« previous next »
Pages: [1]   Go Down

Author Topic: Oil leaking from overflow tube  (Read 8853 times)

0 Members and 1 Guest are viewing this topic.

EverettShadowbrook

  • Guest
Oil leaking from overflow tube
« on: May 30, 2009, 08:49:31 am »
Hi All,

Another Q for everyone about my beater. Have a 1976 cb750 that I recently aquired. Oil is leaking fairly substantially from the overflow tube. I changed the oil two weeks ago and after driving for about 50 miles the oil has almost completely dripped out (only while riding). Obviously not normal. What could be causing this? Thanks
Logged

Offline MCRider

  • Such is the life of a
  • Really Old Timer ...
  • *******
  • Posts: 14,376
  • Today's Lesson: One good turn deserves another.
Re: Oil leaking from overflow tube
« Reply #1 on: May 30, 2009, 09:23:58 am »
Quote from: EverettShadowbrook on May 30, 2009, 08:49:31 am
Hi All,

Another Q for everyone about my beater. Have a 1976 cb750 that I recently aquired. Oil is leaking fairly substantially from the overflow tube. I changed the oil two weeks ago and after driving for about 50 miles the oil has almost completely dripped out (only while riding). Obviously not normal. What could be causing this? Thanks

Define "overfrlow tube".  From the oil tank. The engine? Whereabouts?

Is this a new problem? Have you ever put significant (200+) miles on this without losing all the oil? Or has it always been like this?
Logged
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

EverettShadowbrook

  • Guest
Re: Oil leaking from overflow tube
« Reply #2 on: May 30, 2009, 09:34:14 am »
Its coming from the oil tanks overflow.

I haven't had a chance to put a significant amount of miles on the bike yet as I have just acquired. At first I thought I overfilled with oil slightly, but obviously not the case considering it has almost completely drained after a few short rides 50 mile total.
Logged

Offline mystic_1

  • Really Old Timer ...
  • *******
  • Posts: 6,071
  • 1970 CB750K
Re: Oil leaking from overflow tube
« Reply #3 on: May 30, 2009, 09:39:49 am »
I wasn't aware that the oil tank has an overflow?

There's a line that comes from the oil vapor separator on the back of the tank, this should connect to a fitting at the rear of the engine, just in front of the swingarm pivot.  This returns oil to the engine from the separator.

mystic_1
Logged
"A ship in harbor is safe, but that is not what ships are built for."
- John Augustus Shedd

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0

EverettShadowbrook

  • Guest
Re: Oil leaking from overflow tube
« Reply #4 on: May 30, 2009, 10:05:18 am »
I believe you are correct. The tube is coming out from just in front of the swingarm. looks like its coming from the oil tank. Def behind the engine.

HELP!
Logged

Offline mystic_1

  • Really Old Timer ...
  • *******
  • Posts: 6,071
  • 1970 CB750K
Re: Oil leaking from overflow tube
« Reply #5 on: May 30, 2009, 10:21:26 am »
Again, the hose from the back of the oil tank is supposed to plug into a fitting on the back of the engine.

mystic_1
Logged
"A ship in harbor is safe, but that is not what ships are built for."
- John Augustus Shedd

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0

EverettShadowbrook

  • Guest
Re: Oil leaking from overflow tube
« Reply #6 on: May 30, 2009, 10:27:44 am »
Ok. So there isn't supposed to be a hose hanging down. Maybe this is disconnected - is that what you are getting at?
Logged

Offline MCRider

  • Such is the life of a
  • Really Old Timer ...
  • *******
  • Posts: 14,376
  • Today's Lesson: One good turn deserves another.
Re: Oil leaking from overflow tube
« Reply #7 on: May 30, 2009, 10:29:30 am »
Quote from: mystic_1 on May 30, 2009, 09:39:49 am
I wasn't aware that the oil tank has an overflow?

