Author Topic: 1940 Real C12 a 350cc version of the C10  (Read 4585 times)

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Offline hampshirebiker

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #15 on: January 21, 2018, 10:10:56 am »
Point taken.
Postal - Liphook Hants - But just into West Sussex.

Offline Owen

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #16 on: January 27, 2018, 11:29:40 pm »
Ive been researching the original C12 and found a few of the engine parts were from the earlier B23 Delux and B29 models.
The decompressor assembly is the same as a M20.
« Last Edit: January 28, 2018, 08:40:49 am by Owen »
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline timsdad

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #17 on: January 28, 2018, 08:53:58 am »
It was Thorntons who I got those stainless valves from, Owen, and they've always been able to supply 'unobtainable' piston rings for me in the past for other rare bikes.

I've still got the original BSA box, complete with raffia packing, that my C12 big end came in from Draganfly. It just states that it's for the B23 model but the part number cross references to the C12 too. It's this cross-referencing that enabled me to get my C12 back on the road a few years ago and the 1940 parts book has all the models from that year listed in the columns and vague drawings of parts. The rest was just common sense and I didn't bother to keep anyone informed of what I discovered because there was no one else interested in the practicalities of this rare old model.

One thing that did elude me was details of the head steady. I just had to use initiative in making one up and sorting out where it mounted but I did stamp a part number on it. I presume, like the valve lifter and choke, it's not really needed and can be left off or disconnected.


Ray
Just a motorcyclist.

Offline timsdad

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #18 on: January 28, 2018, 09:03:43 am »
I think the valve lifter/decompressor for my 'user' C12 came out of the B23 engine I had under the bench and they mostly seem to be the same apart from the little inside lever.

The piston that was in it, when I bought it in the mid '70s, was a B31 piston and the Hepolite part number stamped on its flat top cross referenced, in an old catalogue at the time, to the correct piston for all the 350 BSA models still in use back then. The little valve pockets in the top threw me until I found this out.


Ray
Just a motorcyclist.

Offline Owen

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #19 on: January 28, 2018, 09:33:36 am »
The head steady is the same as a 1939 B23 Delux if you can find one to get the dimensions off.
JP Pistons list a C 12 piston as the same as B31

« Last Edit: January 28, 2018, 10:13:06 am by Owen »
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline Cosmikdebriis

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #20 on: January 28, 2018, 10:30:59 am »
When I was researching pistons to find one for my 1934 BSA R34 350 what became apparent is the piston dimensions for all* the 350's were the same in respect to bore and gudgeon pin diameter/height. There are/were some variance in compression height** as there were some high compression "sports" models but, on the whole they are interchangeable. Obviously SV engines would have a problem with a high compression piston but ordinary ones with valve pockets wouldn't really matter.
One last thing. Although some of the older pistons have the same dimensions, from memory, some have brass stoppers as opposed to circlips to retain the gudgeon pin and different oil holes.

* When I say all... All the ones I could find, so obviously there may be some specials.
** Compression height can be a contentious issue in itself as different people seem to incorporate (or not) any lumpy bits on top of the piston.
A bike on the road... Is worth two in the shed...

Offline Owen

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #21 on: January 28, 2018, 12:16:52 pm »
I found FWT Thoughton on Google who do vintage engine parts and will give them a bell to see if they have the valves.
Luckily the valve guides are the same as the C10.
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline chaterlea25

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #22 on: January 28, 2018, 01:21:30 pm »
Hi All,
When working on old Beeza's it pays to look "outside the box" as many parts from other models will work or
can be adapted easily
For instance, many years ago I cut down a B or M crank pinion to fit a 20's 250 round tank engine, I chopped of the oil pump drive, and the rest fitted straight on, likewise the magneto gear fitted without any modification

On my 350 L25ohv shortened B31 valve guides will fit the head, and modified Gold star inlet valves will work with later caps and collets (I'm missing the originals)
A C15T/B40 valve lifter assembly is virtually identical to the 20's part  ;D

On the other hand A friend is building a G14 V twin from a semi basket case
The V twin drive line parts seem to change from week to week :o as it seems that there were several different primary cases and the like, There seems to be at least 3 different sprocket positions on the clutch chain wheels
and several different length cush drive sleeves to go with them  >:(
The similarity to sloper parts also causes confusion

Does anyone know where a 1935 G14 gearbox case might be found?
The one with the project is pretty well fkd !  :(

John

Offline Owen

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #23 on: January 28, 2018, 02:32:16 pm »
It's all that sort of information we should be collecting to preserve the C series e.t.c.
I've been collecting what I can e.g. The Wipac & Lucas info I put on the site. Still more to collect. Now searching for Terry valve spring and valve catalogues.
Does anyone own a B23 Deluxe that they can give me the dimensions & pictures for the engine steady?
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline MilitaryRon

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #24 on: January 28, 2018, 04:05:36 pm »
As far as I can see, the B23 wasn't fitted with a head steady until the last year of production 1939. It looks like a piece of curved tube and looks to be mounted near or on the rear tank mount, bearing in mind that the coil is there.  Ron

Offline Owen

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #25 on: January 28, 2018, 04:42:07 pm »
Cheers Ron,

I wondered why there was no marks on the front down tube for the engine steady. Now I know it should be rear facing.

I've found out the RC12 clutch push rod is 0.200" longer than the standard push rod of 9" on the C10/11 of their time. So that answers a question of how much deeper the RC12 clutch chain wheel (65-3920) and clutch drive plate centre (65-3916) should be over the standard one. Now where can I get them from?
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline Cosmikdebriis

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #26 on: January 29, 2018, 10:24:05 am »
Was the B23 3 or 4 speed? 
I'm assuming the c12 was 3 speed?
A bike on the road... Is worth two in the shed...

Offline Owen

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #27 on: January 29, 2018, 08:53:32 pm »
B23 was 4 speed and yes the RC12 was 3 speed.

Now I'm trying to find out if the B29 clutch basket is the same size but different depth than a C 6 Spring clutch basket
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline MilitaryRon

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #28 on: January 29, 2018, 09:06:05 pm »
Might be best to PM Leon about these pre war parts. I still can't fathom out about the 1940 parts list, showing a 6 spring clutch for an M20. As far as I know, they were fitted with the Empire Star single spring clutch from at least 1939. ??? They adopted the Triumph 4 spring clutch after the war, but the AA still insisted on the single spring well after that.

I don't know if a B29 clutch will be any easier to find than a C12 clutch. Leon might well have some parts.  Ron

Offline Owen

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Re: 1940 Real C12 a 350cc version of the C10
« Reply #29 on: January 29, 2018, 10:28:49 pm »
Draganfly say the can convert a 42-3223 clutch chain wheel to make a standard C series 6 Spring version. I'll give them a call to see how they do it. They might be able to get one made 0.200" deeper.
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc