hi, I am swapping my ZX9r for a ZX12r, got the engine fitted, all cooling/fuel and electrics sorted. I have cranked the engine - plugs out/fuel pump disconnected, hoping to see the oil pressure light go out - but it dosnt. A friend points out that the oil pump wont be doing a lot at cranking speeds, and I know a lot of bike engines sometimes show the oil light when at hot tickover. BUT I took the oil pressure sender out, and briefly cranked - I expected to see some oil coming out of the hole, but nothing did. the sump was plenty full.
I am tempted to start it to see what happens ( once I have an exhaust manifold) but don't want to rev it much until the oil light goes out.
Or am I just worrying too much ??
Any thoughts !

No I don't think the pressure will be enough just cranking it over. Running it for a few seconds would be fine to check the light goes out.

I'd highly recommend fitting an oil pressure gauge, they're a great indication of potential problems!

On my cbr900, oil pressure takes a couple of seconds from starting the engine to register on the gauge, then when cold goes up to around 20psi at idle, coming down as it warms.
Hot pressures, I get around 5-10psi at idle and 70-75psi at 6k rpm

I find the oil light totally useless. I once lost my sump plug and only had the oil light come on after the engine had totally siezed up!

I don't know much about bike engines, but the car engines I've played with like to be started and run to get the oil pressure right. I suspect cranking speed isn't enough to do it for you.

It may be that the engine has been standing a long time the oil has totally drained down and needs a good run to prime the system up again?

I found this out on mine the first time I cranked it, these engines need 'burping' to get the oil up the galleries and into the oil filter. DO NOT RUN the engine like this or you will ruin it. Its messy but best to loosen the oil filter just enough to open the seal and crank it over without the injectors plugged in and wait for the oil to spray out of the filter seal, then redo back up and crank again and this should then give pressure for the light to go out.

I have to do this every oil change too, not a huge issue if you don't mind wiping down the chassis under the filter afterwards.

Thanks for the replies, I was thinking of getting a pressure gauge and a 20psi switch for the light.
The engine will have no oil in it, I have had the filter/oil cooler off, also the little transfer pipes in the sump off, I was thinking of slightly pressurising the crankcase - airline via the breather, that should in theory push the oil into the galleries, or at least help the pump pick up.
I had a Nova stage rally car a few years ago, I know how quickly an engine can self destruct when starved of oil, at speed, under load, probably makes me a bit over cautious where oil pressure is concerned !

20psi switch for the light is no good really.

My pressure is down below 10psi at idle

I think just doing what I have suggested will sort it, 5 second bursts on the starter to not over heat it and it will get pressure.

When I modified my sump I also removed those pipes in there, but it soon re pressurised.

I also agree, 20 psi is too high, my pressure gauge reads just over 0 when hot and at idle but the light stays off with the standard zx12 switch.

Good luck.

I just did an oil change in my zx12r car. Despite cranking (fuel pump disconnected) in bursts for around a minute, the light did not go out. I figured it was well primed by then. I reconnected the fuel pump and it fired straight away and within a second or two the light went out and thr pressure built-up. Scary as i have an accusump and it is a lot to prime at such low revs/pressure, but it seems to be the norm.

Just an update on this one, I spent some time looking thro ZX12r forums, and getting the oil pump to prime is a problem on these, when they have been rebuilt or have no oil in them. A thread on ZX12rzone.com recommended pressurizing the crankcase via the breather pipe, I did this - ignition on, applied about 15psi, oil light went out ( engine not turning) I was then happy to start the engine. It might be on the road soon !!

This is probably a good thing to do on any freshly built engine, suspect it cant do them any good to be cranking without oil in the pump/galleries/bearings. I know of some industrial diesel engines that have a hand pump to prime the oil system prior to starting.