Author Topic: Plunger Crankcases  (Read 1073 times)

Offline Nourish

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Plunger Crankcases
« on: 26.11. 2013 07:50 »
Does anyone know what the differences are between the BA A7 and BA A10 Plunger Crankcases?
Cheers

Offline bikerbob

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Re: Plunger Crankcases
« Reply #1 on: 26.11. 2013 10:47 »
I have a parts list for 1954 onwards and the part number is the same for A7 and A10 so the only difference would be the number stamped on the case.

Online muskrat

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Re: Plunger Crankcases
« Reply #2 on: 26.11. 2013 12:24 »
That is correct, an A10 top end & crank (even the big fin) will go on/in A7 cases. My A7SS is now a A10SR and my '51 A7 plunger has the '57SS top end. The only easy way to tell an A7 from an A10 is the number of fins on the barrels (and how fast it gets to 100mph).
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'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Muskys Plunger A7

Offline terryk

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Re: Plunger Crankcases
« Reply #3 on: 26.11. 2013 13:13 »
Hi Nourish Im after a set of plunger BA7 cases. The engine number needs to be above BA7 2001 for 1954 I have the rest of the bike.
1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm

Offline Nourish

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Re: Plunger Crankcases
« Reply #4 on: 26.11. 2013 15:55 »
Thanks all for the replies.
Terrk - "The engine number needs to be above BA7 2001 for 1954" - Is that just the year you want or is there something different from 2001 onwards?
Briz tells me that the BA cases onwards have the oil feed to the cam.

Offline trevinoz

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Re: Plunger Crankcases
« Reply #5 on: 26.11. 2013 20:22 »
I'll tell you that I have several ZA10 cases with oil feed to the cam.
Trev.

Online Brian

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Re: Plunger Crankcases
« Reply #6 on: 26.11. 2013 20:43 »
The subject of the cam oil feed came up in another thread not so long ago and I have to say I am not quite sure what's going on.

I have pulled a lot of A10 motors apart starting from 1950 ones and I have never seen one that didnt have the oil feed. When they were realeased that was one of of the new features in all the advertising.

Online bsa-bill

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Re: Plunger Crankcases
« Reply #7 on: 26.11. 2013 21:18 »
am I right in thinking the oil feed to the cam only feeds oil to the cam when the PRV opens - begs the question how often this occurs or does the pump produce 60 lb/ft most of the time
 (I'm aware this should maybe in another board)
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 trevinoz

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Re: Plunger Crankcases
« Reply #8 on: 27.11. 2013 19:40 »
Bill,
        You are correct. The relief oil flows through a gallery from the valve to the cam trough. there is also a small drilling in the gallery which directs some oil onto the timing gears.
Probably the major difference in the BA cases is the provision of a crankshaft seal between the crankcase and the chaincase.

Trev.

Offline terryk

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Re: Plunger Crankcases
« Reply #9 on: 28.11. 2013 10:58 »
Yes Nourish I want the year 1954. I have the right frame number and original bits and the for the rest of the bike just not the correct engine numbers on the crank cases.
There was differences between 1953 and 54 A7 the fuel tank is one.
1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm