Hi guys
Just reading the workshop manual on my a65 1967 engine and it states the con rods have to go a certain way round , I've fitted the caps to the corresponding numbers but didn't know they go a certain way round . So how do you identify which way is the right way
Mark
Hi Mark,
Does one of your rods have small hole through from the journal to the side of the rod? This is the lefthand or drive side rod. The hole faces the crank so the numbers will be to the left and to the rear looking at the crank with the drive side to the left. The hole is meant to allow a bit of oil to squirt on to the crank which then gets flung up to help lubricate the piston, small end and bore to some extent.
I think it is also intended to equalise the pressure in the big ends. The timing side journal will get the pressurised oil first and by the time it gets to the other side the pressure has reduced so by putting the hole in it reduces the resistance to the oil pressure thus balancing it between the journals, well in theory at least.
Dave.
It started as a theory to stop motors breaking, it wasn't until they got rid of the 4CA points (or rather the 4CA points cam) that this stopped. I don't believe A10's ever had this hole and it's never been an issue. My Lightning has the hole in for the left side rod (thunder engineering rods) but the rods for my bored and stroked A65 doesn't. But if yours have the drilling the hole should go to the drive side as Dave mentioned.
For orientation, obviously the caps need to line up and the numbers help here, the numbers in theory should face forwards (I say in theory in case they have been stamped on the wrong side) to be more precise the tangs on the shells should be on the same side of the rod as each other and both tangs should be at the rear side of the crank.
Except for the very early A10s all A10s and A7s had the small hole in the drive side con-rod. It was to force some lubrication on to the nearside bore after problems with that side nipping up.
Hi,
The A10s had this hole and if it was later considered unnecessary then it was just carried over to A56s as a just in case. There does seem to be tendency for left hand journals to wear a bit more than the right. This is made worse when the sludge trap starts to get blocked and the flow to the left hand journal is potentially reduced.
I used to have a camping stove with a grill and in order to get even grilling the holes in the burner started off being like a pin prick and gradually got bigger as the burner got further from the gas inlet.
I suppose, in theory, if the hole is not there then an extremely small amount of wear on the left journal would have the same effect as there would be little less resistance to the oil pressure.
Dave.
Hi,
Worth a read, I guess it would be prudent to have a rod with a hole installed correctly:
Best wishes...
Thanks fellas I've looked and I can't see any holes but I'll make sure the numbers face backwards when fitting
Sorry numbers facing forward
Hi Mark,
Engines after Feb 1965 should have the lub hole in the con rod when supplied by BSA. If not it is suggested a hole is drilled when being overhauled.
Best wishes...
Just for Information only.. I'm NOT saying you should do this but I've previously re-built my 1971 OIF A65L and now I'm just working on my 1970 Firebird and I've found the drive side rods on both to have 2 holes drilled. Pictures are of both sides of the Firebird DS rod which was removed yesterday.
Interesting. It looks like BSA put a single hole as discussed, then stopped and then started again but with two. Obviously to make sure enough oil gets to the left hand side. Having these holes would also increase the centrifugal effect of the rotating crank drawing oil through regardless of oil pressure. Higher revs means more centrifugal force so more oil drawn through.
Perhaps not quite so important with an end feed conversion but with the standard bush I would think a definite plus.
Dave.
If you are thinking of drilling a hole in your con-rod, the hole size is 3/64". You will need to drill at an angle to finish up in the centre of the big end eye so as to line up with the hole in the bearing shell. Good luck with that!
Hi,
The second hole added to the OIF models lubed the roller bearing on the drive side:
Best wishes...
My A50 is a 1970 (last in the line) and that has two holes.
I'm still not convinced with the oil holes benefits to be honest. An example of a new rod not having a drilling is MAPs H beam rods, these types of rods are used in NASCAR but a lot of racing guys (BSA and Triumph twins) use these rods. They don't have the hole... they do have the small relief on the side of the rod which is supposed to do the same thing, but that is more for oil spray direction, there is plenty of oil flow through the journal/shell, there has to be otherwise the oil sandwiched between the shell would fail very quickly.
I think that if BSA had not considered it a good idea surely they would have stopped ding it. The operation to to drill these holes would have cost money so why do it if not necessary. Do Carrillo rods have the hole?
Dave.
I've just spent some time looking at Corillo rods but sadly none of them stated A65, however non of the rods I did see had the hole either. I think we have to remember that BSA had a lot of warranty repairs on these engines that I think they would try anything.
Yes they did have a few reliability issues but these holes had been on all but the earliest twins and other makers did the same. I think Norton had similar holes on some models so the belief that they were of some value seems to have been industry wide but sometimes one does it and the others follow just in case.
It would be interesting to see what difference the hole makes to the flow to left hand journal as well as the oiling of the left hand cylinder but how it could be measured I do not know.
