SOHC.co.uk Forums > CB750
Oil pressure issue / motor rebuild
Nurse Julie:
Looking lovely, well done.
MrDavo:
I'm confused. How much turning over is necessary to fill the oil filter up from empty?
I fitted the oil tank & hoses, and put some oil in the tank. Many kicks later and a couple of spins of the starter, no oil had made it up as far as the gallery, never mind the oil light going out. I dropped the sump and the oil I'd just put in, and reprimed the oil pump. All appears fine with the pump, I don't really see how I could put it together wrong - (unless you know different- Trigger?).
Refitted, refilled, still nothing.
Maybe I'm being impatient, it's a big filter housing and tiny chambers on the feed side of the pump, but I'm paranoid about turning a dry motor over too much. Will I only get pressure when I start her up?
ETA: I found a similar thread on dot net, it turned out OK in the end. http://forums.sohc4.net/index.php/topic,101556.0.html
Trigger:
These are a bugger to get all the air out of the system. I find filling the pump with Vaseline works as a very good prime. I would not try to push the button just yet, keep kicking it. When you built the engine back up, I hope you used Graphogen or the equivalent.
Another good trick is to take the oil pressure switch out and with a little funnel, fill it with oil.
K2-K6:
Even when you work on them normally in servicing them after the filter is changed and you've filled the oil tank with new oil, then you can see the tank level drop by something like the volume of the filter and that's without any of the engine galleries being empty.
It's a big worry with any engine if it doesn't appear to be building pressure, and always a bit of a nail biter as to whether to continue turning over or investigate.
All things being in place it still takes longer than your thinking allows you to be comfortable with.
I always use (as Trigger states above) Graphogen for all plain bearings when building an engine, the principal difference from just oil is that is stays coated on the surfaces even if there is a long period between building and using the motor. It will prevent any pickup with the bearings until the oil arrives.
Presume you have the spark plugs out to reduce crank loading?
Could try tipping on its side to fill the gallery via the plug with oil. I've never tried on one of these but you could also raise the rear and fill the oil filter housing without oil also and bolt it back on with it filled as much as possible and the filter as level an you can get it.
Spitfire:
I had the same problems with mine after a top end rebuild http://www.sohc.co.uk/index.php/topic,1573.msg1729.html#msg1729
This was what I said at the time:
Took a long time to get the oil pressure light off, I put one litre of oil in the tank and one litre in the cam cover, it took a long time for the oil light to go out, so long that I started to suspect the oil pressure switch, but a look into the cam cover showed no sign of oil spraying around so I carried on. The oil light eventually went out, then I waited a few more minutes turning her over until I could see oil spraying about in the cam cover. Plugs in and she fired up on the second push of the button.
Cheers
Dennis
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