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Just getting into my first A65 engine and reviewing the Timing side bush. Read a lot of theories about why it fails and some of the exotic solutions SRM etc.Expensive and not always effective depending on who does it that day
The restriction of end play seems to be a common denominator in all of the solutions.The standard set up, even when built to the factory spec of .002" end float does not take into account that as soon as the engine warms up there will be .010 of side clearance on the crank.
Looked at a drawing of the A70 and BSA seem to have put a really large Thrust washer inboard of the mainshaft timing gear.This effectively controls end play of the shaft very effectively. Has any body tried this fix on an A65?

Hi Rob,
In my opinion problem with restriction of end play is not as common, as a problem with low oil pressure during idle.
Most of the owners of later machines I met complain about it, because they can see it as a blinking oil lamp.
This is why I see some variation of SRM solution necessary in this engine, to improve delivery of oil to the big ends and eliminate end play problem in one stroke.

For a few years I had been using a stock set up and it's holding well during these few thousand miles, but lower than necessary oil pressure is very visible if you observe your oil pressure light closely.
Specially in town, every spirited ride on the freeway cost you longer and longer periods of orange light being on during idling.

Hi Rob,

There's loads of info and opinions about this online and one of the factors is whether the engine has a ball or roller bearing on the drive side with a common view that the earlier engines, which had ball bearings suffer less from crankshaft float than the later roller bearing engines. This means that there is less chance of the oil feed holes from the casing being obscured.

I'm still pretty new to this but have had my early ('62 ball bearing) crank cases fitted with a new drive side bearing and then a new timing side bush which I've had line-bored with the ball bearing.

The idea here is that the important thing with these engines is the limited clearance between the bush and crankshaft journal which maintains oil pressure. If this wears then the pressure drops and you then enter a spiral where wear increases, pressure drops etc.

So I'm hoping that ensuring accurate alignment of the crank bearing and bush along with efficient oil filtering will keep mine running well for a while yet.

Cheers,
Bernie

Hi Adam,I think the end play when hot can start the shaft moving between the bearing faces causing wear and eventually loss of oil pressure.
Hi Bernie, the ball bearing on the drive side is tempting!
This motor is a 1969 Lightning unit pretty much the same as the original Firebird engine without the holes in the crankcase!

I definitely will use ball bearing in my next engine, and needle Timken bearing on the timing side ( already bought ).
No more problems with end play, and with amount of riding I do every year ball bearing will last for a long time.
Only tricky part will be re routing oil and making a quill in the inside timing cover.

I think that the problem on the A series is oil pressure. A well set up roller will work fine and the ball bearing does fine too. You don't have to monkey with setting the endplay with a ball bearing but it is a matter of choice. On oil pressure, I made some changes. I did not have a port (66 model) for a pressure light or a gauge so I removed the OPRV completely and pluggged the return line to the sump. I installed a Tee and one side returns to the tank where I installed a small ball type pressure relief that I bought commercially. On the other end of the Tee I mounted a gauge. This worked as expected except my new OPRV was too small to flow enough oil when cold and the pressure would be 75psi at idle. Once warmee up (about 15 -20 miniutes od riding) the motor registered about 45-50 psi cruising but would drop down to about 5 psi at idle. The culprit here is called hysteresis. To prove this I tested my OPRV with compressed air and while it opens exactly at 60 psi (the set point) but it does not completely close until the pressure is down to about 3-4 psi. The newer BSA OPRV's with a piston might behave a little better but I am not sure as I have no way to measure how it does. Anyway I put the small new OPRV back in the return line and installed a metering needle valve just before it. With the metering valve totally open the pressure was the same as before...45-50 psi cruising at around 3500 but at idle it returned to about 4-5 psi. I closed the needle completely so there was no bypass and I had about 25 psi at idle but it would peg my gauge at anything above idle speed. So I cracked the metering valve open to 1/2 turn and VIOLA I had about 17 psi at idle and the customary 45-50 psi cruising. So a little restriction in the retun line made a big difference. The only problem is I must open the needle valve on cold starts. As soon as the engine oil is warm I close it down to 1/2 turn open. It is good to go for the rest of my ride with excellent oil pressure throughout the range.
On the bush, I too align bored it very accurately and I have always had good oil pressure. I believe this is crucial to longevity on a BSA bottom end.

Mr Mike

Mr Mike, I totally forgot about your exercises with oil system.
Senior moment I think.

Bernie

The end play cutting off the oil flow from the feed holes in the TS bearing are complete BSA myth. If all the pieces used to control the end play are removed, you can not cut off the oil feed holes. You need .125"+ end play to get the oil feed cutoff. To get that much end play, the DS bearing has punched through the case and is in the primary. If that happens, oil feed is the least of your problems!

I agree with Trevor and Rich. I think that if you carefully put a BSA together it will run....and that is not a lot different than assembling other motors...they all need care in assembly. I do think that the quality of the BSA castings had fallen behind the times and I am certain that there engine assembly line left much to be desired. I think if their workers cared as much about these old bikes as we do, the outcome may have been different.