Dave.
This thing about the oil hole in the left hand con rod has come up on variuos forums. As I understand it when the A65 was first introduced in 1962 it did not have the oil hole but BSA was recieving reports from dealers of seizures and partial seizures on the left hand cylinder so they started putting in the oil hole this had already been done on A7 and A10 engines for quite a number of years previously and was done to improve lubrication of the left hand cylinder. I have seen a copy on another forum of an instruction that was sent out to dealers intructing them that if a bike came in and had to be stripped right down for major work then the modification was to be carried out but they did not intruct dealers to carry this mod out on all bikes. So it is possible that some early bikes will not have this mod carried out. My own bike is a 1963 model but left the factory in October 1962 and has the mod done also my bike is still cmpletely standard and has the original pistons in the were fitted when it left the fctory.
Have a '71 Lightning and the drive side con rod definitely had 2 oil holes
I've copied this from Mark Parker on Britbike.com; for those that don't know Mark's A65 is bored and stroked, it has his own modification off set 90mm norton crank and I believe B44 pistons, within A65 cases and mounted in a cagiva frame, this bike puts out more HP than any other twin of a similar capacity...
Quote from: Mark ParkerI've taken a rod from my motor when I first got it, (and it had done a lot of miles) and the rod was split exactly up the oil hole drilling to under the L/End which was only held by half the rod beam it definitely weakens the rod, I don't think they fail there usually but for some reason this one did. I think the rod was drilled so it had a little hole in each side and it was like a cutaway showing the drillings where it broke. Thats why I think the little grooves in the upper thrust faces would be a better option to get oil up the bore if you wanted more oil thrown that way. The BSA race rods which are the same as late uppers only with steel caps I put in it had no holes, I would use a rod with a hole or holes, but I wouldn't bother drilling a rod that didn't have it. They might have had that hose idea in mind Nert but the oil gets out past the bearing anyway and the system won't pressurize till oils filled the crank and i have good pressure building on the first couple of kicks if not the first kick when I start mine without the hole.
Incidentally I was looking through pics of my A65 from when it was first rebuilt (back when I knew nothing about these bikes and had someone do the work for me) the bike had a pre 70 rod in it and a post 70 rod (the late rods were about 17 grams heavier and shot peened) only when I was scanning old pics the other day I found out that what it had was two drive side rods so they both had the holes this would be similar to there being no holes, it was never a problem. New rods were fitted because the bike was getting some abuse and I wanted new rods to help strengthen the motor.
As I mentioned earlier the seizure problem was later cured when they changed to the 6CA points, the long dwell time (170 degrees if I remember rightly) was good for power but bad for points bounce it was this rogue spark from the points bouncing that was causing the seizure issues... it wasn't cured by drilling holes in the rod, they simply reverted to what the pre units had and worked on them, but pre units were fitted with magnetos and not points and they work differently.
Hi,
I think Mark Parker sums it up. If your rods have holes use them and if they don't, do not drill them.
I would not set any great store in the fact that race rods do not have holes as race engines had to last a couple of races before being rebuilt and the minute reduction in strength was not worth the risk on a highly tuned and stressed engine. Some race engines were built with 'wear' tolerances so that they would not seize and did not need much in the way of running in.
Only high mileage will determine if the holes are of any benefit but even then it will be influenced by riding style, oil changes etc.
It is interesting that although the hole could be a weakness 'little grooves in the upper thrust faces' seem to be a good idea. So the holes themselves may not be necessary but the effect they had was considered so resulting in 'little grooves'.
Be careful making little grooves as they may weaken your con rod.
I remember stupidly fitting an oil pressure gauge on an A10 with a timing side bush. When cold I could get nearly 40psi with several swings on the kick start. Isn't flow is more important than pressure anyway?
After all the oil pressure warning light goes out at about 7psi.
Dave.
Hi,
QuoteIsn't flow is more important than pressure anyway?
I'm not convinced flow is more important than pressure on the A65 big end journal, it may be worth having a look at 'fluid bearing' principles. The rule of thumb is, most engines should be about 10 psi per every 1000 rpm, peaking around 55-65 psi.
Best wishes...
To a large extent the pressure is a measure of the resistance to the flow generated by the pump. Too much resistance and there is reduced flow, especially if the pump is a bit tired and cannot keep a good flow against the resistance The cooling effect of the oil on the bearing surface is reduced, the oil may get too hot and become less protective. So there is a balance to be established but unless an oil pressure gauge is fitted there is no way of knowing what oil pressure is being maintained. We all look in to the oil tank to check to see if the oil is returning and therefore flowing and on an A65 the only thing to say if there is a problem with the oil pressure is the light which goes off/on at 7psi. A big advantage of the end feed conversion is that all the flow goes to the big ends.
