hi all

i have just finished fitting an oil pressure gauge to my k100rs ,the gauge is from an old R bike (vdo), bought on ebay, and the sender unit is a vdo-type ,that means its a cheap china product , the gauge is a 0-10 bar , and the sender is 10-180 ohms , wich should be right. 

well now, here is the question, when using a5/40 oil , the best reading i could get was 4bar at speed , and the warning lamp flashing at idle ,the contact in the new sender breaks at 11 psi, wich is higher than the standart , 

i then changed oil to a 10/50 , this didnt change the oil pressure at speed, but did raise the pressure at idle to about 1,5-2 bar.
i have read that the oil pressure should be 5-6 bar , so 4 bar is on the low side ,however the engine runs great , no unwanted sounds , oil consumtion is low , around 1l/8000km  .

i can see two possebileties : maybe the gauge and sender unit doesnt fit together after all  :|,
or could it be the pressure relief valve in the oil pump being faulty?

looking forward to hearing from you gents.

best regards


k-rider

Well i Will try again, does anyone know if 4bar is what to expect from A 25year old engine ,or should i be worried and start looking for worn out big end bearings ,and other fun stuff  

K-rider

4 bar = 56psi. For an older engine that sounds about right to me and if you're not burning excessive amounts of oil then there's nothing to worry about.

Thanks Dai 

This is what i was hoping,since it runs so well😀,
By the way good work on your own bike, New wiring and All,not bad,😉

K-rider

interesting observation about the oil pressure relief valve

I would be thinking it would be fair to assume that the spring in the valve could be somewhat lower pressure than a new one

would be good to see the difference that a replacement made

many have replaced the seals but possibly none have done the spring ?

I don't consider that 4 bar would be too low for a slipper bearing engine. With many engines anything above 5 bar will scour the metal from the bearing shells.

charlie99 wrote:interesting observation about the oil pressure relief valve

I would be thinking it would be fair to assume that the spring in the valve could be somewhat lower pressure than a new one

would be good to see the difference that a replacement made

many have replaced the seals but possibly none have done the spring ?

The reason i thought about the pressure relief,was that the pressure would only rise at idle and low rpm,above 2700,it stats at 4bar, regardless the rpm,One would think that the pressure should be A bit higher ,Even if the engine was not New.
This indicates that either the is not capable of higher pressure ,or the relief valve could be faulty .

RicK G wrote:I don't consider that 4 bar would be too low for a slipper bearing engine. With many engines anything above 5 bar will scour the metal from the bearing shells.

Glad to hear that you think 4bar should be sufficient, and i am amazed to hear that a 5 bar pressure could ruin the bearings   ,i believe that it should be safe on our engines, since the oil pump is designed to deliver 5-6 bar? 

K-rider

What a pump is designed to deliver and what actually does deliver are often two different things. Not because it's faulty, but because it's under-driven compared to what it's able to deliver at full chat.

k-rider wrote:

RicK G wrote:I don't consider that 4 bar would be too low for a slipper bearing engine. With many engines anything above 5 bar will scour the metal from the bearing shells.

Glad to hear that you think 4bar should be sufficient, and i am amazed to hear that a 5 bar pressure could ruin the bearings   ,i believe that it should be safe on our engines, since the oil pump is designed to deliver 5-6 bar? 

K-rider

I would say that if the pump does deliver 5 or 6 bar then the slippers would be capable of handling that but bearings that usually only run 3 bar then get 5 bar will scour very quickly.
I had a friend who had a circuit racing car with a mid engine V8 and it kept running and spinning bearing shells and it took a bit of talking to convince him that too much oil pressure was the problem but eventually he dropped the pressure back to what the engine ran in standard trim and it ran a whole season with any disasters.

Thank you very much for your replys, im No longer worried about the oil pressure, but still A bit puzzled, that from 3000-8500. Rpm,the pressure don't change  ,when i get A spare moment i Will investigate further. 


K-rider

k-rider wrote:Thank you very much for your replys, im No longer worried about the oil pressure, but still A bit puzzled, that from 3000-8500. Rpm,the pressure don't change  ,when i get A spare moment i Will investigate further. 


K-rider

That's because the pressure relief valve wont let the pressure go any higher, no matter what revs you take it to.

Avenger GT wrote:

k-rider wrote:Thank you very much for your replys, im No longer worried about the oil pressure, but still A bit puzzled, that from 3000-8500. Rpm,the pressure don't change  ,when i get A spare moment i Will investigate further. 


K-rider

That's because the pressure relief valve wont let the pressure go any higher, no matter what revs you take it to.

my thougts exactly, except the pressure relief valve should not open before 5-6 bar ,
at least according to ;TEKNICK IM DETAIL; on the flying brick forum, maybe charlie is right about the spring being to soft after 25 years:bounce: .