There's a line that comes from the oil vapor separator on the back of the tank, this should connect to a fitting at the rear of the engine, just in front of the swingarm pivot.  This returns oil to the engine from the separator.

mystic_1
Thats what I was fishing for. Didn't think there were any open hoses on a 76. My K2 tank does have a breather hose open to the atmosphere.
Logged
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline MCRider

  • Such is the life of a
  • Really Old Timer ...
  • *******
  • Posts: 14,376
  • Today's Lesson: One good turn deserves another.
Re: Oil leaking from overflow tube
« Reply #8 on: May 30, 2009, 10:30:52 am »
Quote from: EverettShadowbrook on May 30, 2009, 10:27:44 am
Ok. So there isn't supposed to be a hose hanging down. Maybe this is disconnected - is that what you are getting at?
I think so, but Mystic may be more familiar.
Logged
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline MCRider

  • Such is the life of a
  • Really Old Timer ...
  • *******
  • Posts: 14,376
  • Today's Lesson: One good turn deserves another.
Re: Oil leaking from overflow tube
« Reply #9 on: May 30, 2009, 10:32:59 am »
Quote from: EverettShadowbrook on May 30, 2009, 10:05:18 am
I believe you are correct. The tube is coming out from just in front of the swingarm. looks like its coming from the oil tank. Def behind the engine.

HELP!
"behind the engine" in this case is down low, right in front of the swingarm, but still part of the engine cases itself, actually at the rear of the transmission, there is a spigot for a hose.
Logged
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline mystic_1

  • Really Old Timer ...
  • *******
  • Posts: 6,071
  • 1970 CB750K
Re: Oil leaking from overflow tube
« Reply #10 on: May 30, 2009, 10:58:00 am »
Quote from: MCRider on May 30, 2009, 10:29:30 am
Quote from: mystic_1 on May 30, 2009, 09:39:49 am
I wasn't aware that the oil tank has an overflow?

There's a line that comes from the oil vapor separator on the back of the tank, this should connect to a fitting at the rear of the engine, just in front of the swingarm pivot.  This returns oil to the engine from the separator.

mystic_1
Thats what I was fishing for. Didn't think there were any open hoses on a 76. My K2 tank does have a breather hose open to the atmosphere.


Yup, earlier tanks had a larger diameter vent tube that hangs open, I believe in later models this gets plumbed into the airbox to recycle the vapors?  Liquid oil should not come out of this vent tube in any quantity.  The other, smaller line on the tank returns oil to the engine.  Sounds like this one has come disconnected.

mystic_1
Logged
"A ship in harbor is safe, but that is not what ships are built for."
- John Augustus Shedd

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0

EverettShadowbrook

  • Guest
Re: Oil leaking from overflow tube
« Reply #11 on: May 30, 2009, 10:58:16 am »
Well. You guys are right! Thanks. Two open hoses hanging down near the swing arm. Obviously the cause of the oil leaks. Duh. Its pretty tight in there but will try to get in and connect the hoses. Thanks!
Logged

Offline Johnie

  • Really Old Timer ...
  • *******
  • Posts: 8,509
Re: Oil leaking from overflow tube
« Reply #12 on: May 30, 2009, 11:03:53 am »
That usually does not come off under normal use.  You may want to secure it with something.  Could be disasterous at high speed to dump that oil on your back tire.  Maybe it is just so loose from age and expansion.
Logged
1970 CB750K0 - Candy Ruby Red
1973 CB750K3 - Candy Bacchus Olive or Sunflake Orange
1970 Chevy Chevelle SS396 - Cortez Silver
1976 GL1000 sulphur yellow (current project)

Oshkosh, WI  USA

Offline MCRider

  • Such is the life of a
  • Really Old Timer ...
  • *******
  • Posts: 14,376
  • Today's Lesson: One good turn deserves another.
Re: Oil leaking from overflow tube
« Reply #13 on: May 30, 2009, 11:55:28 am »
Quote from: EverettShadowbrook on May 30, 2009, 10:58:16 am
Well. You guys are right! Thanks. Two open hoses hanging down near the swing arm. Obviously the cause of the oil leaks. Duh. Its pretty tight in there but will try to get in and connect the hoses. Thanks!
As Johnie says, should never come off in regular use.

