Motor Identification

[Ron B]

I have two engines
CA10 SR 556  is a 1959 Spitfire engine
DA10 R 1308 is a 1960 A10RR engine
What is the difference between the two  I know what the Spitfire engine is but know nothing about a A10RR.  Also is there scrambler gearbox and what it that noted as?  Thanks to whoever can explain the difference.

[bikerbob]

Hi there
According to Roy Bacon's book DA10R is a Super Rocket engine.  A10RR is a A10 Road Rocket 1954-57 this preceeded the Super Rocket 1958-63.  DA10 R 1308 would be a 1960 Super Rocket.  

[Topdad]

Good morning Ron, From pure memory I always thought CA10 numbers denoted the small crank engines but it will be interesting to hear from poeple who know this stuff backwards ,over to the experts, regards BobH.

[bikerbob]

Hi there
As regards the large Journal crankshafts they originally first came in  1954 for the Road Rocket  with engine numbers beginning CA10R and were first used for all A10's in 1958 and also those years coincided with the introduction of the thick flange barrels, this info comes from Roy Bacon's book on the Bsa Twins.

[Rusty nuts]

Hi

A scrambles gearbox will be stamped STB (mine is, but see also quote below I turned up while researching) here are the ratios:

                          4        3         2        1
Mainshaft           25      22       19      16
Layshaft             18      21       24      27

"These bikes were also referred to (in UK BSAOC maintained factory dispatch records) as Rocket Gold Star Scramblers. According to one source, the gearbox should be stamped "STB" on these models according whereas the West Coast Catalina Gold Stars that same year were stamped "STBT". But another source indicates it should have an stbt or arrt gearbox. Brett's gearbox has no stamping. Mine is stamped "STB" and Lee's is stamped "ARRT". Peter's was stamped ASCT.

Frame Numbers on these models should be GA10 just like the RGS although apparently some had GA10A stamped on the frames. Eng No. should be DA10R or DA10SR (it can be either). Frames did not have any pillion loops, although Lee (mentioned previously) owns a '63 RGS Scrambler with a full clubmans trim frame!! Per a page in the the UK BSAOC Star magazine, 272 Goldstar Spitfire Scramblers were made, and per another source all went either to Hap Alzina, or Nutley, NJ. There much the same as a "Normal Spitfire" except for the Four lug frame, usually low Goldie Scrambles 'Bars, Red fuel Tank, single sided Goldstar brakes, rubber fork gaitors, single seat, clamp-on foot pegs. Note: Four lug frame means that on the front down tubes there are 4 cast motor mounts, two top and two bottom, unlike just two top ones that all the other A&B series bikes had (including Spitfire Scramblers up to '62); the bottom motor mounts were welded on bits of tube."

HTH
Rusty

[trevinoz]

Sorry Rusty,
                      The STB box is not a scrambles box but rather one that has an extremely low gear which seems to have been an American market road box.
Usually marked STB2 or STD2.
Scrambles boxes are SC, ASCT, from memory.

 Trev.

[Rocket Racer]

Hi there
As regards the large Journal crankshafts they originally first came in  1954 for the Road Rocket  with engine numbers beginning CA10R and were first used for all A10's in 1958 and also those years coincided with the introduction of the thick flange barrels, this info comes from Roy Bacon's book on the Bsa Twins.

Sorry, but large journal cranks didnt come in on the early road rockets, only thick flange barrels did.
The 54 55 road rockets are small jnl, my understanding is that all or some of the 56/57 road rockets had the transitional large journal crank which is different to the 58 on crank. - All A10 engines from 58 used the common later big jnl crank
The '54/55 road rockets were also had twin port heads but I dont know if that was universal or not.



Pic included of transitional 56/57 road rocket crank with the later post 58 standardised big jnl type on the left. Note the transitional large jnl on the right is very heavy in the centre section (weighs a ton) but pulls like a train

[Rusty nuts]

                      The STB box is not a scrambles box but rather one that has an extremely low gear which seems to have been an American market road box.
Usually marked STB2 or STD2.
Scrambles boxes are SC, ASCT, from memory.

