A10, engine parts interchangeability

[Zonker]

Hello all, new to the forum here(it looks brilliant) I am thinking of beginning to piece together an A10 motor for a bobber. I have quite extensive experience on building motorcycle engines from the piles of parts but wanted to find out about year to year interchangeability on the A10 and A7 before starting to gather parts. I see quite a few parts on ebay for them but want to avoid having to buy parts repeatedly hoping to come up with a working combination. Is there anyone here that can either school me on what will fit with what or point me to a site thate will tell me? I read back 20 of 45 pages hoping to find such a thing but my eyes are starting to bother me so I decided to just ask.

I do home metal casting and have built myself a cnc mill/carver and am thinking of trying to cast quite a few parts as I collect them as well.

Thank you in advance for any help.

[Desburnett]

Hi welcome to the forum.

Many of the cycle parts are interchangeable year on year including ancillaries such as dynamo , magneto.
Chain guards, mud guards..... The engines of course have the biggest differences in Crank cases, Crank, cylinders, pistons and  heads which are not individually interchangeable except for the rocker box unit.
You will find the external cases are interchangeable as well as the clutch unit.

Des

[Zonker]

Des thank you. So it would be safe to start collecting the clutch and housing, rocker box, timing/cam cover/housing? Then when it comes to cranks housing cylinders and heads those need to be more carefully matched is this correct?

[dpaddock]

Welcome, Zonker.

Go to the following web site and get a Spares List for your BSA project:

www.britbike.com/forums/ubbthreads.php?ubb

David

[muskrat]

G'day Zonker, motor wise most of the parts are interchangeable A10 to A10, A7 to A7 bar the early long stroke. The cases for a '54 swing arm are the same as a '63 A10 and A7 the same. The only difference between A7 and A10 is the head + valves,barrels,pistons,rods,crank and push rods.
An alloy head will fit where a cast iron was (different bolts), thick flange barrels replace thin flange (longer studs required), large journal crank and rods replace small journal. Have fun.
Cheers

[trevinoz]

Muskrat,
                  I'm going to be a smartarse and say that the '54 cases and the '63 cases are not the same.
Definitely interchangeable but slightly different.
Trev.

[Zonker]

Muskrat thank you that helps alot.
Trevinoz for my purposes it was agood answer for someone interested in Concourse type building it would not be the best but for someone who is leaning more toward custom/ rat type stuff it helped alot.

[muskrat]

No worries Zonker, I don't mind mixed matches. Being of limited budget i tend to make things fit. I do have great admiration for the Concourse builders and love to see a bolt perfect restoration.
I have used Tri T150 pistons in the A7 with shortened A10 rods and through bolted the head to the cases. Thats what I love about these motors, mix'n match.
Cheers

[terryk]

Hi Zonker, the first thing you need to know or work out is what frame you have or intend on using. In pre 1954 they had plunger and rigid frames and the crank cases are different to the later swinging arm frame. The pre 54 had the gearbox boltup to the crankcases. When swingingarm frames came out in 54 gearboxes were separate to the crankcases. Plunger framed bikes had different clutch and primary setup. They also had the inner primary case as a part of the drive sidecrank crankcase and the outer primary case is shorter than the later swingarm models. So if you havent got a frame yet work that out first because parts differ between plunger and swingarms. Many internals are the same so you can use them but dont start collecting things until you know this. cheers Terry

[Zonker]

TerryK without a doubt good advice and I appreciate it but what I should have said in my original post is I will be building the frame myself. Having built the frames for 5 of the bikes I've built(and chrome plated two of them)I've come to the conclusion that it saves money and alot of effort, plus fits me alot better(I'm 6'4 and look like a bear on a bicycle on a stock frame).

[terryk]

Ha thats funny Zonker. Well I guess you need to find a motor and gearbox and work around that so either will be fine. I think in your case swingarm stuff is the way to go and it opens up better options to hot the motor up. Have fun let us know how you are getting along with it. Have you seen the DVDs Britown etc.

[Zonker]

No but I will certainly hunt for them. Thanks and will look for swingarm as much as possible. This is a project I would like to have finished before retiring and since I have 13 years to go for full teacher retirement its not a major rush. I've found that as much as I like riding the tinkering designing and building of a bike is roughly on the same level.

[muskrat]

Zonker, I like your grit. Make it as you want/need. Good to see you want an A7/10 as the heart of the project. Keep us posted, you can now post pictures.
Cheers

[Zonker]

Thanks Muskrat I may be hitting you up for advice and brain picking.

[A10Boy]

Zonker

Theres a great book [Oh yes it is], called "A7/A10 restoration" by a chap named Roy Bacon that will have most of the info you need to know. you could probably find one on eGay