Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Timimg side bearing A10 - how many miles?

Just wondering if somebody has the experience. How many miles will it hold? I had the engine overhauled with original specs, new solid bronze bush on the timing side, align bored, SRM oil pressure release valve. Modified oil pump (middle block steel). Since then 10'600 miles, runs well. Frequent oil changes (Valvoline VR1 20W-50). I wonder how I could notice a drop in oil pressure, coming from clearance issues on the timing side...

Not sure on A7/10 but on 66 A65 I tapped a 1/8 NPT pipe thread in the cap and screwed in a gauge. Later I put the gauge up by the speedo. I think the key to longevity is the "Align bore". Lots of people just ream the bush on itself and the slightest misalignment will shorten the life considerably.

Mr Mike

Thanks for the tip. Instead of having it fix on the bike, I could think about a measurement from time to time...kind of service plug on it to remove for checking the pressure.
I agree with the align boring, the shop who did it told me this is crucial.

First I would change the oil from mineral to fully synthetic. I have been used Mobil 1 since it came to market in my Gold Star. Ok, Gold Star is different engine, but I have been overhauled many A7/10, A65 and Triumph engines and suggested to use fully synthetic oils after overhauling. All those engines have been working very well for many miles.

I have hardchromed the crankshafts at the bearing site and grinded it. That will give many more miles. Align boring is MUST!

OK, this may start the never ending discussion about mineral vs synthetic oils. I have not heard any points, why mineral is better than synthetic!

Hi Opo,
Does the bike have an oil filter in the return line?
10,600 miles ? its hardly run in. The bush should last many times that mileage, Even if the engine has a proper air filter I would expect the top end to wear before the crank
It is easy to check the bush for wear, remove the timing cover, rig up a DTI on the crank end, use a screw drive to try and lift the crank end
The DTI movement will tell you how things are

John

John, thank you for your comments! "10,600 miles ? its hardly run in." this sounds good to me . Hardly doing 1500 miles per year, I might not need to worry for this too much. I am not running a oil filter, all original setup.

About checking: What is a DTI?

Opo, I am aware that synthetic oil is able to take more load and lasts longer, but the 20W-50 keeps older engines low on leaks. A dilemma! I have quite some stock of this oil, using it also in a Chevy Small Block, here the additional issue is the "zink" content to protect the cam. But yes...an endless discussion

If the build was done properly the only thing that will wear the bush
quickly is dirt in the oil. For the sake of a few dollars and a couple of hours
fit a return filter, any bush main bearing engine should have one.

It's a Dial Test Indicator.

Bushes and shell bearing rely on the oil film thickness, every time its zero the journal and bearing touch and wear occurs. The better the bearing material the longer it will last but fully synthetic oils have the best properties to maintain the oil film thickness over zero. No touching equals no wear, I use 10/60 fully synthetic, thin when cold to get to the bearings quickly on start up and thicker than 50W when warm for good oil film thickness when under load.

Without long term testing in actual engines in similar conditions there is no evidence that any synthetic is better than VR1 conventional oil in engines designed 70 years ago...

I went by my sump magnet, this was always furred up when using dino oil at oil change time, went to the 10/60w and the furring stopped.

If thats what you beleive then keep using the oil you prefer to use. Those of us that want to use semi/fully sythetic oils will also do so and with good reason. I use 20/50 ester based Semi-Synthetic (Fuchs Comp 4).

My race bikes have VR1 full synthetic in them...

Ok, understood. I have one, so I'll try it next time when I check the timing side condition (oil pump, worm drive, dynamo chain..)

A film of oil between the journal and the bearing, a properly clearanced bearing, align bored are all required. Decent oil pressure also helps.

Mr Mike

The factory recommendation for bottom end rebuilds was 30,000 miles
And that was on 1950's oil without external oil filters
I know of an A65 ( basically the same bottom end ) that did 80,000 miles on a dud bearing that would not hold pressure when hot simply by the owner doing oil chages after every weekend of riding.
The oil he took out was always fairly clean looking & when he had accumulated enough "used oil" then that got used to change the oil in his F100 truck .

There is no such thing as changing the oil in an A10 too often and cheap oil changed very regularly will be better than expensive oil left in there for too long, which is the problem with most synthetic users .

A cheap multigrade mineral oil will fail much sooner under sheer stress than a multigrade synthetic oil. So despite his oil being clean at the end of the week, if he was using a multigrade 20-50, he might as well put 20wt in the Truck, also the wear metals and other contaminats were probably screwing up his truck motor too, 2 pts of oil each week soon adds up in cost, he would have been much better just fixing the bike.

Allan ,
This was in the 70's & 80's
No synthetic oils back then outside avaition
Just posted as an example about how regular oil changes can drastically extend the life of a bottom end.
As for Rhetts mtives well you would have to ask him but he died some time ago
He sold the spare bike he bought to ride while he fixed the old one when he worked out the regular oil changes were preventing a drastic failure .

I just clocked over 28500 miles on my old crate (a65) that
has the original bottom end and runs on cheap multigrade
which is changed every 5k or so along with the filter.
The oil light still goes out on the kicker and it still revs to 7k
with no 'orrible noises.
The amount of dosh some blokes spend on oil for these old
crates could buy them a new engine every 5000 miles eh?