Well it's my understanding that it is a scrambles box albeit a US one! UK boxes were stamped SC or SC.T
It certainly came off a Spitfire Scrambler along with a large part of the Californian desert! & am told by the guys who race them here in the UK that's what it is.
The ratios are correct for a Scrambles box http://victorylibrary.com/graphics/A10-ratio-chart.jpg

Here is the link to the article quoted http://bsa.hailwood.com/goldstarspitfirescrambler.html

And here's a link to another forums article with contribution from our very own Snowbeard & some bloke in Australia called Trevor!

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=249432

Now, off to my garage where a single middle aged Italian all in red is awaiting my attentions!

Rusty

[bikerbob]

Hi there
As I said I am quoting from Roy Bacon's book on the BSA Twins and he quotes the same part numbers for the Road Rocket crank and the later 1958 onwards A10's 67-1216 as I have never owned a Road Rocket I will take your word for it sorry if I mislead anyone.

[Rocket Racer]

Hi there
As I said I am quoting from Roy Bacon's book on the BSA Twins and he quotes the same part numbers for the Road Rocket crank and the later 1958 onwards A10's 67-1216 as I have never owned a Road Rocket I will take your word for it sorry if I mislead anyone.

Bob,no need to apologise, nobody knows everything and theres a lot of misinformation out there. Even RB makes errors and omissions particularly when it comes to American market models.
According to a reputable UK magazine (classic racer) my A10 race bike is quoted as being bored and stroked to 750cc, but no one asked me and it was simply a typo in the race programme, which then got taken out of context!
Its important we do acknowledge some of what we think are facts are merely opinions and we dont know everything. The more I find out, the more I realise there's a lot more I don't know...
But hey this forum throws up some interesting stuff for an A10 addict. Keep it coming.

[trevinoz]

RR,
          I don't think that the thick flange barrel was available until 1956 along with the heavy billet crank.

 Trev.

[Rocket Racer]

Trev,
 you may be right, but that's not what I've read or my (limited) experience. Never any guarantees that the parts lists cover everything the factory issued. But my belief (however flawed) is that the 55 road rockets were small jnl/thick flange. This view originated from obtaining a low mileage 55 motor with a std crank and on genuine bsa +20 8:1, with the correct cam that had this configuration...then reading up the various imperfect tomes that don't all agree or at least are unclear but some outline this combination for all road rockets.
I think its also quite feasible that the road rockets were not all consistently built relative to the parts books and that servicing in the day makes this difficult to substantiate, particularly as most writers (aka Roy Bacon and Mick Walker) both write from the UK market perspective that didn't receive the early road rockets.
My suspicion is that the road rocket highlighted the need for stronger parts, how early they were fitted is a moot point...
I have seen an A7 motor with special daytona markings (circa '55) that has a thick flange and hasnt been sleeved down according to the owner... but having not pulled it down or checked casting numbers could be a complete mash up...but it looked legit having the proper twin port head and some other rare parts on it.
I'll try and shut up and hide my ignorance...

[bikerbob]

Hi there.
I don't think we should get to hung up about when a particular model had certain parts fitted when you realise how BSA operated. It is my understanding that BSA model years did not run from January to December but coincided with the factory annual holidays which were at the end of July so model years ran from the beginning of August one year until the end of July the following year. So any changes to models would begin in August but they would also use up any old stock first so the early ones off the production lines could have mixture of new and old parts. This has happened to me my A65 which is a 1963 model with all the 1963 changes actually left the factory in October 1962 and dispatched to a dealer in Bristol. Also I have seen a genuine and totally original 1956 BSA B31 that should have had the ariel hubs fitted but still had the older half width hubs fitted.

[Seabee]

For what it's worth, my 57 Road Rocket has thin flange barrels.  I haven't been into the bottom end to check journal sizes.  The engine ran so good when I bought it that I am not going to fix what isn't broke!