should I or shouldn't i ?

[DAVE BRADY]

Hi,

The big end journals still have quite a mirror affect but the 0.002" wear means a regrind is probably the best option.  If it had been a max of 0.0015 I would have got away with new shells.
So does anyone know of a good place to take my crank in North Lincs.?
I used to use a place in North Norfolk but that is perhaps a bit far to go.

Dave.

[DAVE BRADY]

Hi,

It is raining so I have been indoors thinking.  I know it can be dangerous but it just happens.
I have always loved the fact that my A65 would tick over very reliably at about 700rpm.  To some extent I saw this as testimony to me getting the settings right.  So a bit of kudos perhaps.
Thinking back to some previous posts were oil pressure was discussed it was suggested/stated that 10psi per 1000rpm was a good benchmark.  So taking this idea a bit further and linking it to my slow tick over, it would imply that at 700rpm the oil pressure would be 7psi.  This would fit in with the oil pressure switch being set to activate the warning light at 7psi as BSA seems to have intended it.  I would assume that the 7psi is to considered an absolute minimum for the oil pressure.   Also, at such low rpm, has the ability of the big ends to create an 'oil wedge' been compromised as the revs are slow and the pump is also performing at a minimum.
Could it be that over the years my slow steady tick over has contributed to some of the wear of the big end shells.
I think that I will use 900/1000 rpm and not worry about the extra fuel it will use.  Also, the engine will pick up better on opening the throttle and I will be reassured in the knowledge that the is a bit more oil and bit more pressure there to protect the bearing surfaces.

Dave.

[idie]

The oil pump would certainly work better at higher revs.

[EDDIE SIMPSON]

hi dave, the breakdown in oil viscosity at low speed and hot engine days was a reason for the oil cooler on tridents and rocket 3s. its stated in the t160 factory manual somewhere from memory i m sure. i dont know if the a65 oil pump is up to an oil cooler . of course cover it up in the winter.
years ago i owned a norton 650ss with one fitted by previous owner who swore by it for long distance motoring.
another direction is to have the crank nitrided. i had my t160 crank nitrided at p&m who said the standard crank journals are too soft. the process distorts the crank and the trident crank has to be staightened on a press afterwards. not sure if a twin would distort.
the oil cooler option would be a lot cheaper.

[DAVE BRADY]

Hi Eddie,

The pump can cope with an oil cooler as it does not present any restriction to the oil flow.
I know that Norman Hyde produced a thermostat for the 3s so it mist have been considered that they could be running too cool.  I know of a T160 rider who fitted one and the only time it opened was after riding up and down the Pyrenees on a very hot day.
The cooler will only cool the oil when the bike is moving and the hotter the air the higher the speed needed to have an affect and it is when stationary that I find that things get hot.  Perhaps an oil cooler with a thermostatic fan would work as on the cooling systems of modern bikes as even on summer days it could be possible to over cool the oil at higher speeds.  One advantage is that a bit more oil will be in the system.

I suspect that the high mileage is mostly responsible for the need to replace the shells and it is interesting to note that the one that has suffered the most is the upper drive side.  The upper shells must take more hammer as they take the combustion pressure and if there is an issue with oil delivery and or pressure it is the drive side that suffers most.

Although on the limit of clearance tolerance, the crank journals look good so I am leaning heavily towards the mileage of the bike and the resulting fatigue in the shells causing the issue and the weakest shell went first.

Dave.

[EDDIE SIMPSON]

hi dave, yes i also have a hyde thermostat somewhere in the back garden where i chucked it.
i think your partly wrong about the oil cooler not working at tick over as oil is still cooling off as its pumped round. i once fitted an oil pressure guage to my t160 as the red light used to flicker on in traffic and what i noticed is that oil pressure was greatly boosted when the airflow hits the oil cooler so will help maintaining viscosity  in stop start traffic conditions. speaking to srm who have a test rig recommend straight oils due to thinning oil when hot.

[DAVE BRADY]

Hi Eddie,

The increased oil capacity and surface area of the cooler and associated pipes will help but one with a fan would be even better.  Once moving the cooling will better/quicker with an oil cooler than without.   
I have always used 20/50 and never had a problem over a very high mileage.  I suspect that the fatigue/wear on the big ends is down to high mileage rather than the oil.

