Looking at the second video, could it be that the oil is coming out of the timing case drain hole into the sump, rather than from around the t/s bush? If that were the case, it suggests that the sump oil level is too high. Could this point to a scavenging/oil return problem? Thinking about what Paul...

So it would seem both work and open at somewhere in the range of 35-40psi. However, what puzzles me is that the pressure then drops to 0 once I stop the pump. Which leads me to believe that they don’t seal again. Is there a tyre valve fitted to your test rig, Gui? (Sorry if this was mentioned in an...

Gui, When you've tested and fettled the valve as far as you can go, I would still test it in-situ when the engine is assembled back in the bike and the oil tank is full. On my bike, I removed the cap on the front crank and then used the kickstart to turn the engine over. It surprised me that it only...

Johnny's comment echoes my question about the use of seals, but Mike's post has answered it precisely. Thank you both.

The seals are designed to allow some oil to pass to provide lubrication, which sounds right.

I've seen a picture somewhere on this forum. I'll try to find it later, if I get a chance. Viewing the OPRV from the 'open end,' imagine fitting the ball and spring and split pit. Whilst the split pin legs are still straight, insert a small screwdriver or whatever between the legs inside the hole in...

Can you introduce some oil to lubricate it and try again? I do wonder if using just pressurised air is a reliable test. Air is not exactly viscous and may behave differently to hot or cold oil. Also, there will be friction inside the OPRV where the spring can kink and contact the body. Perhaps if o...

So if that is the case on a 4, how do they regulate a different pressure with the same valve? I've read somewhere that stretching the spring (yes, really!) will increase the amount of preload and thus the force acting on the ball when it is fitted into the OPRV.* On Norton twins, the (much larger) ...

I'll have a word with my retired machinist friend. He'll tell me if he has the tools for the job.

Looking forward to your reports on carb and ignition.

Allan.

Hi Frank, I've realised one important fact. The o.d. of the valve guide is 14.1 mm. The i.d. of the inner valve spring is 16.3 mm (quick measurements with a caliper.) Therefore, there is no room for a seal around the top of the guide. The tops of the guides will need to be reduced in diameter so tha...

Ah, I see, that explains the need for the special cutter. I've found VGS' website now https://vgs2cv.be/en/tool-klep-seal-AZ-M4-p531340456 and the special cutter, as shown in the video. I'm hoping that I will find some suitable seals which will be the right size for the Square Four without the need ...