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Author Topic: Idle oil pressure  (Read 316 times)

tomo3

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Idle oil pressure
« on: August 27, 2018, 12:33:00 pm »
Hello, once or twice a year I start my Nuovo Falcone, usually with no problems. This year, right after the start, oil warning light came on. To be sure what's going on, I changed oil (I put Mobile 20-50), and warning light went off, except on idle when engine is hot. Since engine idle is adjusted very low (as most of Falcones cca. 450 rpm), I bought a new oil indicator (it fits from Fiat 127 903 ccm engine). The same thing happened and on idle with hot engine the oil light is on. As soon as I rev the engine a little bit, it goes off. Does anybody knows what's oil pressure on idle in bars and what is oil pressure needed to turn off the oil warning light (I can not find any datas). I wouldn't like to have to much of expenses since the bike stands in the garage for five years and in the future it probably will be the same. Is it possible to repair the oil pump, or shall I simply raise the idle speed and solve the problem with oil light?

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banquo

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Re: Idle oil pressure
« Reply #1 on: August 27, 2018, 04:17:51 pm »
I'd be worried about that Tomo. Raising the idle speed is not fixing the problem; just disguising it by increasing the pump speed. If the oil pressure is low at idle, and the sender unit has the correct pressure for the NF (how do you know if it does?) then you will have low pressure at all engine speeds. The camshaft is only lubricated on the NF after the pressure relief valve opens, so it's possible that if you have low oil pressure the camshaft will never get lubricated. Possibly the problem is the oil pump, but the other possibility is wear on the bush that supports the crankshaft in the timing case. This bush is required to maintain oil pressure, but it's a really bad design, and when worn, allows the oil to leak past. Some people have fitted an o-ring or a proper oil seal in there, as the bush isn't required for support, only to seal, and allow oil to be delivered to the big-end bearing. I'm sorry, but I don't have the pressure at idle, but I think the pressure relief opens at 60 psi. Id I were you, I'd try an oil pressure gauge, so you can see exactly what is happening. If the pressure really is low, you risk some very expensive engine damage.

tomo3

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Re: Idle oil pressure
« Reply #2 on: August 27, 2018, 04:52:58 pm »
Banquo, thanks for the quick reply. I'm also worried since this happened for the first time. I tried to run it in idle without oil indicator (unscrewed) and very quickly engine was covered with oil leaking from the indicator hole (so it seem to have decent pressure in idle). I'll check the oil pressure with diagnostic tool and decide what to do next. Even thou the bike is not in everyday use, I'd like it to be completely functional.  If I'll have additional questions, I'll be free to ask.

banquo

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Re: Idle oil pressure
« Reply #3 on: August 27, 2018, 09:19:41 pm »
There's a big difference between flow and pressure. If the pump's working, and you open the oil cavity by removing the sender unit, then oil will flow, because you created an easy path for it, but the lubrication system does require high pressure oil to feed the big end bearing and the camshaft. I'm no expert on this, but I do know the crankshaft bush is a definite weak point. It may be worth your while to remove the clutch cover and inspect it. Instruction in the Paul Friday files that you can download via the links section.

cloggy

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Re: Idle oil pressure
« Reply #4 on: August 28, 2018, 06:16:58 pm »
I would run the  idle at the same speed as a brit single so that the bypass valve opens up and feeds the cambox. Running it low is a party trick

banquo

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Re: Idle oil pressure
« Reply #5 on: August 28, 2018, 06:37:15 pm »
Relief valve isn't even thinking about opening at tickover Cloggy. It opens at something like 60psi and pressure at idle is more like 25 psi. I don't think the valve opens until about 3000 rpm. They say you're better thrashing the engine than molly-coddling it for best engine life, and especially camshaft life