Dave.

[DAVE BRADY]

Hi,

I am always unsure about how to compare mono grade vs multi grade.  My understanding is that at a 20/50 is thinner than a straight 50 when cold so equivalent to a 20 and so circulates easier at startup getting the oil around the engine easier.  At working temperatures the 20/50 and the 50 have the same properties and viscosity and so circulate with the same thickness.
If this is so then why use a straight grade oil?

Dave.

[EDDIE SIMPSON]

hi dave,
i also use 20/50 on my bsa s with the commando oil filter but i have 2 bsa s without filters and use straight oils in those engines. i must say the b31 seems to like the mono oil and no leaks. my only worry with multigrades is the low viscosity at tick over when really hot. i m not convinced you get 50w then although it says it on the tin. just my view.
as you managed over 100,000 miles your oil and filter did its job. which oil make did you use / recommend dave?

[DAVE BRADY]

Hi Eddie,

When it was available in Asda I used Duckhams.  At the time it was always on offer but Asda stopped stocking it.  I ended up speaking to a chap who used to supply tractor oil for work and he recommended a commercial car fleet oil called Batoyle by Freedom Oils which was taken over by Fuchs, 20/50 full detergent oil.  As we were doing a lot of miles I bought a 200l drum and it lasted for quite a while and worked out quite a good deal.  I am now on the last 40l of a second one which has lasted longer due to doing less mileage and Covid restriction.
When I need some more oil I will have to see what is out there but perhaps not 200l this time. Fuchs still do a range of 20w/50 oils.
I think the thing is to probably avoid supermarket oils,  change the oil regularly and use a filter.  Generally, I did an oil change before and after a long trip.

Dave.

[Bess]

Hi Dave,
              Multigrade oils can be fine depending on their shear stability. They can shear down below the 20W/50 stated on the can in service, which could be below the original monograde requirement of SAE40 (summer). After the oil has sheared and its viscosity has lowered you might find you have flow but less pressure, usually seeing less pressure at tick over. If your oil pump is worn damaged oil will flow back from the discharge to the suction side of the pump at low revs.

When using multigrade and experience low pressure try SAE40 first. If the oil pressure is fine go back to multigrade, change the oil more frequently and use a better standard of multigrade. If the pressure is still low check the pump. PRV, engine etc.

I wouldn't use multigrade on worn engines, the polymers and additives will increase carbon deposits.

I wouldn't use multigrade on engines with roller bearings such as the B31 as the rollers speed up the sheer.

Best wishes...

[DAVE BRADY]

Hi Bess,

Thanks for the reply.  I agree re roller big ends.  As I have mentioned I do think that the drop in pressure was most certainly due to wear and fatigue with the heat of our ride back from Belgium being the final straw that dropped tick over pressure to below the 7psi that triggers the warning light.  In the image of the shells it can be seen how the fatigue had caused 'worm' channels and distorted the bearing surface. It has also been suggested to me that this could be caused by acidity in the oil but why now and why predominantly one shell?

Dave.

Just done a bit research about engine oil shelf life.  Most suggest about 5 years for an unopened container.  I am now thinking that as I have had my oil for a few more years than 5 that, not withstanding the mileage covered, that this may have been a contributory factor.

[Bess]

Hi Dave,
             I had a look at your shell images. To me it looks like surface fatigue, from the mileage you had from them its expected. I would say you did well, you have the PPM and fluids about right.

Best wishes...

[EDDIE SIMPSON]

all interesting information from bess.
duckhams oil was a lovely blue colour so looked like real oil. i havn t seen it about so much any more.
the old , long deleted esso 20/50 oil was a lovely colour and texture as well. i believe the green colour upset the greenies so it was banned in holland.
the fan cooling oil via an oil cooler is not such a bad idea as those fans are widespread and cheap and used for cooling electrics on trains, forklifts etc. only a live and neutral and could use a handlebar switch for hot days stuck in traffic.
not all roller bearing cranks need mono oil though. jap 4 s such as suzi 750s use 10/40 multigrade and will cruise at 70mph all day long. food for thought.

[DAVE BRADY]

Hi,

I have ordered the parts and arranged for the regrind so all is going to plan.  If any one is interested I may start a new post when I have every thing ready to go.

Dave