The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: mario medeiros on 15.10. 2013 00:24

Title: what did i buy? a 500 or 650?
Post by: mario medeiros on 15.10. 2013 00:24
Can't seem to get pics???how do i tell the differance between a a7 and a10 motor? it is a swingarm frame and the top of the tranny say std and the motor has a alloy head?is there a give away between the 2 motors?Thanks
Title: Re: what did i buy? a 500 or 650?
Post by: Brian on 15.10. 2013 01:39
Mario the engine number will tell you.

The number is stamped at the top of the crankcases on the left side, just under where the barrels bolt on. It will either have A10 or A7 stamped in along with some other numbers and letters. If you post the full engine and frame numbers we will be able to tell you what year your bike is.

The frame number is located on the left side frame rail just in front of the fuel tank.
Title: Re: what did i buy? a 500 or 650?
Post by: mario medeiros on 15.10. 2013 01:53
Problem is I can not read either number as someone at one time stamped over them? I was told to count the number of fins on the barrels to tell is a a7 7 fins and a a10 being 8 fins?
Title: Re: what did i buy? a 500 or 650?
Post by: a10gf on 15.10. 2013 02:27
Welcome to the forum, am hoping you will find all the help you may need.

Info about posting pictures: http://www.a7a10.net/forum/index.php?topic=427.0

An introduction post in 'Bikes, Pictures & Members' is always appreciated by all.
Title: Re: what did i buy? a 500 or 650?
Post by: Beezageezauk on 15.10. 2013 09:01
Hi Mario,

I also offer you a warm welcome to the forum.

You are correct.  The number of fins on the barrel will tell you if it is from a 500 or 650cc engine.  7 fins on an A7 and 8 on an A10.

Beezageezauk.
Title: Re: what did i buy? a 500 or 650?
Post by: bsa-bill on 15.10. 2013 09:20
And another welcome to the gang from NE England Mario
Does it run?
Title: Re: what did i buy? a 500 or 650?
Post by: muskrat on 15.10. 2013 12:44
G'day Mario,  *welcome*.
With the numbers obliterated it will be very hard to tell how she left the factory (not many are that way now anyway).
Give us an intro in Bikes, Pictures & Members section and tell us about yourself and the bike. A few pictures (a10gf's link will tell you how) will enable us to have a guess at what she is, or pretending to be. The A7's go quite well for a 500 and rev hard, the A10's have a bit more grunt, either will put a smile on your dial.
Cheers
Title: Re: what did i buy? a 500 or 650?
Post by: mario medeiros on 17.10. 2013 00:15
So i now know i have a 650 top end any way of knowing what bottom end i have besides the #'s on the case?
Title: Re: what did i buy? a 500 or 650?
Post by: muskrat on 17.10. 2013 11:21
G'day Mario.
Highly unlikely to have a 500 crank. Rods and stroke are shorter so she wouldn't have enough compression to blow out a candle *eek*.
But then again another forum member got one like that and it did run *dunno2*.
Cheers
Title: Re: what did i buy? a 500 or 650?
Post by: mario medeiros on 27.10. 2013 00:01
How is a bsa pre unit a10 titled? By the frame number or the motor number?Thanks
Title: Re: what did i buy? a 500 or 650?
Post by: muskrat on 27.10. 2013 00:17
G'day Mario, the engine # as all frames (bar the RGS) are stamped A7.
BUT an A7 crank, barrel, head, con rods, pistons and push rods can be put on A10 cases to make an A7.
To check what crank you have use a piece of wire down the plug hole to measure the stroke. 84mm for A10, 72.6mm for A7.
Cheers
Title: Re: what did i buy? a 500 or 650?
Post by: KiwiGF on 27.10. 2013 00:19
I recently found out the bsa despatch records are ordered by engine no so its hard for the vmcc uk who have the records to find out when a frame was despatched, its easy with engine numbef for them, but in terms of how registration is done it varies by country, in nz its a vin number attached to the frame, but years ago it was just frame no.
Title: Re: what did i buy? a 500 or 650?
Post by: Beezageezauk on 27.10. 2013 08:51
The UK BSA Owners' Club and the UK licensing authority (DVLA) both go by the frame numbers. 

In fact the BSAOC (UK) can issue a "Dating Certificate" that shows the model and colour of the bike, the actual date it left the factory and the dealership it went to.  These are inexpensive and are available to both members and non-members.

Beezageezauk.
Title: Re: what did i buy? a 500 or 650?
Post by: muskrat on 27.10. 2013 09:40
Same here, the VIN or frame # is the main identifier. So does that mean the only real A10's were RGS's *????*
Cheers
Title: Re: what did i buy? a 500 or 650?
Post by: RichardL on 27.10. 2013 12:59
Bzgk,

Wrote an email with a simple question to the BSAOC librarian about a week ago and still waiting a reply. Hmm?

Richard L.
Title: Re: what did i buy? a 500 or 650?
Post by: bsa-bill on 27.10. 2013 13:29
Don't know who the librarian is at the moment Richard but they are part time and schools are on holiday this week, might have a bearing
Title: Re: what did i buy? a 500 or 650?
Post by: KiwiGF on 27.10. 2013 19:24
So both the vmcc uk and bsaoc uk have the despatcb records?
Title: Re: what did i buy? a 500 or 650?
Post by: bsa-bill on 27.10. 2013 20:21
Quote
So both the vmcc uk and bsaoc uk have the despatcb records?
They used to be held at a dept in The British Museum IIRC then I think they went to VMCC, BSAOC could have copies or access to them not sure which
Title: Re: what did i buy? a 500 or 650?
Post by: mario medeiros on 28.10. 2013 22:45
removed the paint on my frame and it reads ea7 9146 so I think it is a 1957? But what is the model called?and it ia a 650? I hope.Thanks
Title: Re: what did i buy? a 500 or 650?
Post by: muskrat on 29.10. 2013 08:36
Yes Mario that would be a '57. If it's a 650 it could be a CA10-***** A10 iron head or CA10R-**** Road Rocket with an alloy head.
Does it have full width alloy hubs? Like these (disregard the scoop).
Cheers
Title: Re: what did i buy? a 500 or 650?
Post by: mario medeiros on 30.10. 2013 23:20
No neither of my rims look like yours,will try to get some pics.again my frame vin is ea7 9146?Thanks
Title: Re: what did i buy? a 500 or 650?
Post by: Brian on 30.10. 2013 23:45
Not the rims Mario, the hubs.

1956 and 1957 used the hubs the same as the ones in the picture Muskrat has posted, before and after those years they had different hubs.

The 1956 and 1957 are full width alloy hubs, commonly called Ariel hubs as BSA "borrowed" them from Ariel.

Just had a thought, Mario have a look underneath the motor just in front of where the sump plate bolts on, or maybe one lug further up the cases. You might find a date stamped in the cases. If there is a date it wont give you a exact date for the engine but it will give you a indication of when the cases where made.
Title: Re: what did i buy? a 500 or 650?
Post by: bikerboy on 04.11. 2013 03:06
The big problem with numbers is they may have no relevance whatsoever. Plenty of people have changed engines or used a7 cases instead of a10 and vice versa. The amount of fins on the barrels show they are a10. Again the alloy head will have a casting number on it because plenty of people have thrown a7 heads on a10s.