Ariel Owners Motorcycle Club

Guys,

Having fallen foul of the split pin getting wound up in the spring and allowing the ball to come off its seat (thank goodness for the pressure gauge!) my SQ4 now has a cable ferrule over the spring, to stop the spring getting caught. The ferrule is drilled out to the inside diameter of the spring.


I wrote about it here:

https://ariel-square-four.blogspot.com/ ... t.html?m=0

Further testing this morning.

I have tried Sime’s solution with the ferrule, which seems much better than just the split pin holding the spring.

The bore on the ACME valve body is larger than the one from Drags.

I don’t have a compressor where I can regulate the pressure, so I can only use the bicycle hand pump.

First step was to make sure the valve is actually closed by blowing on it in my mouth. They both seal. BTW I googled what pressure can a human reach by blowing and it seems to be around 2psi max. So not really much.

On both valves, if I push the plunger on the pump slowly, then the air just slips through with no pressure buildup. However, if the plunger is pushed down vigorously, then pressure goes up to about 30psi on the ACME valve and 40psi on the Drags. On the ACME one, there is a distinct change in tone when the max pressure is reached. On the Drags one, not really.

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.

Now, is this normal? 1. Because of using air and not oil? 2. The way the bicycle pump works, in that it doesn’t hold the pressure? 3. Something else I’m not seeing?

Hmmmm….

You might understand my concern after what happened with my engine. I put it down to the valve not sealing, dumping the oil into the crankcases and having no pressure at running temperature. That’s why I want to be absolutely sure my valve works before building it in.

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 took a few kicks for the oil pressure to register on the gauge.

A few kicks more and oil was dribbling from the OPRV. More kicking produced more pressure on the gauge and more oil out of the OPRV. I stopped kicking and the gauge returned to zero and no more oil exited the OPRV.
I repeated this several times, checking the pressure at which the OPRV opened and ensuring it closed. When all looked ok, I refitted the cap, put the spark plugs in and started the engine. (In an earlier post.)

So far, so good......

I'm not claiming that this is a foolproof test, but with all the dry testing you have done so far and fitting the ferrule over the spring (I like that, Simon and will retro-fit one to mine,) you will probably be as close to sure about your OPRV as you can be, other than doing what I did as a further test. If the 'wet test' throws up a problem, it's easy enough to remove the OPRV and ...well, try again with another one?

Coming back to Paul's observations about the spring, I have bought two from the usual supplier (at two different times) and one is considerably longer than the other. I also bought a new OPRV body from them which wouldn't screw into the crankshaft. Add to these 'variables' the fact that the Acme valve bore is larger than the Draganfly one, it's no wonder that there's a lot of head scratching going on!

Gui.dorey wrote: ↑Sat Feb 25, 2023 9:36 am
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 earlier post.) I was just wondering if the loss of pressure when stopping pumping could be due to the pump connector....(ok, I'm clutching at straws again....)

I think the fact that the pressure returns to 0 psi when you stop pumping has more to do with your test rig than the valve. A tyre pump has hardly any volume and gases will find the tiniest hole and leak out of it, losing pressure fast.

An option might be to add some volume to the rig with a tee and something like a football (or an air mattress!) or perhaps more simply to partially fill your tyre pump with water or oil (to provide a huge increase in the viscosity of the test fluid), and control the pressure by leaning on the pump? You could perhaps see when the valve opens and closes, as the liquid should allow you more time to observe what's happening.

Gui,

It sounds to me as if your oil pressure relief valves are working correctly. I don't think you will ever replicate the performance of the valve in oil by using air and you certainly won't replicate what goes on in the valve when it has oil in it at the Square Four's running temperature. So my test jig is only going to be an approximation. In the absence of a compressor though, you might like to go down to the local petrol filling station and try the valves using their tyre inflation / checking facilities.

