oil pressure to crank

[al.bell]

I’ve owned my ’35 Red Hunter 500 three times since 1972. In the 1970s I put a new big end in it but never ran it and sold it to a mate when my marriage went south in the mid 1990’s and I needed money. He got it going and rode it on rallies, then sold it back to me when his marriage broke down in 2004. I cleaned the flywheel traps etc and rode it on several rallies. I don’t imagine the rebuilt motor had done more than 5000 miles before developing big end knock. I pulled it down. The oil delivery hole in the big end pin was blocked with debris – seemingly from the bearing and cage. The pipe which delivers oil from the timing cover (oil pump) into the crankshaft is a very loose fit in the shaft. There’s about a millimeter of space around it. Is there a bush missing there? Some say it’s supposed to be loose and the oil is delivered by being squirted in the general direction of the crank, then forced into the bearing by centrifugal force. This has always struck me as a weakness, and the problem (of the hole getting blocked) seems to bear this out. The fact that the hole(s) in the pin are the narrowest part of the delivery line also seems to invite blockage at that point. I’m tempted to try creating a bit more pressure into the bearing by making a bush to limit the leakage between the shaft and the delivery pipe. The obvious concern is that the location of the timing cover and hence the centering of the delivery pipe in the shaft is hardly precision and never could be. There is an oil pressure indicator on the outside front of the timing cover. This seems incredibly optimistic considering the situation (heaps of space for the pressure to leak) on the crankshaft side of the pump. I’ve never seen any evidence of “pressure” on my indicator and didn’t expect to, but my buddy tells me his ‘37 VG shows pressure on the indicator when it’s cold. I’ve scoured the net without success, so I’ve joined this forum to raise this topic – sorry I’ve been so long-winded. Any response / poinion / experience greatly appreciated

[pete.collings]

I have recently come across two motors with failure of the oil feed quill. One had a quill that had cracked, limiting the feed of oil to the big end, which was filled with hardened deposits and had failed. However, it had done around 30K miles, so not too great a loss, it was unclear if the deposits in the big end had build up before or after the quill failed.
The other was broken off, as a result of the crankpin nut sheering and presumably allowing the crank to flex and putting strain on the quill.
Thus I would be wary of putting any bush/sleeve into the mainshaft to reduce the quill/shaft clearance, as any flex or slight misalignment of the crankshaft could increase the likelyhood of failure of the quill, which would have disasterous consequences to the big end.
My understanding, as outlined by Al, is that the centrifugal force of the flywheel pulls the oil towards and out of the big end. I always ran my singles on monograde 50 oil, a thicker oil is less likely to seep out where it should not. It is also possible that the oil pump is not working at full capacity, some wear on the feed plunger/bore can allow oil to seep out of the top of the pump when working. If there is oil in the feed side, cover both feed holes with your finger and pull the plunger upwards. You should feel some resistance, and the plunger wants to pull back when released. This is not a foolproof test, but gives an indication of the condition of the oil pump.
The debris in the crankpin oil feed holes could be as a result of other oil feed problems causing the breakup of the bearing. Ariel single oil pumps can often cause problems if a bit of muck gets stuck under the non return ball in the pump, more often this is on the return side, causing the sump to fill with oil, but if the oil is dirty it could affect the feed side.
The crankpin oil holes are fairy small, but I have not encountered problems with them blocking, cleaning out the crankshaft sludge trap should keep then clear. Modern oils don't have the sludge generating properties of oil 50 years ago, so the trap should not need cleaning very often.
Finally, the parts lists show there are two different quills, whether the later one 2080-41 has been fitted to your 35 model, or indeed what the differences are between earlier and later, I don't know.
These are my experiences with the later postwar singles, perhaps others with experience of prewar singles can advise.

[brenton.roy]

Hi Al,
Welcome to our forum. Where are you from?
The quill is stepped - do you think it's that much clearance?
It's often hard to tell how much of the crap caused the failure and how much resulted from it.
You could fit a later (larger capacity) oil pump to deliver more oil.
I agree with Pete. The remains of your bush might well create the big end problem you're trying to cure.
Also, to stay with good oil. Although you have owned the bike for a long time, you may not have done all of the servicing? The detergent in multigrades will move sludge that was quite happy to stay put with an older oil. Much of it will stay in suspension (and so, via your bearings). For that reason I change oil at short intervals. An alternative is to fit an aftermarket oil filter.
Things like sandblast grit and crap in the oil tank will eventually hit your big end. This is Murphy's law.
There are a couple of posts that mention rust pitting on bearing surfaces, due to condensation. 5000 miles over 40 odd years isn't much - and so this is a possibilty.
regards, Brenton

[al.bell]

