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Breather pressure

Discussion in 'Loop & Tonti' started by theoneandonlymin, Apr 20, 2017.

  1. theoneandonlymin

    theoneandonlymin Tuned and Synch'ed GT Contributor

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    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
     
  2. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    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.
     
  3. theoneandonlymin

    theoneandonlymin Tuned and Synch'ed GT Contributor

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    Oil level is fine.Extended sump and correct length dipstick for 3 litres of oil. V1000 G5 no air box.

    Cheers
    Min
     
  4. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    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.
     
  5. theoneandonlymin

    theoneandonlymin Tuned and Synch'ed GT Contributor

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    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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    Nordicnorm, Sheepdog and Hydrolastic like this.
  6. T Bill

    T Bill Tuned and Synch'ed GT Contributor

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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.
     
    thomas likes this.
  7. Duncan1964

    Duncan1964 Just got it firing!

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  8. Duncan1964

    Duncan1964 Just got it firing!

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    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
     
  9. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    Just read what is posted above.
     
  10. Duncan1964

    Duncan1964 Just got it firing!

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    Thanks for the reply.
    I've drained / removed sump and all pipes / aftermarket catch tank and measured 3.3 litres AFTER bike had blown about 500ml to 1 litre out of overflow!
    Also noticed that my breather has flap valve in box AND inline ball valve in big tube.
    Both seem to work ok.
    When oil blew out I had just removed valve cover breathes and looped thin pipe to top of breather which seemed to cause oil leak (presumably massive pressure with excess oil, must have been nearly 4 litres in there).
    My 160mm long dipstick is marked at about 50,85,110mm.
    Now intend to refit sump with new gaskets and filter and try either 2.8 or 3 litres oil.
    Do I need to refit valve cover breather please? (Will need to helicoil as bit of thread missing where banjo bolt attaches).
    Only had bike a few weeks and not had chance to ride it properly yet!
    Cheers,Duncan.
     
  11. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    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.
     
  12. Duncan1964

    Duncan1964 Just got it firing!

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    Will do, thanks a lot.
    Do you think I should 'disable' the breather flap and just use ball valve?
    Fairly sure previous owner thought sump extension was to get more oil capacity hence the overfill. Presume they have had same trouble with big catch tank etc.
    I'm going to leave catch tank off and run breather pipe right down to end of swinging arm (shaft side) then fit 90 degree bend and short pipe under silencer to try and keep any oil away from tyre / brake.
    Did this on my old Norton and Triumph in the past and worked quite well.
    Thanks,Duncan.
     
  13. Amboman

    Amboman Cruisin' Guzzisti

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    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.
     
  14. Duncan1964

    Duncan1964 Just got it firing!

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    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.
     
  15. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    Yes, take out the ball valve, but don't throw it away. It may come in handy some day.
     
  16. Duncan1964

    Duncan1964 Just got it firing!

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    Valve cover breathers back in, sump cleaned out, gaskets, filter, new oil pipes ordered.
    Hopefully all systems go later this week.
     
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  17. Duncan1964

    Duncan1964 Just got it firing!

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    New oil & filter, now oil light won't go out!
    3 litres of 20/50 classic oil, new UFI filter (prefilled with oil), new sump gaskets.
    All new breather pipes with hose clips.
    Turned over for ages with plug leads off but oil light stays on.
    Took sender out and turned over again but no oil coming out of switch hole.
    Help please!
    I've only ridden this bike about 2 miles in total so far and its driving me mad!
    Cheers,Duncan. 20201201_153316.jpg
     
  18. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    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.
     
  19. Duncan1964

    Duncan1964 Just got it firing!

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    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..
     
  20. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    Filter should be tightened hand tight plus 1/4 turn with a filter wrench or to 15Nm.
     

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