There was an article in a MCN or another publication some years ago in which Triumph ran a twin with no or very low oil pressure for the equivalent of several thousands of miles. When the engine was stripped and examined there was no more wear than would have been expected for that mileage. Probably not an exact replication of those miles on the road but a good indicator that the flow was more significant than pressure.
I will try to find the article.
Also, I may fit a pressure gauge to my high mileage A65 to see what pressure it is running at.
Dave.
I agree with dave on the flow over pressure, you see some people using 60wt oils to get the pressure up in hot climates but your limiting how much fresh oil can flow and not only lubricate but also cool the bearings (shells).
Another thing to think of is the 7psi light switch, it's use is to tell you if the ignition is on or not, if there's no oil in the tank and anything before the switch then it's helpful there too but should your shells start melting because of not enough oil or a blockage causing back pressure (which wouldn't switch the light on) then as the shells start breaking up and the aluminium coating starts to mush it will block the journals, any oil there would cause more pressure but no flow to the journal.
Another use for the oil light is to tell you when your shiny stainless oil pressure release valve has stuck open ;)
Hi Dave,
That answers the question, are holes in the con rod important? I guess with holes the oil pressure will fall and the flow will increase, two holes even better.
If you are fitting a gauge this might be worth a read. If you get the pressure right the designed engine tolerances will allow the correct flow, I might be the only one but I will be keeping my bike's pressure up:
Best wishes...
Hi,
I think all I will be doing is fitting the oil pressure gauge. In fact I did this today and bearing in mind that this engine has done over 100,000 miles without the bottom end being disturbed, the pressure came up to about 40psi just on the kickstart and once running it topped out at about 55psi as the release valve operated. I did not get the oil up to full running temperature and it was fresh oil but I did keep it running with a bit of revving for about 10 mins. and the pressure at tick over was still about 40psi. If I get a chance I will try to go out for a run next week and see what happens.
With this mileage the big ends must be well run in and allowing a lot of flow. One day I will strip this engine down to see what it is like inside but I reckon it is good for a few more miles yet.
Dave.
Hi,
I have gauges on my bikes and so does my son. I too checked the pressure not the other tests outlined on that sheet, never had the need. I posted it as it is the only reference I have to oil specification and pressure. The specification in the workshop manual being 50 psi at 3000 rpm when warm, but 12 different oils are specified.
His oil pressure was in specification mine wasn't. Luckily we fitted gauges as the flow into the oil tank looked fine but 5 miles out, my oil pressure dropped considerably. I once thought it's the flow you want. But remembering 'fluid bearing' principles from my apprenticeship days dismissed it. I fitted a new SRM pump, the pressure went 15 to 30 psi. I fitted SRM PRV increasing to 35 psi. Changed the pressure gauge its now at 50 psi in all circumstances. I think a proportion of the oil, when hot, was passing the oil pump teeth and circulating in the pump, worn pump. I am happy the pressure is now to the designers' specification, on a newly built engine if the pressure is correct the flow must be correct. To me, if the pressure is low the flow could be low and there's an issue such as no oil, tank/sump filters blocked, badly worn oil pump etc. as outlined in the workshop manual. Or more importantly, the pressure is low because the main bush is worn, end feed conversion seals leaking etc.
As for the oil pressure switch my thinking is, it is set at 5-7 psi as at idle say 850 rpm the pressure could be a minimum of 8.5 psi (10 psi per 1000 rpm) no warning. On a worn engine, possibly of no oil, worn pump or filters blocked etc. then the pressure could be below the switch's set point giving a visual warning. I don't believe it's safe that an oil pump delivering pressure slightly above the switch set point say, 10 psi at 3000 + rpm is okay.
That's why I'm not convinced flow is more important than pressure, I am up to being persuaded otherwise though.
Just wait until that stainless Oprv Gauls and sticks on you. Checked 3 now on different bikes and each one was buggered.
Hi Allan,
Galling, I did hear of issues with the cheaper end of the market so bought into SRM. I tried to make the original OPRV work correctly but being sold the incorrect spring and not convinced the existing threads were sealing between the galleries, gave up. It would be interesting to compare failures of the original OPRV design against the SRM solution as the original had its failings.
To help I have a filter in the return line to give it every chance to continue working correctly and fitting the pressure gauge gives me immediate indication of any issues. I feel I can't do much more in the oil line to mitigate the risk.
You've had some bad luck with galling, out of interest how many bikes have you checked to find 3 with issues?
Best wishes...
I must admit that I am not an engineer but I think I have grasp of things and can understand principles when explained for the layman. So here is something that is quite interesting and I think I understand it.
"Oil Pressure Vs Flow
Optimal oil flow with the correct pressure ensures optimal cooling and lubrication.
