Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A65 timing side mods

Hi Rich, This is a 1969 lightning bottom end to replace the blown up original firebird unit.
I did NOT blow it up, just bought the pieces and want to build as good a motor as I can to get this on the road again.
Great information from most people, Much appreciated.
Rob

If it was my engine being rebuilt I would definitely try to ensure it didnt go bang after a few years. Looking at the history of the A65 bottom end design, we can see that BSA have made varyious attempts at controling crank end float including using a ball bearing on the drive side, a roller bearing with a shim pack on the drive side and finally an attempt to use shims on the outer timing side case. IM led to believe that the devimead TS roller conversion was based on advise from the BSA race shop.

One can only conclude that something wasnt right with the original design otherwise why would BSA continually tinker with it?

In the end, I suppose what you end up doing depends on how much cash you have and how hard you ride. There certainly seem to be some good options available and the best advise I can give is use an oil filter, decent oil and change frequently.

it wouldnt have taken much for bsa to cast the cases to take a bearing, and rob iv done over a 100 a65 engines mainly standard some end fed some with 3 peice roller bearings and extra bearings on the alternator,if you want advise then unless your going to ride it like you stole it leave it standard,what do you think is wrong with standard ?head in sand again

I can't say whether the main journal is undersized. I looked up the calculations in the machinery handbook and there are too many unknown variables for me. BSA had well schooled engineers and would know how to size a bearing. The design for oiling this TS main bearing in not unlikee most automotive engines except they feed from a main gallery to the main bearings and from there they feed one or two rods...just like BSA. I think and I've said this before that crank bore misalignment greater that a couple tenths will eventually wear out the bush, and oil pressure suffers causing failure. That's the problem in my mind.

RSGROB If you are gonna hot rod this motor I woulds see if I could control endplay using the A70 outside approach with an A65 thrust washer on the inside. if that doesn't work out you can use the lipped roller to limit left side movement as in the roller bearing A65's. If you are gonna just plod along like me, but a ball in the primary side and throw all those thrust washers away.

Mr Mike

How to cure such problems as I am facing same here

The drive side roller was to improve the life. The ball works, just does not last as long on a high specification engine.
The high gear on the five speed gearbox uses the rollers for controlling the high gear end float. There are roller bearings that have a separate thrust collar to make the rollers guide the shaft axially. I am not sure these are available in inch dimension. The closest metric is a HJ306 (30 x 72 x 19mm) 1.1811" x 2.8346" x 0.7480". You could easily modify the case/crank to take this bearing and control the end float that way.
I put the Machinery Handbook journal bearing calculations into a spread sheet. Basically what I found is the pump is too small for high RPM and load. At 7500 RPM, 55HP, 180F, SAE40, 50PSI oil, the main bearing with 0.002" clearance uses 0.6342 in^3/sec of the pump's 1.899 in^3/sec (ideal) output. At 0.0035" clearance the main is using 1.881 in^3/sec and there is still the two rods to feed. So what happens is the oil pressure drops from the assumed 50PSI. The minimum film thickness is 0.000107" which is almost the minimum recommended. This is also why you need a filter. That is not much room for dirt to get through without scoring the bearing.
I need to invert the calculations to solve for oil pressure given the oil pump's output.

BSA HOLY GRAIL: So what we really need is a bigger pump like one that is in the Honda's where there is a 5 lobe outer and a 4 lobe inner that both rotate at the same time - more capacity. There is a name for this kind of pump....

Ah HA here it is. Would somebody throw away the gears in our oil pumps and put in two of these TRICHOID ROTORS (and a 450 watt alternator please!) I bet you could still use the shape and outer dimensions of the original pump!



Then I could run 10W40 year round and the motor would be easier to kick in the dead of winter and I could pressure feed the top end.

Thank you!

Do you mean one like this?

This uses the gearotors from the Suzuki 250 dirt bike and retains the original drive spindle. One problem is the spindle does not quite align with the tachometer drive. The drive axis of a gearotor is closer to the centre of the outer rotor than with gears. There is not much room under the timing cover or between the pump studs for a larger pump or moving it elsewhere. I do not have a set of the 450 gearotors to see if they would fit.
Nothing wrong with gear pumps. Porsche still uses them on the 911 and derivatives. It is just the A65 pump is a little small.
I believe it is possible to mount a three phase generator from one of the Japanese bikes in place of the Lucas. I put one in the triple with just a new mount.

YES YES YES!

I don't see why we couldn't modify the inner timing cover to get some more room. As far as mods go that would be pretty simple. Could you not make a new worm gear on the crankshaft or change the angle of the drive shaft to compensate for the different axis of the new oil pump?

How do we get this built?

Most of us don't have the capability to modify cases and the days when there were shops on evey corner that could do this work are for the most part gone. I have to do what I can do myself. For those that have the capability...go for it. For those that don't, the ball bearing on the PS was used in the early A65's and in the A7/10's and while it has a lot less radial capacity than a roller of equal size it'll do fine if you're not 'riding it like you stole it". What failed most often on these bikes was rod bearings and cylinder siezures and that was a lube issue not the radial capacity of the ball. OTOH if you are running the roads at high speed like Semper, go ahead and beef things up what ever way you can.

