Author Topic: What the???? Amazing vanishing oil trick.....sort of (Read 4022 times)

BlackMax · « **on:** July 10, 2009, 03:17:45 PM »

UPDATE!!

Uh, so it keeps pulling oil out of the side tank, until the tank is empty and the oil light comes on. Well, as I added oil, sure enough, OIL STARTED COMING OUT OF THE CRANK VENT (lower)!!!! So, the case is overfilled with oil, but the side case is empty and the oil light is on (I guess the light is triggered due to low pressure??). WTF?

? What is going on? What can I do to fix this?

Ok, this one's weird......I got my bike back, with rebuilt engine. I drove it a bit and there were some problems. I decided to check the oil, as the dummy light was on (but I figured it was just broken). Well, the reservoir was EMPTY. uh oh. So, I added 1 qt of oil. I ran it a bit.....again, red light and EMPTY. I added another 2 quarts of oil while running the engine......it ran the reservoir EMPTY angain!!! I now added ANOTHER 1/2 qt. of oil, for a total of 3 1/2 quarts ADDED to whatever was in there to begin with (if any). The tank is again EMPTY and the red light has come back on.

Now, I read that they take about 3.1 qts of oil, total. How is it that I have ADDED 3 1/2 qts and the tank is empty and the light comes back on. How is this possible? Where is it going?

Thoughts:

1) perhaps the '78 CB750 (f2 black motor) takes more oil than I think??

or

2) The oil is pumping into the crank case and simply overfilling for some reason?

Very confused.......

Can someone help me out? I hesitate to add any more oil to the crank case as I expect straight oil to come spraying out of the breather at any moment.

lrutt · « **Reply #1 on:** July 10, 2009, 03:24:33 PM »

if the engine was totally rebuilt and no oil put in it will take almost 4 qts to get everything topped off. Sounds like it didn't have any in it to start with.

I don't think I've ever gotten buy with just 3.1 qts on an oil change in either of mine.

Inkscars · « **Reply #2 on:** July 10, 2009, 03:30:20 PM »

On a lighter note, if it were a harley, You woulda thrown a rod already.

BlackMax · « **Reply #3 on:** July 10, 2009, 03:37:46 PM »

As mentioned in the update, it looks like oil is being pulled from the side tank, into the crank case, and won't stop! Oil ended up coming out (lots) of the crank vent!!!! So, for whatever reason, oil won't stop pumping from the reservoir to the case!!!

What is wrong? What can be done? How did this happen??

mlinder · « **Reply #4 on:** July 10, 2009, 03:48:03 PM »

Sounds like oil is not making it up the return hose to the oil tank.

UJM · « **Reply #5 on:** July 10, 2009, 04:30:42 PM »

On my 75 3 quarts seems to do the trick

MCRider · « **Reply #6 on:** July 10, 2009, 04:41:26 PM »

There is no "lower" crankcase vent that should be open to the atmosphere. You mention in your first post that oil is coming out of the lower crrankcase vent.

If this is still happening, the oil line that goes from that "lower" crankcase vent is supposed to be connested to the oil tank and yours is either gone or disconnected.

Where has all that oil you've been pouring in gone? Your back tire?

To answer some other questions, if the tank is emptying, the anti - sump valve in the oil pump may not be working. But the oil will stay in the engine, it should not be coming out as there should be a hose on that thing to the oil tank

Finally anything between 3 and 4 quarts total is fine. 3.4 exactly comes to mind. You have bigger problems.

MCRider · « **Reply #7 on:** July 10, 2009, 04:45:53 PM »

Once you get that hose back on the lower vent, then see if it stops wet-sumping. If not, then its the check valve in the oil pump.

Patrick · « **Reply #8 on:** July 10, 2009, 04:49:25 PM »

Or the screen on the bottom of the oil pump. If that gets clogged the pump can't draw oil into the pump. Easily checked if you pull the oil pan.

BlackMax · « **Reply #9 on:** July 10, 2009, 05:06:15 PM »

Okay folks.....here are the updates:

1) when I said "lower" crank vent....I simply meant the crank vent, as differentiated from the valve cover vent/breather. My bad choice of wording. But, it is open to the air....probably should be filtered...but that's a different story. In this case, glad it wasn't.