Two hoses? Big one from cam/valve cover? That's a breather that goes to the airbox I think. No quantity of oil could come out. THey used to be open to the atmosphere?

A smaller diameter one goes from the tranny to the oil tank. Still a type of breather, but with actual oil in it.

Nice if someone else would confirm that.
Logged
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

EverettShadowbrook

  • Guest
Re: Oil leaking from overflow tube
« Reply #14 on: May 30, 2009, 04:37:41 pm »
Ok here is what I've got going on. After further inspection there is actually 3 hoses unconnected down there (See Pics). Which hose goes where? Which one is the breather hose? Looked at the shop manual and couldn't find any details.

Also in the other pic the oil tank looks to have an area to accept a hose. Which one goes there? Thanks everyone.
Logged

EverettShadowbrook

  • Guest
Re: Oil leaking from overflow tube
« Reply #15 on: May 30, 2009, 11:01:29 pm »
bumping it up. Hope no one minds. Pics posted. Help me with routing! thanks
Logged

fuzzybutt

  • Guest
Re: Oil leaking from overflow tube
« Reply #16 on: May 31, 2009, 12:41:36 am »
Quote from: Johnie on May 30, 2009, 11:03:53 am
That usually does not come off under normal use.  You may want to secure it with something.  Could be disasterous at high speed to dump that oil on your back tire.  Maybe it is just so loose from age and expansion.


found that out the hard way, lucky i was only going about 20mph when the back end swapped positions with the front and and put me ass over teakettle :D
Logged

Offline CB750F2

  • Hot Shot
  • ***
  • Posts: 645
  • Pat's first Honda 750 F2
Re: Oil leaking from overflow tube
« Reply #17 on: May 31, 2009, 03:17:36 am »
So you have three hoses. One should go from the rear of the oil tank to the rear ofthe transmission - short hose. One should go from the breather connection at the rear of the valve cover, along the RH side of the frame down to a position just inside the brake pedal pivot. The other tube you have is probably the breather tube for the fuel tank. It should hang with the oil breather tube.
The above assumes that you don't have a breather device fitted to your bike. If it has it will be hanging underneath the battery box and the breather tube from the valve cover needs to be routed to this device. You need to get hold of the correct manual for your model bike to see and understand how it all works. Pat
Logged
Regards
Pat from Australia

Offline Ace

  • Hot Shot
  • ***
  • Posts: 336
Re: Oil leaking from overflow tube
« Reply #18 on: May 31, 2009, 06:01:50 am »
When you changed the oil, did you change the oil filter?  If you did, did you put the spring on correctly?  So in order it would go - front of engine - oil filter - metal washer - spring - oil filter housing with the bolt through the middle.  If the spring is on so it sits against the front of the engine, this may cause some problems for oil feeding and maybe pressure or something to have it come out of the tank breather and on the back wheel.  It might be worth checking if you are not sure.
Logged
1971 CB750 K1 - Sold
1978 CB750 F2 Supersport - Sold
1981 CB900 Bol d'or - Sold
2006 CBR1100 XX Super Blackbird - Sold

Offline Gordon

  • Global Moderator
  • Really Old Timer ...
  • *****
  • Posts: 12,114
  • 750K1, 550K2
Re: Oil leaking from overflow tube
« Reply #19 on: May 31, 2009, 07:56:48 am »
Putting the spring on the wrong end of the filter won't cause pressure build-up, it will just make all the oil bypass the filter.   
Logged

Offline Ace

  • Hot Shot
  • ***
  • Posts: 336
Re: Oil leaking from overflow tube
« Reply #20 on: May 31, 2009, 03:02:29 pm »
Ok then, no pressure build up from filter, glad it wasn't that.  It may be possible to get blocked oil passageways from particles that the oil filter should be filtering out.  Just a thought for other readers.
Logged
1971 CB750 K1 - Sold
1978 CB750 F2 Supersport - Sold
1981 CB900 Bol d'or - Sold
2006 CBR1100 XX Super Blackbird - Sold
Pages: [1]   Go Up
« previous next »