A65Con Rod

[Daia65]

Does anyone know, with the A65s, when they went to the peppered conrods , did they still have the oil drillings for the drive side bearings ?

[Mark Parker]

Unfortunately yes. They preferred to use two R/h rods for racing. The holes introduce a weakness and no benefit. MAP make excellent steel rods at a good price.

[DAVE BRADY]

Good morning,

The hole in the condor is an interesting topic.
The A10 had this hole in the drive side con rod and it had to be fitted facing towards the fly wheel.  The idea being that oil would squirt on to the fly wheel and be flung up the bore to ensure lubrication of the right hand cylinder. 
But consider that the oil under pressure wants to escape as soon as possible and will find the line of least resistance.

The first place to escape is the timing side bush but if it is a good fit it is still a restriction but some will escape as some oil needs to flow through this bearing .  Next there comes the timing side big end which again, if a good fit, offers resistance and some oil needs to escape to ensure a fresh supply and lube the right hand cylinder.  The drive side big end is last in line and again offers good resistance and needs a flow of oil through it.  Consider though that some flow and pressure has been lost at the timing side bush and then at the timing side big end so there is less of each at the drive side journal. 
So on the A10 the hole in the con rod served to reduce the resistance and encourage a more even sufficient flow of oil throughout the crank and ensure better lubrication of the cylinder.

The A65 engine is pretty much the same as A10 in terms of bush, big ends etc. so why did BSA not continue with the hole in the rod?  I believe that one of the issues with early A65s was one of seizure of the left side cylinder - someone will know more about this than I.   Somewhere around 1966 BSA started to put the hole in the lefthand con rod.  Prior to this the rods had the same part number and afterwards different ones.  I believe that this was done right to the end and that BSA though it a good idea, on road bikes at least, and at one stage the left hand rods had two holes in them.
Do non BSA A65 rods have holes?

Dave.

[JulianS]

I took these steel capped rods from an OIF which had been laid up for 34 years. No oil hole drilling but ends were at minus 40 and badly worn on both journals.

Note non bushed small ends.

Dont know if they were original factory fitments.

[DAVE BRADY]

Hi Julian,

Both of my A65s have such con rods with the steel caps.  They must have come in very late as the 1971 parts book shows the same part numbers as 1970,  71-1106 and 71-1105.  So the difference being the hole in the left hand rods.
Perhaps the engine had been apart and the left hand rod replaced with a right hand one.  It would be interesting to know if the left hand journal was more worn and if the left hand bore looked in worse condition than the other.
The later rods do not seem to be numbered so it is difficult to know if the are a pair or not.

Dave.

[JulianS]

Rough measurements showed the left journal about 1 thou down on the right, the right about 1 1/2 thou down on what it should be and both journals about 1/2 thou oval.

The left had a single circular score passing through the oil holes.

[DAVE BRADY]

Hi Julian,

So the right journal was 1.5 thou down and the left one 1 thou down on that.  Pretty knackered then.  The score mark seems to imply that a piece of something quite hard had come through with the oil and was carried around the journal. It probably broke up and exited through the relatively big gap of the worn big end.
Do you remember how much sludge was in the sludge trap?

Dave.

[Mark Parker]

Lucas changed the points cam and points bounce caused an extra spark if the gaps were a little big. All the British twins had problems the '66 Spitfires a rash of broken rods from overheating. They tried the hole, or holes, to fix that, my 1970 had a hole out both sides where it split.

The extra spark was the actual problem and new points and cam assembly fixed it. If you notice on the case they have an oil deflection plate between the r/h cylinder and Bush to prevent excess oiling of that bore.

The steel capped rods were BSA's best. Especially a pair of R/h rods without the weakening holes.

[JulianS]

Slugde trap almost fully blocked. Took some effort to pull the tube from the crank.

Bike on around 48000 miles from old MOTs so I am not convinced that it was cleaned out when the ends reground.

Bores were on  plus 20, wear appeared even on both but, presumably because of the layup in far from ideal conditions, there was a tide mark ring of corrosion in each bore but no significant wear lip.

The main bearing bush was minus 20 and showing wear.

This engine was in poor condition, water in gearbox ruined most of the pinions.

[DAVE BRADY]

Hi,

So an almost full sludge trap at about 48,000 miles or a bit before.  I think then it would be safe say that conversion to end feed and using a detergent oil and a filter can at least double the life of a bottom end.
I wonder how long an engine running the standard bush but with detergent oil and filter would go.

Interesting about the points bounce causing over heating.  I wonder why BSA kept drilling the hole as this was an extra operation and would not be without cost and BSA usually tried to cut costs if possible.  The change to the points seems to be at the same time as the holes appearing!

Dave.

[JulianS]

This 1966 service bulletin explains the points and overheating issue.

[Daia65]

thnaks for all your replies Dai