Mr Mike

Great idea for improvement of the oil pump. I wonder why SRM, or somebody hasn't used this for their high-capacity pumps. As much as the thing costs, seems like it wouldn't cost much more to use this type of impeller. Maybe one could design a pump along the lines of a rotary engine?
BTW: The gear pumps on Porsche, VW, and triples reside within the case.
I can see where it would be a bit easier to adapt a different alternator to a triple. The alternator doesn't share space in the primary drive on triples. Maybe if I spent a day poking around at the local Jap-bike salvage yard I could dig up something.
All things considered, I'd be satisfied with a new Truxton with the shifter moved to the right side. Seems to be an easier mod.

Hi Mike, I believe all of the the later A10's had a roller main on the drive side, certainly the super rockets and the RGS did.
Not sure when BSA dropped the baal bearoing drive side.

The 1960 A7 Shooting Star I had when I was 18 (49 years ago) certainly had a roller drive side main bearing.
How do I know?--because it threw the drive side con rod and punched a neat hole in the drive side crankcase necessitating a complete rebuild.The crankcase was rewelded by a Lloyds certified welder in a local engineering works for the cost of a packet of 10 Woodbines (cigarettes)---which was the accepted currency in those days for any "foreigner" done in the factory.
Happy Days!

So, that's it, BSA figured we wouldn't complain as long as we could find some, "foreigner," to fix it for a pack of smokes.
No sense cutting into the stock dividends to do real R&D.

i dont know why you lot have bsas there obviously a dissapointment to you, go buy a Honda and put bsa badges on it.

No disappointment,Wak, after rebuilding the motor the bike gave me 9 years and many tens of thousands of miles of great service. It was my only transport for that time.And I was young then with only one throttle position--flat out.
BTW I came to UK a couple of years ago and bought a very similar 1960 A7 Shooting Star (polychromatic green color) and brought it back to US. Interestingly only a couple of hundred numbers different in engine number from the one I had all those years ago.
DavidP--just a slight correction--the Brit factory jargon at that time---a "foreigner" was not a person but a private job carried out in factory time by factory guys (and the management normally looked the other way as they did it too).

many thanks for all the good ideas.
in summary, it appears that a sugnificant number of folks seem to think the standard set up can be reliable if a a late oil pump is fitted and if correct diametral clearances are achieved,
Also if an oil filter is fitted.
All of this if you do not thrash the heck out of it.
I will look into the A70 system of controlling end float as BSA seemed to think it was a good idea
Once again many thanks for a thought provoking string.
Regards
Rob

Most people do not want to irreversibly modify their engines so modifying the timing cover is something to be avoided. There is little room to work with so major changes to the layout is also out. The speed of the pump can be changed by making a new worm but that is expensive. On the triple I was able to change the gear drive to a Virago chain drive to increase the pump speed with only adding a tensioner to an existing bolt.
I am not sure what the SRM pump cost is but these gerotors are about $25 each, retail. I am getting a set of RMZ450 gerotors to see if they fit in the space available. The 250 gerotor is still a little small in volume. I am trying to source off the shelf gerotors, custom pieces drive the cost way up. Parker Hannifin makes gerotors of a suitable diameter but they do not sell individual parts.
A Japanese three phase generator can be adapted to the twins. You have to turn it around and mount the stator to the primary cover.

I found a website with details of a DIY version of the timing side needle roller conversion Here .

I have no idea whether this works well or not but anyway food for thought......

RAGROB,
Sorry on the misinformation. Some one told me the A10's and A7's were ball bearing. Do those motors control float like the A65's. That was one of the reasons I put a ball in mine. So the only DS ball bearing was from 63-66 on the A65 models?

Mr Mike

If I remember correctly the A7/A10 used a two piece timing side bush---a steel outer with a bearing material "cast" onto it.
End float was achieved by shimming between the crank and the inside of the roller bearing inner face.
Been about 40 years since I rebuilt my A7SS but I think the above is correct.
Particularly on the A7 the standard timing side bush was perfectly satisfactory over many thousands of miles.
I believe the problems only started when BSA tried to wring more power out of the A65.
HTH

Tridentman,
I'm pretty certain the two-piece ts bushing was pinned together...

Disappointed? Well, it hasn't blown up yet.
However, if I had perused the vast knowledge and opinion offered by the folks on this fine forum before buying a BSA, I would have held out until I found another Triumph.

I can tell you I have screwed out two triumph,s yet the a65 has survived splendidly. Disappointed.....are you sad that your BSA hasn't blown disproving the theory that all a65 are hand grenades.
I don't think that the general opinion of people on the BSA forum are anti a65's, quite the opposite I would say.
Mark

Trevor,
So on a7/10's the shoulder of the bush was the thrust surface on the right side and the amout of float was controlled by a shim pack on the roller cup? I wouls like that better thatn that thrust washer jingling around in there.

Mr MIke