Oil flow problems

[JOOLZ]

This is the second time this has happened, the flow of oil to the head has just stopped, no reason. plenty of oil in the tank, system was bled after the rebuild and I have since done 300 miles, last night I noticed the temperature was going up so nursed the bike home 
I have read and reread the manual I have looked on the internet where I read stories of XR's and similar models having the same problem and damaging the head and cam. I just cant seem to locate the problem and I am at my wits end. Any ideas suggestions are welcome

[SteveC#222]

Blimey Joolz you probably know more  about these engines than most of us! From my bodgers point of view if you have no flow at all it must be either a blockage/airlock or something wrong with the pump.  I know the XBR can be a pig to bleed if it gets an airlock - luckily it hasn't happened to me - but I'm sure you know all about that. I know it's stating the obvious but

Blocked filter / screen?

blocked oil line?

Is the filter cover on the right  way - oilways lined up?

Pump within spec or not blocked

Unions/banjo bolts blocked or damaged?

Do you have an oil cooler? - something blocked in there?

Hard to say really. I always start with the silly stupid things and work up from there, but it's often something silly.

[Nell]

It's a long shot but I had a similar problem a few years ago, the cause being the screen filter in the oil tank was almost blocked with pieces of soft black carbony material restricting flow to the pump. Don't  know where it came from but no problems since.
This was the last resort after carrying out all the other checks and a real pain to do as Honda seem to have taken an oil tank off the shelf and designed an XBR around it.
 

[JOOLZ]

Thanks for your input, Im sure I dont know much more than most about these engines, but I am always learning.
I cleaned out and rebuilt the oil system 6000 miles ago with new seal etc.
With my engine running the crankcase in a vacuum maybe there is somewhere it is leaking enough air into the system to cause problems without leaking oil out.
Anyway I think I will go through the whole thing again. There does seem to be a fundamental design problem with the oiling system on RFVC engines

[Propellor]

Is the low flow to the top the cause of the overheating, or a result of? Makes you wonder.

[SteveC#222]

I learned a long time ago to loosen off the banjo bolt on the cylinder head oil pipe union when you start up after a full oil and filter change until the oil starts to trickle out just to make sure it's circulating.

[JOOLZ]

I know all about opening the banjo on the head when bleeding the system. The system was bled through and worked fine for 300 miles but it just stopped coming back from bike night last Thursday.
Its odd as I removed the head pipe from the clutch cover and kicked it over a few times and I get a few splatters of oil and lots of air, I then removed the oil filter and repeated the process and there seems to be plenty of oil coming into the chamber where the filter sits, its almost like the pump cant push the oil further up the pipe into the head I have checked the pipe and it is clear.
Its looking more like a problem with the actual oil pump not delivering the volume or a lack of pressure, but as I say I checked the specifications on the pump when I rebuilt the bottom end and replaced the seals.
Next job is to remover the clutch cover and take out the pump again and have a close look at it

[JOOLZ]

Interesting page here about oil flow problems   http://www.advrider.com/forums/showthread.php?t=552341&page=3

[SteveC#222]

If it was working OK prior to the last rebuild then it must be connected to the rebuild. Sounds like Honda used the same pump on the 650 engines so it should be able to cope with the required volume but it's not pumping at all or intermittently. If you have no obvious external leaks then I would have thought it must be either a faulty pump/seal/gasket or restriction in supply to the pump - could one of the mesh strainers - possibly the one in the oil tank?  or maybe a problem with the return feed.

Was oil returning to the tank?

It's a bit of a mystery.

[JOOLZ]

I cleaned out the mesh strainers at the last rebuild, oil is returning to the tank ok, Im starting to suspect an intermittent internal leak somewhere

[JOOLZ]

I checked my head and cam, thankfully they are ok. I have been really researching the oil pump problem, and have concluded, it very rarely fails on a normally ridden road bike but does affect bikes use in anger in motocross, desert racing and hard revving hard accelerating road bikes, I think its pump cavitation as well as a restricted head feed pipe are the problem, I have removed the banjo s from the bike and replaced them with 2, 8mm x 1.25 spigot and some big bore hose. I will see if this solves the fault

[Propellor]

If it's cavitation would an elevated oil tank cure it?

Or is there a valve in the suction line, to stop wet sumping, which is causing a restriction? It seems strange to have cavitation given there is a reasonable head on the suction side?

Would a high oil temperature be more prone to cavitation? I think temperature does affect it.

[Propellor]

http://www.engineeringtoolbox.com/cavitation-d_407.html

[Propellor]

Hi joolz.

I don't know what your own thoughts are, but realistically, if cavitation is the problem, the two main things you can change are the suction head and/or the oil temperature. You could try a bigger bore suction pipe and remove any restriction in the suction line.

You could try to increase the suction port into the pump, but you are into a dodgy area here!

Let us know your own conclusions.

Cheers and good luck.

Edit:when you say "head feed pipe" and "big bore hose" , do you mean the delivery to the cylinder head, or delivery to the pump?

[JOOLZ]

Thanks for that info,  I dont think raising the oil tank would solve the problem, XL and XR's have the oil in the frame so should have a greater head of pressure to start with.
I meant the delivery pipe to the head, RS 600 flat trackers all ran a big bore feed to the head
I think the problem lies at the pump, it needs to be larger running at a lower speed, spinning a standard pump faster would lead to worse cavitation problems I think