Not that I'm feeling bitter, but ahhhh, just put in some 20w50 and the oil pressure is still dropping to zero and back up again, I'm seriously thinking about selling her/it as spares or repair.
If it is the relief valve and as there's room around the valve should I be thinking of adapting one say out of a descent motor bike ?

maybe you have the problem I had and probably have again. They repaired some blockage in an oil passage apparently it was a known issue because Jason at CFmoto seemed unconcerned and very matter of fact that this was a common issue. He was very unconcerned with all the issues I had actually.

Do you know which passage way ? I can't see that as being the problem I rebuilt mine 1000 miles ago and it's spotless inside

[2015 Z Force 800 53/Trail EPS]

Well, IMO you just proved the rod bearings are NOT the problem...in fact you just proved that the problem is before the pump, not after it. So..it's having a problem getting the oil. Could the screen be blocked? or something oil intake-related? Pulling some air in too it seems. Maybe a pump shaft or cover seal..something like that?

Well, IMO you just proved the rod bearings are NOT the problem...in fact you just proved that the problem is before the pump, not after it. So..it's having a problem getting the oil. Could the screen be blocked? or something oil intake-related? Pulling some air in too it seems. Maybe a pump shaft or cover seal..something like that?

I was just thinking it can't be the relief valve as the pressure drop happens at different pressure's.
Now you mention it I have to fill the oil very slowly and let the oil settle before continue filling, so I have to pour in a bit wait a bit until full. I wonder if the passage way between the two casings is restricted somehow, or as you say the screen is blocked. It would explain the rise and fall if the pump is being starved of oil flow somehow.

I think I may start by pulling the right hand cover off

[2015 Z Force 800 53/Trail EPS]

Well, IMO you just proved the rod bearings are NOT the problem...in fact you just proved that the problem is before the pump, not after it. So..it's having a problem getting the oil. Could the screen be blocked? or something oil intake-related? Pulling some air in too it seems. Maybe a pump shaft or cover seal..something like that?

I was just thinking it can't be the relief valve as the pressure drop happens at different pressure's.
Now you mention it I have to fill the oil very slowly and let the oil settle before continue filling, so I have to pour in a bit wait a bit until full. I wonder if the passage way between the two casings is restricted somehow, or as you say the screen is blocked. It would explain the rise and fall if the pump is being starved of oil flow somehow.

I think I may start by pulling the right hand cover off

Yeah, if the returning oil isn't getting back to the pickup fast enough..it would break suction and become very erratic. And I don't have to go slow on filling it with oil...it takes it as fast as I can pour it in.

yeah I can't, the first litre isn't bad but getting the rest in is a bit slow

I am not sure as the tech comments were just.. crap...

If you figure it out you will probably enlighten a lot of us having the same issue.

If you figure it out you will probably enlighten a lot of us having the same issue.

Yes I will

Why can't it be the relief valve?  A collapsed or weak spring could cause the seat to bounce (flap) around causing erratic oil pressure.  Maybe the valve is stuck open and most of the flow is returning to the sump.  The oil pressure that you are seeing is what the relief passage cannot handle.  I really have no idea.  Just throwing stuff out there.  Was there debris in your strainer when you had the cases apart?


Related story.....I helped change an oil pump on a small block Ford.  After it was back together we started the engine and the oil filter exploded in about 2 seconds.  It blew apart at the seam.  We changed the filter thinking it was defective and started the engine again.  Boom! 2 seconds.  Outta here.  I think the starter was still engaged thats how quick it over pressurized the filter.  We ended up pulling the pan and taking the oil pump off thinking it was a bad relief valve.  When we took the oil pump cover off there was a piece of oil pan gasket stuck in the valve holding it open.  We removed the debris and put the truck back together.  Ran fine for many years until it was sold.  Just some food for thought.

yeah I can't, the first litre isn't bad but getting the rest in is a bit slow

Mine is the same way.

Mine takes oil as fast as the funnel - hose thing will empty.

I must be coming into this problem late and it must have been a discussion in another thread because the first post in this thread starts with '...the oil pressure is still dropping to zero '

Which obviously raises a tom of questions such as how is the pressure being measured, with a manual gauge at an oil gallery test point (where the 'oil pressure switch' is per page 191 of the service manual) or via the machine's own 'idiot light'? Does the machine exhibit any signs supporting a conclusion of low oil pressure, such as excessive noise? It's probably been discussed but I can't see where.
Is the switch/sending unit faulty?

Putting thicker oil in the motor seems like treating a symptom rather than the problem.
I doubt whether too slow returning oil is a problem as it looks like most of the oil returns to the sump via the central crankcase space and not via an outside case. The likelihood that the oil is returning to the pickup point too slowly, causing the pump to cavitate, appears unlikely. There just iisn't enough space in the top ends for 3.4 liters of oil to occupy, for this to occur!

I guess I need to read the thread that contains the history of this failure.

Mine takes oil as fast as the funnel - hose thing will empty.

I must be coming into this problem late and it must have been a discussion in another thread because the first post in this thread starts with '...the oil pressure is still dropping to zero '

Which obviously raises a tom of questions such as how is the pressure being measured, with a manual gauge at an oil gallery test point (where the 'oil pressure switch' is per page 191 of the service manual) or via the machine's own 'idiot light'? Does the machine exhibit any signs supporting a conclusion of low oil pressure, such as excessive noise? It's probably been discussed but I can't see where.
Is the switch/sending unit faulty?

Putting thicker oil in the motor seems like treating a symptom rather than the problem.
I doubt whether too slow returning oil is a problem as it looks like most of the oil returns to the sump via the central crankcase space and not via an outside case. The likelihood that the oil is returning to the pickup point too slowly, causing the pump to cavitate, appears unlikely. There just iisn't enough space in the top ends for 3.4 liters of oil to occupy, for this to occur!

I guess I need to read the thread that contains the history of this failure.

I deleted the first post as someone started talking about ethics.
Anyway the engine was rebuilt 1000 miles ago after suffering a big end failure on the rear cylinder, she was running fine and still is but after changing the oil to fully synthetic when at running temp the oil light started flashing consistently, so I picked up an oil pressure test kit and fitted it to the port for the switch, she was warmed up and revved to 3000rpm were she peaked at 35psi only once she spent most of the time rising and falling between 20-30 psi, I then brought her back to idle where she ranged from 0-12 psi rising and falling all of the time   

...I then brought her back to idle where she ranged from 0-12 psi rising and falling...

If I'm reading it right, the chart on page 191 says oil pressure in the warmed up CF 800 (converted from KPa to PSI) should go between 0 and 11.5! And between 50-61 PSI when revved to 6000 RPM. I didn't see you having tried for a 6 grand reading but... Somebody else take a look and see if I'm missing something?

Because in that event yours might be acting as designed, maybe nuttin' wrong at all.