the size of the port through the ball valve. If you use the ball valve, then disable the flap type valve.

I use 3 qts. (2.84 liters) exactly and never have any issues with leaking or blowing oil out on healthy engines.
 
Brilliant, will do.
Box looks like new and flap moves freely so I'll go with that and get rid of the ball valve.
All looks good inside engine from what I can see so hopefully this will sort it out and I can get a few miles done.
Thanks a lot, Duncan.


Yes, take out the ball valve, but don't throw it away. It may come in handy some day.
 
If you are sure the oil filter is on tight, just start the engine. Light should go out. I hope the 3 liters includes what you put in the filter. If not it will be over filled.
 
Yes exactly 3 litres including what I put in filter.
How tight is tight?
Tight as poss by hand...
Can't understand why no oil from oil switch hole if pumping round....
Have ordered hiflo filter and was going to drop sump again, check / replace filter before trying again. Obviously don't really want to drain new oil again..


Filter should be tightened hand tight plus 1/4 turn with a filter wrench or to 15Nm.
 
Maybe just cranking it over isn't fast enough to build up pressure, start the bike, but of course if the light dose not go out after 5-10 seconds turn it off and investigate.
 
Keep in mind that the oil pump turns close to engine rpm ( low at cranking speeds) and the pump gears
only move a teaspoon or so with each rotation , so as said above , don't be afraid to start and run for a bit . Peter
 
I don't know why it happens, but sometimes I find it necessary to force oil into the pump and oil circuit by pressurizing the sump. I drill and tap an old oil drain plug and add a schrader valve, block the crankcase breather outlet and pressurize the engine to ~ 5 psi.
 
Couple of things...
It's worth fitting a large jubilee clip around the bottom ridge of your filter with the screw butting up against the solid oil way portion, this prevents the filter ever coming loose.
I ditched the breather hoses from my valve covers on my LM2 and blanked the covers and two small pipes into the breather. I just got fed up with mayo pouring into the heads whenever I took the covers off. I don't believe the breathers from the valve covers do anything. The main crankcase breather is more than good enough.
I did an oil and filter change recently and like you, just turning the motor on the starter didn't put the oil light out.
I just fired up the engine and out it went.
 
Check the hose on top of the engine for cracks under the hose clamp. Common but hard to see. I silicone the gap around the breather pipe, so if the hose splits, the oil runs on the outside of the engine instead of through the bell housing.
There are two other causes besides the main seal for engine oil coming out of the bottom:
1) the two bottom bolts of the main bearing (they need silicone on the threads)
2) cracked rear cap of cam shaft (epoxy fixes it)

Let's hope for a split hose :)
 
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