New GS1000 member question

[Guest]

Hi Guys,
I have been reading these forums and first "Thank you" to all the members for their help with these vintage bikes.
I just picked up a 1980 GS1000G, I'm in the process of getting it running again. I got my Clymer manual in yesterday which helps!

I found the thread on the "mystery hole" which help me figure out why I'm leaking oil through the bottom as this tube was pumping oil into the starter area. After I removed the starter and cleaned the entire area, I started the GS up again and oil is coming out of this pump/ tube. What is this tube? Should it be plugged in somewhere? Why does it flow more when I rev the GS up? Seems like it should be simple

 

[rphillips]

That is a crankcase vent. First thing is be sure your crankcase isn't over full of oil. checked while on center stand, NOT side stand.

 

[Guest]

It was doing this before the oil change, and it's doing it afterward as well. During my filter and oil change, I only put 3 quarts in. Manual says 3.4.
Maybe this is gear oil overflow? I have not changed it yet, perhaps the last person overfilled it? It's on the center stand as well

 

[rphillips]

Sorry, I shouldn't have just called it a crankcase vent, that's not the name on the parts fische, part # 51, it's called a plug, bLeather, not sure maybe a misprint for bReather & not being shown on the chain dr. models, should be a clue.

 

[Guest]

Thanks rphillips. Good call if it is not shown on the chain models, then it must be gear oil related

 

[Guest]

after further research it is not a secondary gear breather. It is a crankcase vent. Would would be causing the motor to push this out?

Every time I start the bike, within a minute or two oil leaks out of the breather. Seems like there is too much crankcase pressure to leave this plugged. I don't want to start blowing seals. Should this be venting to atmosphere or connected somewhere?

Also would a blown head gasket cause this pressure in the crankcase? I do see some oil coming out of exhaust side, upper head gasket. it's a very slow drip while running.

 

[rphillips]

The crankcase vent should be on top of the valve cover. Appx. 3/8" hose running from a plate on the top center rear of the valve cover to the top center front of the air box. The cam chain tunnel is wide open down into the lower crankcase... Just looked again, only the shaft dr. models have this part.

 

[2BRacing]

Hi Guys,
I have been reading these forums and first "Thank you" to all the members for their help with these vintage bikes.
I just picked up a 1980 GS1000G, I'm in the process of getting it running again. I got my Clymer manual in yesterday which helps!

I found the thread on the "mystery hole" which help me figure out why I'm leaking oil through the bottom as this tube was pumping oil into the starter area. After I removed the starter and cleaned the entire area, I started the GS up again and oil is coming out of this pump/ tube. What is this tube? Should it be plugged in somewhere? Why does it flow more when I rev the GS up? Seems like it should be simple

Your symptoms point to the failure of the oil seals between the crankcase and the secondary gear compartment, allowing that compartment to fill up with engine oil. The excess is pushed out through the breather and the mystery hole.

There are quite a few old threads describing the problem "Mystery hole oil seepage".

To positively confirm the above, you should drain the secondary gear oil and measure the volume of oil that came out. If it is much more than the specified volume, that confirms engine oil is going past the seals into that compartment. Another clue is that the colour of the oil will be dark if the engine oil is not new, instead of light-coloured gear oil.

 

[Brendan W]

2BRacing took the words out of my mouth.
The oil level in my bike is always well over the level mark when I change and the dark colour says engine oil getting in.
I'm not going anywhere near it anytime soon. I change the gear oil regularly and at my mileage that's good enough for me.
I also recall an old thread. Motor taken out, flipped and the lower crank case removed. All done in a weekend with help from a friend if I recall correctly.

 

[rphillips]

This is interesting, I've never been inside one of these. There should be no pressure pushing the motor oil through that seal, just seeping (oozing) through into that compartment (tank). With only the eng. running & the gears just sitting there, not even turning, what would push the eng. oil & gear oil mixture up & out that vent on top of the case? May see it if gears were turning & kind'f slinging the oil, but... Very interesting.