2) I drained the oil back out of the case. WOW

It was about 2 gallons, no joke.

3) Let me run this by you- I'm probably out in left field on this, and the comment by MCRIDER about the pump check valve seems a likely suspect....but remember, I was doing all this oil checking and filling A) with the engine idling; and, B) with the cap to the oil reservoir REMOVED (so I could watch the oil level as I was filling). Now, is it possible that those things could have created the problem by themselves? Could the fact that the cap was removed while running the engine, created a no pressure situation that prevented enough pressure in the case to force oil to return to the side-tank AND create a low pressure reading (thus the dummy light)

mlinder · « **Reply #10 on:** July 10, 2009, 05:15:08 PM »

Nope, prolly not.

Oil isn't returning to the tank. Need to find out why.

GammaFlat · « **Reply #11 on:** July 10, 2009, 05:22:49 PM »

I thought I read where somebody put the oil lines on backward once....?

BlackMax · « **Reply #12 on:** July 10, 2009, 05:31:41 PM »

Quote from: mlinder on July 10, 2009, 05:15:08 PM

Nope, prolly not.

Oil isn't returning to the tank. Need to find out why.

any thoughts on:

1) list of possible reasons oil would not be returning to the tank

2) which line is out and which is in?

MCRider · « **Reply #13 on:** July 10, 2009, 05:43:49 PM »

Quote from: BlackMax on July 10, 2009, 05:06:15 PM

Okay folks.....here are the updates:

1) when I said "lower" crank vent....I simply meant the crank vent, as differentiated from the valve cover vent/breather. My bad choice of wording. But, it is open to the air....probably should be filtered...but that's a different story. In this case, glad it wasn't.

2) I drained the oil back out of the case. WOW It was about 2 gallons, no joke.

3) Let me run this by you- I'm probably out in left field on this, and the comment by MCRIDER about the pump check valve seems a likely suspect....but remember, I was doing all this oil checking and filling A) with the engine idling; and, B) with the cap to the oil reservoir REMOVED (so I could watch the oil level as I was filling). Now, is it possible that those things could have created the problem by themselves? Could the fact that the cap was removed while running the engine, created a no pressure situation that prevented enough pressure in the case to force oil to return to the side-tank AND create a low pressure reading (thus the dummy light)

I repeat, there is NO vent other than the valve cover breather tube that is open to the atmosphere. That spigot/vent/breather on the backside of the transmission is supposed to have a hose on it to the oil tank. That is a separate issue from the 2 main lines that plug in the side of the engine.

There is no "crank vent", that is open to the atmosphere. Period. Until you repair replace that hose, all diagnoses are suspect.

Other than that, your only other thing is the check valve in the oil pump.

OCICBW, but i don't think so.

At least we know the bulk of the oil stayted in the engine as i said it should.

BlackMax · « **Reply #14 on:** July 10, 2009, 05:50:31 PM »

Quote from: MCRider on July 10, 2009, 05:43:49 PM

Quote from: BlackMax on July 10, 2009, 05:06:15 PM
Okay folks.....here are the updates:

1) when I said "lower" crank vent....I simply meant the crank vent, as differentiated from the valve cover vent/breather. My bad choice of wording. But, it is open to the air....probably should be filtered...but that's a different story. In this case, glad it wasn't.

2) I drained the oil back out of the case. WOW It was about 2 gallons, no joke.

3) Let me run this by you- I'm probably out in left field on this, and the comment by MCRIDER about the pump check valve seems a likely suspect....but remember, I was doing all this oil checking and filling A) with the engine idling; and, B) with the cap to the oil reservoir REMOVED (so I could watch the oil level as I was filling). Now, is it possible that those things could have created the problem by themselves? Could the fact that the cap was removed while running the engine, created a no pressure situation that prevented enough pressure in the case to force oil to return to the side-tank AND create a low pressure reading (thus the dummy light)
I repeat, there is NO vent other than the valve cover breather tube that is open to the atmosphere. That spigot/vent/breather on the backside of the transmission is supposed to have a hose on it to the oil tank. That is a separate issue from the 2 main lines that plug in the side of the engine.

