Author Topic: Oil flow to engine  (Read 2856 times)

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Offline cuz

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Oil flow to engine
« on: February 07, 2016, 07:23:04 pm »
I have added oil to the oil tank for the first time since the rebuild on my cb750k7.   For some reason it doesn't want to flow in to the engine case.   I can take the oil lines off and its flowing there.   I cranked the motor on the starter a few times then checked the oil pan drain and the oil filter to find no oil.   The oil tank is still filled right up with about 2 liters in it.   It's only about 17 degrees Celsius in my garage but that should be warm enough to flow oil.   Any thoughts?

Offline Elan

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Re: Oil flow to engine
« Reply #1 on: February 07, 2016, 08:30:48 pm »
Gotta prime that oil pump
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Offline Don R

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Re: Oil flow to engine
« Reply #2 on: February 07, 2016, 08:38:47 pm »
 I like to pour some oil into the oil galley through the plug on the right side (funnel and hose) and also dump some into the rocker cover holes.
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Offline cuz

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Re: Oil flow to engine
« Reply #3 on: February 07, 2016, 08:43:05 pm »
I primed the pump but I'll give it a try again.   I thought more would free flow in to the oil pan for the pump to pick it up.

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Oil flow to engine
« Reply #4 on: February 07, 2016, 08:47:51 pm »
Gotta have suction to move it from the tank to the pump. Pour 1.5 quarts into the valve cover to get it to the pan.
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Offline mystic_1

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Re: Oil flow to engine
« Reply #5 on: February 08, 2016, 03:50:14 am »
I primed the pump but I'll give it a try again.   I thought more would free flow in to the oil pan for the pump to pick it up.

The pump doesn't draw from the oil pan, or at least not in the way you seem to think.

The pump draws directly from the hose coming from the tank, and then sends the oil to the oil filter.  Once it has circulated throughout the engine, THEN it ends up in the pan where it is picked up by the return side of the pump and returned to the tank.

How long did you spin the starter? 

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Offline cuz

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Re: Oil flow to engine
« Reply #6 on: February 08, 2016, 05:34:55 am »
Thanks Mystic.   I ran it about 5-6 bursts that lasted about 20 seconds long or so.   I'll prime the pump again and give it another try tonight.   

Offline mystic_1

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Re: Oil flow to engine
« Reply #7 on: February 08, 2016, 05:53:30 am »
Hmm, that does sound like long enough to get things moving.

You can remove the oil filter and then spin the engine over while watching the lower port at the oil filter mounting area to see if you get oil coming out of there.


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Offline 70CB750

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Re: Oil flow to engine
« Reply #8 on: February 08, 2016, 05:55:19 am »
After every oil change I prime the engine with Kill Switch Off watching the oil pressure gauge.  It takes 40 - 50 seconds for the oil pressure to build up - and the oil pump is full.

Offline mystic_1

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Re: Oil flow to engine
« Reply #9 on: February 08, 2016, 05:59:39 am »
BTW, after a full rebuild, you won't find oil in the pan until it's been pumped all the way up to the top of the engine and trickles back down, or until the crank bearings trickle through enough oil to run back into the pan.  The transmission is lubed off of the return side of the pump, which does nothing until the pan is filled, and so the whole back half of the engine is dry until then.

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Offline flybox1

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Re: Oil flow to engine
« Reply #10 on: February 08, 2016, 06:43:40 am »
You need to pour at least 1 qt up top into the tappet holes.  This does two things.
it'l lkeep the top end lubed until the system primes, and it'll allow the system to prime faster as you're not waiting for the oil pump to fill the whole system.
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Offline cuz

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Re: Oil flow to engine
« Reply #11 on: February 08, 2016, 06:31:51 pm »
Well I'm at a loss here.   I took the pump out and filled it with oil while rotating it a bit to get any air out.   I also poured about a litre of oil in to the top end via the tappet covers.   After cranking it again still no flow of oil out of the tank.   The return side of the pump did manage to return somesome of the oil that I drained in to the top end back to the tank.   I don't want to continue cranking the engine as I'm worried I'm going to damage something running it dry of oil so much.  HELP

Offline mystic_1

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Re: Oil flow to engine
« Reply #12 on: February 08, 2016, 06:34:21 pm »
Did you crank it with the oil filter off?

The oil filter is the first place that oil goes after the pump, so checking there should be pretty definitive.

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Offline cuz

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Re: Oil flow to engine
« Reply #13 on: February 08, 2016, 06:37:05 pm »
Yes,  I tried that.   Nothing coming out there.   I did put new o-rings in the pump and checked the tolerances.   I was certain they spec'd out fine.   

Offline cuz

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Re: Oil flow to engine
« Reply #14 on: February 08, 2016, 07:37:09 pm »
I'm wondering if it could be one of the valves in the pump.  I did have the whole thing apart and put new o-rings in.  It's possible that I put something in backwards and its not letting the oil past and towards the oil filter.  Please forgive me if that is not the function of the valves that are in there. 

The pump did return some of the oil in the tank that I dumped in the top end of the motor as the level in the tank increased as I turned the engine over. 

Offline mystic_1

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Re: Oil flow to engine
« Reply #15 on: February 08, 2016, 08:02:43 pm »
That's not impossible.

