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Steel hose in oil cap, thoughts?

  • Thread starter Thread starter Guest
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Looks to me like it comes from the engine breather fitting on top of the valve cover. Normally, a simple rubber hose goes from there to the airbox, and then to a drain to ground (said drain tube often capped so as not to let this oil drip onto the road directly in front of the rear tire :eek:), to allow excess oil vapor a place to go. Seems you have a fancy braided steel hose the returns this oil to the oil reservoir instead. I can’t think of any harm it would do. More experienced wrenches will tell you, if so. But I can’t really imagine a benefit of it either. At least that’s what I think.

oh, by the way, beautiful bike.
 
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Hum, never seen that before. It's got a big bore kit installed so maybe the previous owner felt the engine needed more crankcase breathing. Where does the hose lead?
 
Rich82GS750TZ said:
Looks to me like it comes from the engine breather fitting on top of the valve cover. Normally, a simple rubber hose goes from there to the airbox, and then to a drain to ground (said drain tube often capped so as not to let this oil drip onto the road directly in front of the rear tire :eek:), to allow excess oil vapor a place to go. Seems you have a fancy braided steel hose the returns this oil to the oil reservoir instead. I can’t think of any harm it would do. More experienced wrenches will tell you, if so. But I can’t really imagine a benefit of it either. At least that’s what I think.

oh, by the way, beautiful bike.
Click to expand...

Good point, Rich. The owner says it's recommended for big bore and tuned engines, likely no benefit to regular set up. Btw, that thing has over 99,000 on the odo :)
 
I don't recommend adding a breather from the oil filler cap.

I'd rebuilt a GSXR1100 which had one fitted. We ran it on a dyno to sort a couple of things - and it leaked from that breather.
I blocked it off and we repeated the run. It picked up around 3HP from 6500rpm upwards.
None of us could work out why it was so - so we repeated it with the breather open again. Lost those 3HP again.

The GSX and GSXR have similar crankcase volumes and a standard breather from the top of the cam cover, Pretty comparable IMO.
 
Never seen that hose before, but that is one proper restomod 11E! Love the front end. Is it an '81 or '80?
 
Was there a difference from "80" to "81" models other than the colors & date on registration papers?
 
rphillips said:
Was there a difference from "80" to "81" models other than the colors & date on registration papers?
Click to expand...

I'd like to know that also. I'm guessing there must have been some improvements, as 1980 was the introduction year.
 
Inadequate crankcase ventilation leads to a pressurized crankcase resulting in "ring flutter", where the rings bounce in their slots, killing ring seal.
Not really a problem with a stock GS with 0.125" thick rings. Modern rings are much thinner, and much more flexible, usually about 0.040" thick.

Top fuelers, and other motors that get regular teardowns will run a vacuum pump, keeping negative pressure in the crankcase. The idea being the vacuum sucks the rings down and holds them in the bottom of the ring slot.
The rings don't last very long at negative 3 bar.
 
bitzz said:
Inadequate crankcase ventilation leads to a pressurized crankcase resulting in "ring flutter", where the rings bounce in their slots, killing ring seal.
Not really a problem with a stock GS with 0.125" thick rings. Modern rings are much thinner, and much more flexible, usually about 0.040" thick.

Top fuelers, and other motors that get regular teardowns will run a vacuum pump, keeping negative pressure in the crankcase. The idea being the vacuum sucks the rings down and holds them in the bottom of the ring slot.
The rings don't last very long at negative 3 bar.
Click to expand...

While I don't disagree, you may want to check your conversion tables, LOL. Most GS rings are 1.25mm thick. Not 1/8inch. Say .050in approx.
 
bitzz said:
Inadequate crankcase ventilation leads to a pressurized crankcase resulting in "ring flutter", where the rings bounce in their slots, killing ring seal.
Not really a problem with a stock GS with 0.125" thick rings. Modern rings are much thinner, and much more flexible, usually about 0.040" thick.

Top fuelers, and other motors that get regular teardowns will run a vacuum pump, keeping negative pressure in the crankcase. The idea being the vacuum sucks the rings down and holds them in the bottom of the ring slot.
The rings don't last very long at negative 3 bar.
Click to expand...

Thinking about this, how do you measure to a figure like negative 3br? I understood that once a vacuum is achieved that's it there would be nothing left to measure and that would be zero.
I imagine that the rings suffer because the vacuum lowers the boiling temperature point so that the efficiency of the oil is changed massively, rings rely on mist to lubricate and a vacuum would surely affect that especially in a hot engine?
Just asking, not challenging.
The ring flutter is interesting
 
Sure you guys are not overthinking this?
I have one on the 850 so I don't have to bend over to top off the oil.
The old knees aren't what they used to be.
 
 
I've been advised that the big bore kit (1100 cc high compression Wiseco pistons) may be causing the gaskets on my GS1000 engine to not seal correctly due to higher than stock crankcase pressures. I've been blowing gaskets & seals left and right since getting the bike back on the road after a number of years in storage, leading to oil leaks. The stock breather may be inadequate for this application.


So, one of these clutch cover mounted crankcase breathers is now on its way. Now need to source and mount an oil catch can....or maybe just put a filter on the end of the braided hose. We'll see.

k6XKHaM.jpg
 
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You're putting at patch on it rather than sorting the problem.
If you're getting high crankcase pressures I'd look at the rings. If it's been laid up for some time you could have had rust on the bores.

Wiseco big bores are not known for giving problems. None of the many I've done have had this problem.
 
80GS1000 said:
So, one of these clutch cover mounted crankcase breathers is now on its way. Now need to source and mount an oil catch can....or maybe just put a filter on the end of the braided hose. We'll see.
Click to expand...

Might get one as well, since I'm riding high speed highways most of the time it probably wouldn't hurt. Also curious what to do with the other end of the hose, if it's possible to connect it to top end breather or just bolt it up.
 
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