There is no "crank vent", that is open to the atmosphere. Period. Until you repair replace that hose, all diagnoses are suspect.

Other than that, your only other thing is the check valve in the oil pump.

OCICBW, but i don't think so.

At least we know the bulk of the oil stayted in the engine as i said it should.

Oh...... I see. That's not just a vent. Okay, I'll have to check the Klymer manual to see if I can figure WHERE that thing is supposed to connect. It's not like I can see any other vacant nipples.....but then, I haven't really checked hard. So, that could be the issue...plain and simple? By the way, I drained all the oil and re-filled with 3.5 qts. Sure enough, it again drained 100% out of the side-tank....bone dry.

Thanks for the help so far guys...just when I think I know it all....this type of things comes along and makes me feel dumb.

Kevin D · « **Reply #15 on:** July 10, 2009, 05:58:28 PM »

I'd be checking the return hose, the screen, the return pump.

http://data.sohc4.net/HSMCB750_1.pdf

Quote

I got my bike back, with rebuilt engine.

I'd be talking to my engine builder too.

Industrial Cafe · « **Reply #16 on:** July 10, 2009, 06:04:10 PM »

pull your oil lines off, check for a clog in the return line.
if that's not it, pull the pan and oil pump and blow the return hole out. turn the pump quickly by hand and it should push oil out (either way)

the inlet and return galleys are about an inch and a half long, and with the pump removed you can stick a zip strip thru and out the other side.

you should also be able to flow some starting fluid freely thru the 2 lines.

easy job, takes a 10mm socket for everything but the spigot collars.

if the oil pump is not burbling oil when you turn the gear then it's probably the valve.

the crank vent your talking about is right behind the bearing for the output shaft.
I used a vent tube from the auto parts store to replace mine.

MCRider · « **Reply #17 on:** July 10, 2009, 06:05:36 PM »

Quote from: BlackMax on July 10, 2009, 05:50:31 PM

Quote from: MCRider on July 10, 2009, 05:43:49 PM
Quote from: BlackMax on July 10, 2009, 05:06:15 PM
Okay folks.....here are the updates:

1) when I said "lower" crank vent....I simply meant the crank vent, as differentiated from the valve cover vent/breather. My bad choice of wording. But, it is open to the air....probably should be filtered...but that's a different story. In this case, glad it wasn't.

2) I drained the oil back out of the case. WOW It was about 2 gallons, no joke.

3) Let me run this by you- I'm probably out in left field on this, and the comment by MCRIDER about the pump check valve seems a likely suspect....but remember, I was doing all this oil checking and filling A) with the engine idling; and, B) with the cap to the oil reservoir REMOVED (so I could watch the oil level as I was filling). Now, is it possible that those things could have created the problem by themselves? Could the fact that the cap was removed while running the engine, created a no pressure situation that prevented enough pressure in the case to force oil to return to the side-tank AND create a low pressure reading (thus the dummy light)
I repeat, there is NO vent other than the valve cover breather tube that is open to the atmosphere. That spigot/vent/breather on the backside of the transmission is supposed to have a hose on it to the oil tank. That is a separate issue from the 2 main lines that plug in the side of the engine.

There is no "crank vent", that is open to the atmosphere. Period. Until you repair replace that hose, all diagnoses are suspect.

Other than that, your only other thing is the check valve in the oil pump.

OCICBW, but i don't think so.

At least we know the bulk of the oil stayted in the engine as i said it should.

Oh...... I see. That's not just a vent. Okay, I'll have to check the Klymer manual to see if I can figure WHERE that thing is supposed to connect. It's not like I can see any other vacant nipples.....but then, I haven't really checked hard. So, that could be the issue...plain and simple? By the way, I drained all the oil and re-filled with 3.5 qts. Sure enough, it again drained 100% out of the side-tank....bone dry.

Thanks for the help so far guys...just when I think I know it all....this type of things comes along and makes me feel dumb.

