Author Topic: Strange A10 Crankshaft  (Read 1117 times)

Offline Swarfcut

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Re: Strange A10 Crankshaft
« Reply #15 on: 06.02. 2019 12:02 »
 Now you know what a small journal crank looks like inside.  As GB says, get that other plug out, the cavity behind it will also be well clogged up.
   The plugs were never (or rarely) removed for the oilway to be cleaned out, back in the day. The crank grinder took your money, and in a matter of a few short weeks there was a good chance you would be back again for another grind. In the Service Sheet, 206, Engine Dismantling, it gets just two short sentences, a matter of four lines of print.  Most owners, including me, looked at the plugs, reckoned they were in there for life, and just flushed it through with paraffin, little realising what was inside.

  As it is a rare crank I would only have it ground if the journals are worn or scored. If still within size and not worn oval (there is a suggested 2 Thou ovality limit) you may get away with just a  journal polish, which is the final stage in grinding a crank. Essential to ensure no sharp edge to the journal oil supply holes, a sharp edge will gouge a groove your new shells. Lots of information on the Glyco Bearings Website.

 Same with the timing side journal.  Only grind off the minimum to clean it up and go for a one piece custom bush, line bored to fit the crank.

 Swarfy.

Offline cyclobutch

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Re: Strange A10 Crankshaft
« Reply #16 on: 06.02. 2019 12:38 »
I don't think you can get extra torque output from a crank whether it's heavy or light, as in measured continuos torque output on a dyno.
The heavy flywheel does give extra momentum, which makes starting off without stalling easier. The downside is they are a little slower to rev up.
I once had an Ossa race bike that came with three external flywheels, two aluminium in different weights and a heavy bronze.
It had the bronze flywheel fitted, so I switched for the lighter al. job. It revved noticeably quicker, which was fun for awhile, but I soon tired of kickstarting it after multiple stallouts when used in stop start off roading. The bronze wheel went back on.

Glen

I also enjoy the extra engine braking of a lighter flywheel. Toying with having the flywheel lightened on my T3 when I pull it out in a couple of weeks time - and that's to speed up the gear change a little.
Various, including ...
'58 Iron Head Flash Bitza


Online berger

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Re: Strange A10 Crankshaft
« Reply #17 on: 06.02. 2019 16:16 »
well for anyone interested an A7 crank -10 thou weighs 14lbs and its flywheel without the 6 nuts and bolts is 8lbs- just thought I would mention it because no pub until friday *beer* A10 cranks are bigger too *smile*

Offline muskrat

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Re: Strange A10 Crankshaft
« Reply #18 on: 06.02. 2019 18:50 »
I lightened my A7SS racer crank by about 3 Lb. The flywheel looked like Swiss cheese. Revved out to 7500rpm very quickly. Needed a fist full to get off the line.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline Servodyne

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Re: Strange A10 Crankshaft
« Reply #19 on: 06.02. 2019 19:34 »
As GB says, get that other plug out, the cavity behind it will also be well clogged up.

Ok, You and GB are obviously correct, it's not worth the risk in trying to save any effort in removing the drive side plug. It's just that the timing side was such a pig to get out, hopefully the drive side won't be any more difficult.
The crank will need a regrind unfortunately, as it's around a thou under bottom tolerance on all journals. I'm just amazed that sufficient oil was able to get through at all and that the journals are as good as they are.
My plan for the crank was to replace the later one that's fitted to my 57 Spitfire even though it's post engine no CA10 SR.231 and has the correct crank fitted. I was going to upgrade it with billet conrods and raise the compression ratio from 8.25:1 to 9:1 with some new pistons that I've recently acquired, but after reading some of the comments re the heavy crank I might have a rethink.
Thanks for all the replies.
Jim
1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando

Offline Swarfcut

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Re: Strange A10 Crankshaft
« Reply #20 on: 06.02. 2019 20:28 »
The remaining plug knows what's coming.....you will have no problem. If you sacrifice it, replacements are readily available.

 Swarfy.

Online Greybeard

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Re: Strange A10 Crankshaft
« Reply #21 on: 06.02. 2019 21:47 »
... replacements are readily available.
With hex sockets

Offline Servodyne

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Re: Strange A10 Crankshaft
« Reply #22 on: 07.02. 2019 12:57 »
As GB says, get that other plug out, the cavity behind it will also be well clogged up.
  Swarfy.
I'm really glad I listened to you two. I had to get a bit medieval with the drive side plug but it was well worth the effort. I had thought that if it was 1/4" all the way through, I should be able to clean it out good with a long 1/4" drill and hole brush. I didn't expect it to be 9/16 in diameter all the way to the flywheel from the drive side, so I would never have been able to clean it out properly. 
Good advice
Cheers Jim

1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando

Online Greybeard

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Re: Strange A10 Crankshaft
« Reply #23 on: 07.02. 2019 17:22 »
 *smile*