Author Topic: A10 compression ratio  (Read 837 times)

Offline melvyndalby

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A10 compression ratio
« on: 26.08. 2011 19:47 »
I recently aquired a BSA Rocket Goldstar (REP), it has +60 pistons in it,  can anyone tell me how I can find out the compression ratio,  thanks Mel

Online bsa-bill

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Re: A10 compression ratio
« Reply #1 on: 26.08. 2011 20:23 »
With possible exceptions, flat top 7.5:1 ,  raised portion and then flat top 8.5:1 ,  Domed top 9.?:1
Could differ depending on make I would think

All the best - Bill
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Online RichardL

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Re: A10 compression ratio
« Reply #2 on: 26.08. 2011 23:16 »
Really tall peaked top,  10:1 (oooh,  very scary,  batten down the hatches,  wear the brace on your rightright. knee).
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Online muskrat

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Re: A10 compression ratio
« Reply #3 on: 26.08. 2011 23:29 »
G'day Mel, welcome to the forum.
                                             Also look inside the piston for make or casting #'s then google.
 The other way is a bit messy, but the one I use, is to cc the combustion chamber. With the piston on TDC comp stroke lean bike over till the spark plug hole is vertical, then using a syringe accurately measure how much oil it takes to reach the bottom of the spark plug thread. I do this to make sure both cylinders are the same. Swept vol of cyl + your cc / your cc = comp.
Cheers
 Just saw manosound's. I got 10.5:1 in the cafe, but I'm still a month away from 50. *smile*
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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