Mr Mike

Thanks for all of the input. Last BSA motor I did was my 63 RGS.
On that one I honed the -.010 main bearing up to standard and had the crank hard chromed and ground to give .0015" clearance.
Also shimmed the outer cup on the drive side to give .001" of end float.
That all seemed to work quite well so May follow the same idea on this one.
I also think some really low compression pistons would be a really good idea to give this motor a chance at a longer life.

I've worked in a few different places and the guys who would retire on the same ground floor grade they joined, always reckoned they knew what was being done wrong by "those idiots upstairs."

Ok- Back to my original question" has anybody tried to install the timing side location system that BSA put on the A70?
Does anybody know anything about?

If anybody could have an opinion it would be Rick Harriet ( Highway ).
I don't know why he is still silent about it.
I remember a conversation with him about this subject, but don't remember it well enough to repeat it.

Over the years I have seen all sorts of mangled, used abused A 65's running quite happily on the original set up.
If you intend it ride it all day every day at or above redline the the existing set up probably needs to be upgraded.
OTOH if you are keeping it to ride once or twice a month in standard trim & tune then the plain bush will serve you well provided that you change the oil very regularly.
With an electronic ignition, Podtronics & spin on oil filter fitted the bike will out last you provided you change the oil very regularly.

The biggest problem I have noticed with the OIF's seems to be bad ring flutter at very high revs which can blow a good portion of the only just sufficient oil strait out. The remaining oil gets way too hot & way too thin.
And by high revs I am talking in the 7000 + rpm range,
This will happen regardless of weather you have an end feed crank or not.

RSG Bob,
Only 202 A70's were made according to Classic Bike. The article does mention a change to the timing side bush and there is(was) a site that showed the parts. It was "Ole's web page" for A65's and A70's. The crank and rods were changed to make it a 750 but most of the rest is identical to the A65. I would think if you take it apart, the same kinds of changes that were made for the A65 could me adapted to the A70. If you need a new bush, they can always be made. I had one made for my A65 and fitted it right into the Vandervell sleeve with a small dowel pin to prevent turning. Worked great.
Mr Mike

Hi Rich, I agree about the myth(cutting off oil supply)! To clarify my comment and concern about excessive end play when hot.
I do believe that there will be about .010" of end play which when that starts rattling back and forward my cause premature wear in the bush and this will reduce oil pressure.
Also have found that the soft crankshaft is sometimes more worn than the bush.
This could be caused by hard particles embedding themselves in the bronze giving the shaft a good sandpapering.
Like everybody says,frequent oil change plus a filter.

Mi Mr Mike, the A70 diagram i looked at showed a large Thrust washer between crank timing gear and the crankcase face-Have not seen that on an A65.

RSGROB,
So is there no thrust washer on the inside between the crank cheek and the bush ala A65?. Is the washer on the outside just spacing out the gear or is it contolling left side movement. I don't understand?

Mr Mike

The thrust washer and shims are on the outside of the timing bush so you do not have to split the case to set the end float. Go to http://bsaocne.org/tech/svc_sheets/a70.html and see the parts list and diagram.

Made my own bush out of, as I recall, aluminum-bronze (a very tough self-lubricating alloy, also used in Vincent valve guides). Then had the crank hard-chromed and ground to size (necessary due to the toughness of the new bush material). Roller on the drive side, shimmed between case and outer race (no shims to wear or fall apart).
Fitted lower comp pistons (8:1 Venolias) and taller gearing.

Been riding her hard and putting 'er away wet for many years with no problems whatsoever.

Yes this is the set up I am talking about.I cannot tell from the diagram if the thrust washer is locked in place by the third oil pump retaining screw and the gear rotates againstit. If this is the case I wonder if the A70 Thrust washer has a bearing material applied to one face?

being a noob to bsa this topic is highly interesting to me as i have a basket case ready for love.i do not want to hijack a thread, but im trying to sort out the details of a lower end build. would it be correct in saying that the design of the a65 is atime tested design and the down-falls are the results of variables such as materials and workman-ship.will the bush-bearing system work fine with the right materials and with a skilled shop such a Rabers here in ca?would fitting a better oil pump help longevity? ive been riding triumphs for decades and never really worried about lower-end issues as these thanks

Hey Trevor, that is superb-just what I was looking for.
Only concern i have left is the fairly small bearing area on the thrust face and thin shims.
I think this solution was BSA's final kick at the can in terms of making the plain bush arrangement work.
Looks a lot less costly and complex compared to the SRM solution and easily transferred to an A65 motor.
Trvor is the end of Plain bush level with the recess or slightly set back?

Hey Trevor, could you provide depth and diameter of the recess?Many thanks
Rob

duster - you need to give the year. Early oil pumps were alloy, the last was iron. Some of the improvements can be applied to early engines.
The outboard thrust washer appears to run against the shims which run against the bare case. This does not look to be as robust as the original arrangement where the bronze faced thrust washer is held in the case and the crank runs against it. These engines were built for flat track racing so longevity was probably not a factor.