Author Topic: A10 push rods question + identification of engine/parts  (Read 2561 times)

Offline octane

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Hi folks.

Wonder if any of you knowledgeable folks can help me identify my engine
as I don't know about it's past. The whole bike is a 'come together' of different BSA parts.

It's a pre-unit 650 and the number stamped on the block reads D 10 786
(There's no other letter than the 'D'. I seam to recall that there's supposed to be a letter more..no?)




...the head look like this. Valves are 35mm and 32mm.
Is it standard ?




..the pistons looks like this
and are stamped 71  5 .
Are those standard ?





My push rods look a bit dodgy:



My questions are:
...are the 'hardened' at the ends or can I just polish/reshape them
and push them back into action

...are they standard items?
They're made of some very light 'aluminium-looking' material.

Thanks for any advise you can possibly give!




BTW this is how the engine looked a few days ago:






..slowly coming together.
As of today:







Talk to ya' later!

Offline dpaddock

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The full engine crankcase number could be DA10, in which case it's from a 1958 Golden Flash.
However, if the alloy head is originally part of the engine, then the case number should be DA10 R and it's from a 1960 Super Rocket.
Steel tube pushrods are standard and very light (A7 push rods weigh 37.9 and 41.9 grams, respectively). Use a magnet to see if yours are aluminum. The ends look bad and the tubing looks mushroomed. I suggest you renew them.
Your valves and pistons appear to be standard for the SR.
David
'57 Spitfire


Offline a10gf

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 *ex* workbench just like mine (well, maybe not quite lol). Great pictures.

The pistons, they look like higher compression?

This is what SRM supplied as 7.5\1, (but they look more like 6.5\1):


A10 GF '53 My A10 website
"Success only gets you a ticket to a much more difficult task"

Offline octane

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The full engine crankcase number could be DA10, in which case it's from a 1958 Golden Flash.
However, if the alloy head is originally part of the engine, then the case number should be DA10 R and it's from a 1960 Super Rocket.
Steel tube pushrods are standard and very light (A7 push rods weigh 37.9 and 41.9 grams, respectively). Use a magnet to see if yours are aluminum. ...
Thanks Dp

The push rod do not react to a magnet.
A friend dropped by yesterday, and he was sure they're made of duraluminum / duraluminium.

They were probably in bad shape, from the bike running very (too) hard valve-springs (se below)
As the rods are  not hardened at the ends I polished them back into shape:




Several  attempt were made to make this bike go-faster:

It has the 'Spitfire' cam,
the valves had extremly strong springs and
 the valve spring collars were made of some sort of ligth-weight alloy
(both of which I've replaced with standard items,
 as the collars really looked like they could burst any minute.
They were slightly bend out of shape)

The pistons do look like some hi-comp. items.. don't they?

The bike has a few other non-standard go-faster upgrades (andshould I say brake-faster upgrades:
...Grimeca double-sided double-leading front brakes (four (4)  brake actuator-levers (terminology???)
and Ceriani front forks
...Triumph conical hub rear brakes
...Akront rims (the type with the high 'edges')
...Mikuni flat-slide carburettor

So I guess it was put together to go fast.

Offline octane

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..The pistons, they look like higher compression?..
Yes mine does have a deeper valve-cut-out
(donno if that's the right term. English is not my mother-tounge)

Thanks a10gf!

Online bsa-bill

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Piston look like 9.5 ( I've just put same in my Rocket Gold Flash ) road rocket and super rockets have different springs to Flash's but I would say they are lighter not heavier and they use different valve caps and base's so maybe you've got a mixture.
I'm impressed with your polishing results on the pushrods which I think are all some sort of alloy, lightness being a good thing in their case.
How did you polish them?
All the best - Bill
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline octane

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Thanks Bill, for your information.

How did you polish them?

I first took them to the bench-polish-wheel (that not the right term, but you'll understand)
keeping the rod in constant movement.

Then, to make sure the shape was right,
 I put an old 'rocker' in the wise,
put a bit of grinding paste into the 'cup'
and carefully made the 'boy-scout-wonna-make-a-fire-with-a-stick' movement:



and lastly, a bit of fine polish.

.

Online trevinoz

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A10GF, those pistons are 7.5:1 or thereabouts. 6.5:1 have a concave top.

Octane, have you had a look at the front of your cases for a date? Some were stamped on the front lugs. I magnified the picture of your drive side case inner view to try to determine approximate year of manufacture but the resolution was not good enough. From 1960 the casting had a slight boss around the main bearing. Previously it was flat.
   Trev.

Online bsa-bill

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sorry to disagree trevinoz    *sad2* yes the 6.5s are dished but the 7.5s I put in my Flash are flat, could be the start of a what piston to use thread though  *conf*

All the best - Bill
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline octane

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Octane, have you had a look at the front of your cases for a date? Some were stamped on the front lugs.
Donno if that's what you refere to, but I can see , what in the Haynes manual is refered to as,
'batch numbers'
They read 303/303




Quote
From 1960 the casting had a slight boss around the main bearing. Previously it was flat
I see. Yes mine has the 'slight boss'.
Here's a pic from when I heated the thing to get in the new bearing






Thanks Trev.

Online trevinoz

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Re: A10 push rods question + identification of engine/parts
« Reply #10 on: 18.07. 2008 06:09 »
Gents, attached are pictures of three pistons. 8.3:1,   7.25:1,   6.5:1.

 The new ones going into Octane's engine seem to be the same as the centre piston. The old ones look to be 8.3:1. I did have an old set of 8.75:1 pistons but I can't find them.
There are other configurations of A10 pistons, one type has a raised dome in the centre of the crown.
I used 10.5:1 pistons once, back in the 60's. The engine would not run on petrol from the service station so I had to use high octane fuel at 1.5 time the price. The pistons were only used for a short time as the barrel broke away at the flange.

Octane, it appears as though your cases are a matched set post 1959. The date stamp I mentioned was not always stamped on the cases
             Trev.

Offline octane

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Re: A10 push rods question + identification of engine/parts
« Reply #11 on: 18.07. 2008 08:24 »
Thanks Trev for your info!

One thing:
The new ones going into Octane's engine seem to be the same as the centre piston. The old ones look to be 8.3:1.
There are no "new ones" for me. I guess you looked at the new ones posted by 'a10gf' .


Thanks!