There are two valves there, detailed in the lower right corner of the diagram above, and here:



The valve (#10) under the cap that is secured with two hex bolts (#13) is the "leak stopper valve" this prevents oil from running through the pump under the force of gravity, when the bike is not running.  It should pop open under light pressure once the bike starts running, I don't know if there's a spec on this but someone else here may know (elan?).  This valve has a piston (#10) with a rubber face (#11), held closed by a spring (#12).



The other valve (#5) is under the round cap (#7) with the hex shape cast into it.  This is an all-metal plunger (#5) with a stiffer spring (#6) than the other valve, this is the pressure relief valve, it opens when the oil pressure gets too high and relieves pressure by dumping into the sump.



It's possible that your leak stopper valve is stuck closed, or your pressure relief valve is stuck open.

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Offline cuz

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Re: Oil flow to engine
« Reply #16 on: February 08, 2016, 09:08:38 pm »
Thank you very much for the information Mystic.  I'm going to pull the pump again tomorrow and have a closer look at how I reassembled everything.  Just hope I didn't burn anything up in the motor running it on the starter. 

Offline turkey4me

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Re: Oil flow to engine
« Reply #17 on: February 09, 2016, 05:47:24 am »
I could loan you my spare oil pump if it would help you troubleshoot your project.  It's from a 78 750F

Offline cuz

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Re: Oil flow to engine
« Reply #18 on: February 09, 2016, 06:49:31 am »
Thanks turkey4me.  I'm going to give my pump one more try tonight.  If nothing changes I might take you up on that. 

Offline flybox1

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Re: Oil flow to engine
« Reply #19 on: February 09, 2016, 07:13:49 am »
after i rebuilt my F3 engine, i got the same.  no flow and oil light still on.
only after encouragement from the forum to start it, i did, and within seconds, the oil light went out and oil was flowing.
I dont think kicking it or using the starter can build pressure and sustain it enough for a visual of it at the tank.
Just start it. As long as you have oiled the top end, you'll have a good 10 seconds to decide if you need to shut it down.
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Offline keith89

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Re: Oil flow to engine
« Reply #20 on: February 12, 2016, 10:38:37 am »
I had the same issue last week with a new round oil tank, oil cooler, and -AN lines.  The engine was dry and I had rebuilt the oil pump.  Of course I forgot to prime it before putting it in the engine.  To top it off, I put a cyclexchange charging system on, so no more starter.
I figured I'd put some oil in the engine through the tappet covers just to get some lube in there.  After cranking it over witht he kickstarter for a few minutes, I had nothing flowing through.  Oil was making it fromt he oil tank down the hose and to the pump, but the pump was airlocked.

I got oil flow/pressure by blowing into the breather tube while turning the engine with the kickstarter.  Within 10 kicks, pressure started to build and the oil level in the tank dropped as it filled the oil filter and oil passages.

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Oil flow to engine
« Reply #21 on: February 12, 2016, 12:17:01 pm »
Just fired mine up and the pump works. Poured almost 2 qts in from above to get it to the sump. Should be enough to cover the screen and prevent it from sucking air. I did 3 or 4 bursts 10+ seconds maybe with just the starter. Nothing. Same as the last one, I 'primed' the pump first and most ran out anyway. I worried way too much on that one without merit. Soooo....Gassed it up, let the bowls fill, gave it some choke and hit the starter. Started almost instanteously Pressure within 5 seconds.
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Offline mrbreeze

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Re: Oil flow to engine
« Reply #22 on: February 12, 2016, 12:43:30 pm »
That's not impossible.

There are two valves there, detailed in the lower right corner of the diagram above, and here:



The valve (#10) under the cap that is secured with two hex bolts (#13) is the "leak stopper valve" this prevents oil from running through the pump under the force of gravity, when the bike is not running.  It should pop open under light pressure once the bike starts running, I don't know if there's a spec on this but someone else here may know (elan?).  This valve has a piston (#10) with a rubber face (#11), held closed by a spring (#12).



The other valve (#5) is under the round cap (#7) with the hex shape cast into it.  This is an all-metal plunger (#5) with a stiffer spring (#6) than the other valve, this is the pressure relief valve, it opens when the oil pressure gets too high and relieves pressure by dumping into the sump.



It's possible that your leak stopper valve is stuck closed, or your pressure relief valve is stuck open.

mystic_1
I'm not saying that this is the problem but I wanted to point something out here. I just pulled my pump out the other day to install Elan's stopper seal kit and found a problem with the exploded view of the pump. In this picture which is in the shop manual and the Chiltons the valve (piston) which is #10 in the drawing looks to be all the same diameter. It is in fact a smaller diameter on one side. The smaller diameter goes into the bore first. This is the side where the seal sets. The larger diameter is on the outside where the spring sets. I don't know what happens if this is installed backwards but I thought it could be a problem.
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Offline rickibrown

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Re: Oil flow to tank
« Reply #23 on: December 27, 2020, 10:59:51 am »
I rode my new to me 1978 cb750 220 miles and replaced oil hoses due to leaks.
Since then no return oil to tank Assuming and air pocket solutions please.
I have new pump kit but nothing wrong until I replaced hoses.

Offline robvangulik

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Re: Oil flow to engine
« Reply #24 on: December 27, 2020, 01:58:06 pm »
New or used hoses? Did you check they were 'freeflowing'? How did you conclude to the no return issue?