I have gone back over your account of the failure and the thing which jumps out at me is that you said that when the engine is hot, the oil pressure drops to zero psi, even when going at riding speed. There has to be a problem here. I have seen a Square Four or KH drop to zero pressure many times at tickover but blip the throttle and you are pretty soon seeing the needle come up off the zero mark. So why would the pressure drop to zero and stay there? We know there is a problem of the sump filling with oil so could it be that this causes the oil level to drop far enough in the tank for the feed pipe to become uncovered and air sucked into the feed pipe? Would this lead to a need to re-bleed the Morgo pump to get it to work properly again?

The partial blockage I had on the Healey scavenge pipe caused no end of strange happenings on the oil pressure side, although probably magnified by the very different oil tank on the Healey.

I do wonder if you have a blockage or partial blockage in an oil pipe somewhere. The junction block on the oil pipes which bolts onto the crankcase would be a favourite place for something like a tiny piece of rag to get stuck and restrict the flow. I suppose you might get a similar result if the inlet and outlet pipes to the full flow oil filter on the return were the wrong way round.

None of this gives you an answer, but I hope it might prompt some thoughts either for you or for others on the Forum to share with you.

Thank you everyone for your inputs. I think I shall just have to test the valves on the engine and see how the pressure behaves. To Allan - look a few post backs and you can see pictures and a video of the test rig.

To Paul’s considerations, I did check all the oil lines for blockages and never found anything. I had plenty of oil reaching the engine and the rockers. The was a good flow of oil back into the tank and the level never dropped so much as to uncover the feed pipe. The Morgo never showed any air bubbles when I undid the bleed screw, which Idid more than once. I had also checked the sump scavenge pipe, and now again with the cases disassembled, and it was clear, well fixed and no cracks. I re checked all the passages in the cases and all were clear and clean. I also went through all the sludge traps and oil passages in the cranks, and they were all clear.

So, really the only thing left was the OPRV. Maybe there was some debris keeping the ball off its seat, but who knows now. At least I didn’t find anything. At the moment I really don’t have any other explanation for what was happening.

Again to recap what was happening:
Using 20w50.
On cold start, oil pressure gauge needle jumped to the stop and stuck there for a while.
As the engine warmed up, the needle would slowly start to drop. After maybe 10kms it would be at 0 on idle - it may have moved a little at speed, but just a blip.
Crankcase would always fill up with oil, and there was permanent good flow of oil back into the tank.
The nr 3 rod definitely seized (the shells on the big end showed clear evidence of this), so it didn’t brake due to material fatigue. The sludge traps and oil passages in the cranks were spotlessly clean.

Do you know what the main and big end bearings measurements were?

My Morgo-equipped Mk1 goes to about 70 psi when cold - but that's purely down to the spring I have vs. the spring you have. What I'm curious about is why your pressure dropped so low when hot - mine never goes below 15, even idling hot after a fast run.

Thinking about this further, and to Simon's point just now, if I rule out the OPRV being the problem, oil could only escape to the sump and causing the pressure loss through the plain bearings. They would have to be quite worn out. The manual gives a clearance of 0.001-0.005in. I don't remember what clearance I had, and stupidily didn't think to measure it now when I assembled the cases. However, I believe the rear one had maybe 0.003 and the front one less... The plain bearings were new, but I turned them to size myself, so I could have gone a tad too far with my skills...

A while ago I posted this video showing the engine running without the timing cover. My question was if anybody thought the amount of oil flowing out of the rear plain bearing was normal. There wasn't a definite answer, as nobody seemed to have tried running the engine without the cover. But here it is again. Also a second one from the first time ever after the 1st rebuild, where the cap for the front crank is off. One can see some oil flowing out of the front plain bearing as well, and not really from the OPRV, it seems. Both videos were taken immediatly after a cold start, so the oil is still cold.

Who knows, perhaps new thoughts... although I cringe at the thought of having to fit new plain bearings again....

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 said about the full-flow filter possibly being connected the wrong way round, would you please remind me whether you have an inline oil filter fitted and if so, is it a Norton Commando-type or a Morgo one?