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Old 06-02-2015, 06:03 AM   #1
mpan OP
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Oil pressure reassembled r75/6 engine

Hello,

I have a BMW r75/6 from 94'. This winter I've had the engine apart to change all gaskets, piston rings etc.

To the problem. Starting up the bike for the first time went smooth but it took the oil lamp 5-7 seconds for it to go off. I didn't prime it a lot. Basically just poured in some oil when i put the oilpump back in.

When I started it up again just 2 minutes after, the oil lamp wouldn't turn off. Checked oil level and it is at max. And then tried once again and the oil lamp would go off immediately. Thought it was weird but I figured it was just the first start for the oil pump to push oil through out the engine.

I have new carbs so I started tuning them but I got problems with my oil pressure lamp again so I stopped since I was afraid of doing damages. Worth mentioning is that the lamp never flickered or went off when i had more throttle. Just either on or off randomly. Went and bought an oil pressure gauge. I got 5 bars with in just a few moments and it looked fine. Tried turning the bike off and on again with different intervals and got the same result.

This is where I fucked up. I just assumed the oil sensor or electrics were fucked after my renovation so I disconnected the cable and ordered a new sensor. And got back to tuning my carbs. I've had the bike running for 10 minutes in total and i thought i would just check the oilpressure once more. And now I get 0 bars. I even removed the oil sensor and started the bike and nothing comes out... FUCK... WTF?

So I open up the bottom end. Everything looks fine. Removed the gearbox and have a look at the oilpump which looks nice, not a whole lot of oil coming out but still a bit. No more marks or anything than from when I had it apart. The clip onto the cam is there and i've reassembled it correctly. Tried blowing air from the pump area out to the sensor area with full success.

So here we are pretty much. I have no idea whats going on. Sometimes I have 5 bars in oilpressure and sometimes 0.

I've read a couple of threads here on the forum and It's mostly about how people didn't prime it. I know Im in that boat. But I also wanted to create a new thread since I don't know how much damage I might have caused and If I should take everything apart again. Would be sad, since I had hoped to have a bike to run this summer.

What is my next action?

Thank you,
Marc
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Old 06-02-2015, 06:47 AM   #2
Bill Harris
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Very strange. Priming or mechanical problems with the oil pump probably are not the cause. Most likely could have been the oil pressure switch and it's wiring, but you've checked that. The frustrating thing is the intermittent nature of the low pressure.

You have a post-1977 so it has the new o-ring oil filter system and this is suspect. Here is a great information article on oil filter systems:

http://largiader.com/tech/filters/

The only other thing I can think of is the oil pickup screen in the oil pan-- if the bolts are loose, it will sometimes suck air instead of oil and cause a low pressure condition.

Good luck...

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Old 06-02-2015, 06:56 AM   #3
PaulRS
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No need to prime.

I always use plenty of oil during assembly when building an engine, pour in 2 liters of oil, remove valvecovers and sparkplugs and hit the starterbutton.
If all is well, after a few sec the oilpress light goes out and a few sec later oil appears at the rockers.
Priming done.

As mentioned by Bill, check the filter for correct assembly, same for the oil pick-up.

Another thing to check, if all others check out ok, is the overpress relief valve, on top of the front crankbearing housing.
That's just a ball and spring in a tube, not known to fail, but then, stranger things has happened.

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Old 06-02-2015, 07:30 AM   #4
mpan OP
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Thanks!

I have double and tripple checked the pressure release valve in the oil filter canister. I use short filter with just the gasket for my flat cover. The filter have rubber sleeves at both ends. Looks like about right from the link Bill sent me.

Will check the bottom-end again.

What about engine damage after it's been on a couple of minutes with probably bad / no pressure sometimes? :/
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Old 06-02-2015, 07:59 AM   #5
PaulRS
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So you have the flat cover, this means the filter is held in place by a round cover with a central bolt, correct?

As for the damage, without oilpress, things can go wrong in a minute.
I'd pull the conrods and check the bearings, that gives an indication.

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Old 06-02-2015, 08:07 AM   #6
mpan OP
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Originally Posted by PaulRS View Post
So you have the flat cover, this means the filter is held in place by a round cover with a central bolt, correct?
Yes
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Old 06-02-2015, 08:15 AM   #7
Bill Harris
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Post-1978, that should not be. Lets see some photos of you oil filter set-up.

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Old 06-02-2015, 09:46 AM   #8
PaulRS
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Originally Posted by mpan View Post
Hello,

I have a BMW r75/6 from 94'.

Marc
Me thinks 94' should be '74.

Then the oilfilter config is correct, same config as my '76 /6.

So no 2000€ white O-ring and steel back-up ring as used on later models.

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PaulRS screwed with this post 06-02-2015 at 09:59 AM Reason: Typo
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Old 06-02-2015, 11:31 AM   #9
Bill Harris
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Methinks you are correct. I saw '94 and thought 2000 o-ring, too.

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Old 06-02-2015, 06:28 PM   #10
bmwrench
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Once in a while, someone puts an excessively long in the oil pan which keeps the round cover from sealing the canister.
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Old 06-02-2015, 08:02 PM   #11
CafeDude
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Originally Posted by bmwrench View Post
Once in a while, someone puts an excessively long in the oil pan which keeps the round cover from sealing the canister.
Bolt?
Magnet?
Dipstick?
Spacer?
Sponge?
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Old 06-03-2015, 12:49 AM   #12
mpan OP
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Quote:
Originally Posted by PaulRS View Post
Me thinks 94' should be '74.
Yes, sorry about confusion. It's an early 1974 r75/6
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Old 06-03-2015, 10:28 AM   #13
disston
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Is there a lot of oil spilled under the trans now on the shelf under the trans? If not then the oil pump is working at least enough to provide minimum oil flow. You did put two pieces in the oil pump, an inner and outer pump parts and the correct O-ring under the oil pump cover?

If this was done correctly then I'm afraid you have to next take the timing cover off the timing chain so the oil pressure relief valve can be checked. The relief valve is part of the front bearing carrier that is under the timing chain. It has a spring that sometimes, rarely but it can, break.



The horizontal tube above the chain.
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Old 06-03-2015, 06:39 PM   #14
bmwrench
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Originally Posted by CafeDude View Post
Bolt?
Magnet?
Dipstick?
Spacer?
Sponge?
Bolt. I'm sorry.
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Old 06-04-2015, 12:23 AM   #15
ME 109
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No oil coming out of the sender unit hole............not much point looking at the pressure relief valve. Oil would still come out the sender hole regardless of the pressure relief valve. Which btw can't fall out on my /7 engine, don't know about other models.
So no oil at the sender says the pump is not picking up oil, or the oil filter system is blocked. But I reckon the oil pump would blow any blockage.

mpan, did you install the shim onto the end of the cannister? Hopefully not between the cover and o-ring.

Even with a stuffed o ring I'd expect at least some oil at the sender hole?
Did you put the woodruff key back in the oil pump?

Odd that oil pressure is coming and going, by the gauge.
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