Sorry i should have given you a clue. Look on the backside of the oil tank up high. Is there a hose hanging downthat will reach to that breather nipple? If so plug it up and there is not much pressure there it should stay put. But i use a small hose clamp, Honda used one of those wire clamps like they use on fuel line. if you don't see the hose dangling look for a nipple on the backside of the oil tank same size as on the backside of the tranny. Get some hose from the hardware and do it up.

You would not be the first to have this problem onthe forum. And i did it to myself in 1972 when I replaced my first engine.

AS far as fixing the whole problem, possibly but not likely. A "wet sump" condition you describe is likely the oil pump chan valve, but first things first.

Did the mechanic open up the oil pump? Otherwise some debris may be lodged in the chackvalve.

Industrial Cafe has some good ideas too.

Industrial Cafe · « **Reply #18 on:** July 10, 2009, 06:13:32 PM »

bet its some packing peanuts jammed up in there

(don't ask)

BlackMax · « **Reply #19 on:** July 10, 2009, 06:21:41 PM »

ok, got a hose on the nipple at the rear of the trans. to the bottom of the tank. I have 3.5 qts oil in there.....ran it a bit, RED light came back on at all RPMs below about 2500. Also, oil tank is empty again.

So, there is a problem getting oil back to the tank, due to whatever cause. The mechanic didn't do anything to the bottom of the motor. So, I can't imagine he ever saw the pump. However, he did have to remove the lines. Surely there can't be anything in there.... This is becoming really fun $:-\$
Oh, and one other thing......how about this- Hey Honda, how about just puting the freakin' oil in the crank case like all other bikes on earth, before and after......geez.

Industrial Cafe · « **Reply #20 on:** July 10, 2009, 06:24:19 PM »

hahahaa....
I'm sorry man, I mean no disrespect but I'm honestly laughing out loud.

there's no pressure situation in the tank, you will be able to watch the oil swirl around with the cap off. that breather is just to circulate oil vapor back into the oil tank.

follow this.

Quote from: Industrial Cafe on July 10, 2009, 06:04:10 PM

pull your oil lines off, check for a clog in the return line.
if that's not it, pull the pan and oil pump and blow the return hole out. turn the pump quickly by hand and it should push oil out (either way)

the inlet and return galleys are about an inch and a half long, and with the pump removed you can stick a zip strip thru and out the other side.

you should also be able to flow some starting fluid freely thru the 2 lines.

easy job, takes a 10mm socket for everything but the spigot collars.

if the oil pump is not burbling oil when you turn the gear then it's probably the valve.

the crank vent your talking about is right behind the bearing for the output shaft.
I used a vent tube from the auto parts store to replace mine.

Industrial Cafe · « **Reply #21 on:** July 10, 2009, 06:30:35 PM »

I'm not really laughing at you, I'm laughing at the fact that no one flat out said that (including myself) up until now.

Quote from: Industrial Cafe on July 10, 2009, 06:24:19 PM

there's no pressure situation in the tank, you will be able to watch the oil swirl around with the cap off. that breather is just to circulate oil vapor back into the oil tank.

BlackMax · « **Reply #22 on:** July 10, 2009, 06:33:32 PM »

I'm not really laughing at you, I'm laughing at the fact that no one flat out said that (including myself) up until now.

yea, I couldn't figure how that could cause a problem.....it's not like there would be vacuum at that port, so I didn't really get it....but was hoping that was the magical fix.

But then again, why the FLIP did Honda get so tricky and add a damn external oil tank!!??

I mean, pouring oil in the crank case like everybody was a problem? Man, this is killing me (and messing up my carpeted garage!)

Industrial Cafe · « **Reply #23 on:** July 10, 2009, 06:35:27 PM »

hey looking at the bike, front line on the motor goes to the outside port on the tank, and back line inside port on the tank, correct?

Industrial Cafe · « **Reply #24 on:** July 10, 2009, 06:36:27 PM »

i don't remember, year/model?

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Author Topic: What the???? Amazing vanishing oil trick.....sort of (Read 4022 times)