Proper Oil pressure for Dnepr MT9?

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Korto
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Proper Oil pressure for Dnepr MT9?

Post by Korto » Thu Dec 13, 2018 7:25 am

Does anyone know what the oil pressure should be for a Dnepr MT9? And at different engine speeds?

I was about to take my restoration to the engineer's for approval, and found my oil-light lighting up when accelerating and at road-speeds, but no problem at idle / low revs.
I'm buying a gauge to check the pressure, but I don't know what the pressure should be. I can't help but feel this will make it more difficult.

(Took a frigging month and a half to get that bloody appointment, too. Then I had to call and cancel it...)
Australia, Newcastle. 1972 Dnepr MT-9... mostly... I think...

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Re: Proper Oil pressure for Dnepr MT9?

Post by propwash » Thu Dec 13, 2018 12:18 pm

Generally, an OHV Dnepr will produce around 50-60 psi at idle. A little more off idle.
Usually when people have issues with oil pressure, the light comes on at idle and goes off with some RPMs.
Might want to remove oil pan and inspect the oil pickup.
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Re: Proper Oil pressure for Dnepr MT9?

Post by Korto » Sat Dec 15, 2018 4:14 am

Well, got the gauge and had a measure. That was interesting.

First, a little background. The reason for this will become apparent later.
(Flashback)
The PO (previous owner, I believe?) at some point tried to convert it to 12V, but quit part way through. I reverted it back, by getting some parts and handing it off to an auto-electrician to do the wiring. They never, however, replaced the 12V bulbs in the instruments. I only a few weeks ago managed to source some suitable 6V and put them in. A brief test to make sure they worked, and then left the bike as I was trying to get the engineer's appointment.

(Back to now)
Testing the pressure, and I get a reading of 46 psi idling, up to 64 psi revving it up. I also notice the oil light is still glowing,which strikes me as very odd since I removed the switch to attach the gauge, and the lead isn't attached to anything.
I touch the lead to the body, and my "Battery Charging" light comes on.
It turns out that my oil light was wired into the "Battery Charging" wire, and the "Battery Charging" wire was wired onto the oil switch. I'd never noticed this, because both light up at switch-on, and then both go out at idle--one because there's now oil there, and the other because there's not actually enough electricity being generated to charge the battery at idle. BUT go fast enough, and there IS enough power being generated...and so my oil light dutifully comes on.
I'd never noticed before because with the 12V bulbs, they were too dim to see without paying explicit attention, anyway.
Australia, Newcastle. 1972 Dnepr MT-9... mostly... I think...

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Re: Proper Oil pressure for Dnepr MT9?

Post by propwash » Sat Dec 15, 2018 10:51 am

Your oil pressure is good - that's good.
So all back to normal?
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Re: Proper Oil pressure for Dnepr MT9?

Post by 3 bike mike » Mon Dec 17, 2018 5:38 am

Is your oil pressure lower when the engine is hot ? i also have mt9 and use 20/40 oil. I get around 40psi with revs and hot oil. but 55 psi with revs and cold oil !!

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Re: Proper Oil pressure for Dnepr MT9?

Post by Claus » Mon Dec 17, 2018 7:51 am

According to the workshop manual the oil pressure should be 55 to 87 psi @ 1000..1200 rpm and minimum 43 psi @ 500 rpm. Above 87 psi the bypass valve should open.
I have learnt over the years that at idle the pressure should be above 30 psi with hot oil 20W50 or HD50 and should go around 50 to 65 psi when riding.

The oil pressure switch opens @ between 25 and 33 psi (that´s when your light comes on), the bypass valve opens (according to the manual) between 55 and 87 psi..

So everything between 43 and 87 psi should be normal and o.k . This is a wide range but the tolerances are enormous and wear does play a role, too.
And there was a lot of wishful thinking by the manufacturer when he created the technical data table :-)
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Re: Proper Oil pressure for Dnepr MT9?

Post by Korto » Thu Feb 14, 2019 6:27 am

Sorry for not getting back sooner. You know, Christmas, hospital visit for surprise abdominal surgery, the usual.
And thank you for the oil pressure information.

Managed to get another engineer's appointment, at which point he told me that he also wanted the seat moved back 40mm, and one of the rear brake connections moved up 8mm. I think I hate engineers. Of all the petty bullshit...

Now the welder's finished those jobs, and I started the bike up to tune the carbs today, the damn thing's started dripping oil from both cylinders, and solid trickles from the front and back of the bloody generator.
I think I hate that bike, too.
Australia, Newcastle. 1972 Dnepr MT-9... mostly... I think...

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