Oil pressure is to be understood as the resistance in the engine which the oil overcomes to establish a certain flow rate.
The most important criterion for good oil lubrication is optimal oil flow and not oil pressure. Low oil pressure is not necessarily bad, in fact it can be beneficial to some extent. High oil pressure is not necessarily good, in fact it can be a cause of concern.
Oil pressure is not built by the oil pump, but by forcing oil through small passages. Small oil passages with high viscosity oil will have low oil flow rate, whereas large oil passages and low viscosity oil will have a higher flow rate.
A fast flow rate with lower oil pressure will result in minimal wear and optimal cooling. A low flow rate with high pressure will result in a less efficient lubrication and cooling and therefore more wear on the engine.
Too high an oil pressure can result in failure of seals and leaking of oil and should therefore be considered as an indication of poor flow.On a cold start the oil viscosity is high (oil is thick) and the oil pressure is therefore higher. As the engine warms up, the oil viscosity decreases (oil becomes thinner) and the flow rate therefore increases while the oil pressure drops and stabilises. When the oil pressure is stabilised, the oil flow is at its optimal rate and the wear on the engine is minimal.
Under ideal circumstances, the oil pressure should stabilise soon after startup. Any sudden larger increase or decrease should be investigated."
"How Fluid Film Bearings Work
Operating Principle
In a fluid film bearing, the stationary and rotating surfaces are separated by a thin film of lubricant, such as oil, air, water or process fluid. In a hydrodynamic fluid film bearing, the film pressure that separates the surfaces is created by the relative motion (rotation) of the surfaces as the lubricant is pulled into a converging geometry between the surfaces.
No contact of the surfaces takes place except during start-up and shutdown."
Are the big ends 'fluid film' or 'hydrodynamic film'? Also, it looks like the most vulnerable time is on startup especially after a time of inactivity.
Dave.
Hi Dave,
Interesting read and you haven't convinced me. Bearing in mind we are talking about a motorbike whose oil passages are as designed and matched to its pump. It's also fitted with an OPRV to stop high pressure. I guess that passage is for design engineers not operational engineers.
Here's my thinking:
The size of the oil pump is designed to supply the correct amount of oil to meet the engines needs. I believe the standard A65 is 1.4l/s (quite low compared to other marques), the SRM unit delivers more.
When the engine is new, the clearances are tight and the pressure is as specified and you will get fluid film. As filters block, OPRV galls, oil pump wears and the bearings wear, clearances increase and resistance to flow decreases dropping oil pressure.
When the pressure drops you get an idea something is wrong with the engine. With the increased clearances the pressure drops and the flow from the pump increases until it eventually reach its maximum delivery. You need indication something is wrong hence the need for a pressure switch or better still a gauge. A flow meter is not practical on the A65, also some people will think the engine is getting better when the flow increases because they believe flow is more important than pressure.
An example, if the main bush is worn the flow under pressure will find the least line of resistance along its edges, the pressure will drop and starve the big end journals. In this case the journals are subject to centrifugal forces so the oil is flung out you will get some hydrodynamic film before the bearings fail.
In the engine, generally flow stays the same but reduction or loss of pressure has many influences all of them likely to damage the engine.
Therefore I still believe pressure is more important than volume as volume is the constant, pressure is the variable. You need pressure to push the volume to the bearing.
Best wishes...
Hi,
Perhaps a bit of dead thread but I did put the oil pressure gauge on my high mileage A65 and I went out on a ride today.
Only about 40 miles and not the hottest of days but interesting non the less.
Starting pressure 55psi so quite good and almost certainly activating the OPRV when revs increased.
Once warmed holding steady 50psi but increasing with revs to OPRV activation
Little drop in pressure at slower speeds
Tick over pressure back home of 25psi
So on a really hot day and after a longer distance the pressures may be less but not bad for a bottom end that has done probably over 120,000 miles.
My conclusion is that I have the best of both flow and pressure for the big ends. Flow from the end feed and pressure from what must be good pump.
How long will it go on for? We will have to see as I do not intend to strip the bottom end unless something tells me I really need to.
Dave.
Hi Dave,
QuoteWe will have to see as I do not intend to strip the bottom end unless something tells me I really need to.
Like low pressure? ;) ;)
Regards Bess...
Perhaps low pressure but I am taking the pressure gauge off again. I wonder how many miles more?
Dave.
Really impressive readings for such a high mileage.
Definitely and I cannot claim any credit as I did not build the engine. The head has been overhauled and the carb replaced as the Amal concentric completely wore out. other than that all I have done is change the oil and filter and routine maintenance. I have replaced the primary chain once and the clutch friction plates once. I suspect that I will be replacing these items again quite soon.
Dave.