 

[Guest]

This is interesting, I've never been inside one of these. There should be no pressure pushing the motor oil through that seal, just seeping (oozing) through into that compartment (tank). With only the eng. running & the gears just sitting there, not even turning, what would push the eng. oil & gear oil mixture up & out that vent on top of the case? May see it if gears were turning & kind'f slinging the oil, but... Very interesting.

Thank you all for responding, I really appreciate all the help from 2BRacing, Brendan & rphillips. When you say "may I see the gears" to which are you implying to see?


See video attached

https://photos.app.goo.gl/ZdD7eH8qWqWccmfeA

 

[Brendan W]

That's a serious leak.
Given that the original function of that vent was to prevent the seals in the secondary being pressurised and there is clearly an internal 'vent' to the crankcase, maybe it's not needed anymore?
Thinking on my feet here but blocking that vent may reduce the flow of crankcase gas and engine oil into the secondary box.
First thing I would do is open the level screw in the box and drain any excess. Then run the motor and see what if any comes out the breather hose and when it cools down check the level in the box again.

 

[Guest]

That's a serious leak.
Given that the original function of that vent was to prevent the seals in the secondary being pressurised and there is clearly an internal 'vent' to the crankcase, maybe it's not needed anymore?
Thinking on my feet here but blocking that vent may reduce the flow of crankcase gas and engine oil into the secondary box.
First thing I would do is open the level screw in the box and drain any excess. Then run the motor and see what if any comes out the breather hose and when it cools down check the level in the box again.

Thank you Brendan, I will try that as well. I found this youtube where a guy refers to that plug as gear box vent

https://www.youtube.com/watch?v=zLkXXII28yA 3:40 sec

 

[2BRacing]

2BRacing took the words out of my mouth.
The oil level in my bike is always well over the level mark when I change and the dark colour says engine oil getting in.
I'm not going anywhere near it anytime soon. I change the gear oil regularly and at my mileage that's good enough for me.
I also recall an old thread. Motor taken out, flipped and the lower crank case removed. All done in a weekend with help from a friend if I recall correctly.

This old thread detailed the job with photos (hosted on Photobucket) that still show up on my side. I hope it is of help to the OP.

Mystery hole oil seepage - seal between secondary gear compartment - The GSResources Forums

 

[Guest]

Guys this is it, finally I have my answer. Thank you all. Your link is exactly what this bike is doing. Question what if I piped the overflow back into the engine? What harm would that cause?

 

[rphillips]

I didn't look at the link yet but it seems if you run that oil back over in the crankcase, eventually you will be running the gears in motor oil. If the bike has been doing this for a while, the gear oil is already diluted, or displaced, with motor oil

 

[Brendan W]

Guys this is it, finally I have my answer. Thank you all. Your link is exactly what this bike is doing. Question what if I piped the overflow back into the engine? What harm would that cause?

You could end up diluting the gear oil to the point of frustrating the designers decision that those particular gears need heavier oil. There have been a few cases on here where that box locked up underway. I don't recall any smoking gun but that seal failure is surely up there as a possible contributory cause.
An interim measure might be to block the vent and reduce the flow of engine oil and gas into and through the box?
I do only a few thousand a year and change the oil every spring. It's always over full, as I said earlier, but not by too much. You case seems to be in a different league.

 

[Brendan W]

This old thread detailed the job with photos (hosted on Photobucket) that still show up on my side. I hope it is of help to the OP.

Mystery hole oil seepage - seal between secondary gear compartment - The GSResources Forums

Quite a find however you did it.
By the powers vested in me I hereby appoint you chief custodian of records

 

[Grimly]

The original engine in my 79 850 had developed a leak between engine and bevel, but it soldiered on for ages like that.
I knew that some other shafty bikes were (by design) running their front bevels in engine oil, so it didn't particularly bother me.
I just kept a careful eye on levels.

 

[Guest]

Guys I have a favor since I am somewhat new to the GS bike. Could the group try and help me with a parts list for that rebuild thread?

• I need to know which gaskets, O-Rings etc that I will need. Unfortunately, it is not listed, thus I want to make sure I have all the parts before I remove the engine.

Thank you all in advance, Love you guys.
JA