Thanks Pete and Brenton for your fast and helpful response. I'm in Australia - the most Easterly point. From now I'll call the pipe a quill. It's not stepped on my bike, but the bike was being thrashed as a speedway trainer when I got it in '72 and has a lot of parts incorrect. I will certainly consider fitting a later oil pump if it can move more oil. I'll do everything I can think of to get the oil tank clean - including frequent oil changes. I'm advised is to only fit filters on the return line with these old plunger pumps - which is a bit like closing the door after the horse.... The holes in the tank filter gauze aren't much smaller than the holes in the big end pin so it's easy to imagine how debris can get to all the wrong places. Murphy's Law always applies - even O'brien's Law, which states that Murphy was an optimist - but I'm pretty confident that no-one has ever come near my bike with a sandblaster. If they did, they covered their tracks very well. I can proudly say that even though it's far from original, the machine has never suffered any cosmetic intervention. Alistair

[david.anderson]

Al
The big end itself is not subject to any oil pressure, but actually gets the bleed off oil from the oil pressure regulator. Theory has it that being a roller bearing, the bigend does not need a lot of oil. A few dribbles coming down the mainshaft should do it. Yes the gap around the quill is correct.
The oil pressure regulation happens as soon as the oil leaves the pump into the timing cover. The oil pressure is created to force the oil up to the rockers which on 39 and later singles are only fed through a pinhole at the entry to the banjo on the end of the external oil pipe. (not familiar with top end oiling pre rockerboxes) When the oil pressure builds up to the set pressure (which in your case is adjustable) a ball valve blows open and allows the oil to feed through to the bigend. So the advice about upgrading the oil pump to the later larger delivery plunger pump means that the rockers get the same amount of oil and the bigend gets all the extra oil (which is flung around as it exits the bigend to give extra lubrication to the cylinder and bottom end). My fathers advice to me about his 49VH (small plunger oil pump) was that he got 10,000 miles each from his first 2 bigends. After upgrading to the larger plunger pump bigend life went to over 50,000 miles. Draganfly provide exchange upgraded oil pumps.
My 49VH pumps at 12- 15psi.
An oil filter in the return line is a good idea. Fitting to the return line is not a matter of after the horse has bolted as it is actually the first place to catch contaminants and should keep the oil tank clean, ie the supply. I use filters from CRF250 Honda that are fitted into a filter holder that I made. The Norton Commando oil filter set up is used by many people with older bikes.
David

[nevhunter]

As you state, roller bigends don't need much oil. They only get a . miniscule amount in two strokes. The quill can have a fair bit of clearance as any oil that runs along the inside of the mainshaft will centrifuge past the sludge trap to the bearing. The oil pressure indication ( IF Fitted) does not indicate pressure to the big end. It provides oil to the rocker gear and indicates that the pump is working on the models that have a gauge fitted. Setting it up for a high pressure only loads up the pump.
The VH big end is usually fitted with an aluminium cage but unless you are revving it you could use crowded rollers like all the other models do. The big end if it is made from good metal should do 15,000 miles. I have seen one that did over 100,000 miles with the original big end, but it was not used hard. 1939 model, one owner till the son took it over. The VH bigend and rod is considered a pretty good one. Conrod alignment is important. Nev

[brenton.roy]

Hi Al,
your '37 only gets oil mist to the inlet guide, and grease to the rockers. On this subject, there is a conversion I've seen that directs oil to the rocker shafts. This might be worth looking into. I will be doing the same.
Re the quill (2080-41), which may be different for a '37? - for the timing case I'm looking at, the quill is narrow along it's length, but thicker where it goes through the cover.
Doing a rough measure, the step in the photo is quite close to the opening in the mainshaft, and is a little larger in diameter than the bore. It will likely stop some backflow.
The shape of the inner casting of the timing cover suggests that a some oil could make its way onto the crankshaft from around the cam - although the flow is likely in the other direction.
David and Nev are both on the east coast.
regards, Brenton

[ian.scott]

Any chance of publishing the details of the exhaust guide oiling as I'm planning on drilling the head and guide and fitting a bleed off the oil pressure gauge over the winter.

Ian

[nevhunter]

Grease to the "open" rockers is fine, for the spindles. Regarding the oil feed to the inlet guide the normal way is through a fine bore copper pipe from the crankcase via a simple hole. The inlet guide would "suck" some oil along the capillary pipe, as there is always some suction there. Some bikes in the mid 30's had grease nipples to the valve guides. My daughter ran a 250 ohv BSA that was greased on the inlet only and if it was greased a small amount each day, there was no wear. ( very satisfactory).. Nev

[brenton.roy]

Hi Ian, I'd love to, but have only seen this on a bike found parked. I spoke to the owner and he was quite happy with it.
It was a pressure feed, but how much pressure, I couldn't say. Nev's idea sounds good.
Brenton