Author Topic: CAM / Piston selection  (Read 1273 times)

Offline Josh Cox

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CAM / Piston selection
« on: 05.06. 2009 13:16 »
Have done a search here, did not find answers.

Am having a rebuild done on an A10, Capt Orabanda ESQ has suggested 7.25 hepolites with the 356 CAM, sounds fantastic to me, and having heard his machines on youtube, am very exited about what my bike may sound like.

But,,,,,,, I want to know more, how does one correlate with any certainty without the sagely advice,, just curious ?.

Have had a flick through Roy Bacons twin book, this left me with even more questions, for example, there are 14:1 pistons listed, which CAM ?.

Cheers.
Black 1953 Golden Flash Plunger

Online A10Boy

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Re: CAM / Piston selection
« Reply #1 on: 05.06. 2009 14:54 »
I've seen those 14:1 pistons listed on ebay - I had to laugh, could you imagine??

In my own humble opinion, choosing pistons and cams for our BSAs for ROAD use is a matter of looking at what different models had fitted from the factory, and deciding which character you want to have and copy that specification. In other words, if you want a smooth and steady tourer use the later Flash set up [7.25:1 pistons and 356 cam] and if you want a faster more lively engine, but one which is less drivable, then go for the "Spitfire" 357 Cam and higher compression piston set up.

It all depends what you want from the bike, a "Touring" set up is much less stressful on the engine and it will last much longer. Also, sporty engines really do need the Alloy head to assist with cooling otherwise they pre-ignite badly.

Again, just my opinion, but 14:1 pistons have no place in any BSA engine,- apart from one which is built specifically for and dedicated to the drag strip - you would probably need to have a cam made to suit 14:1 pistons.

Unless you know differently -----
Regards

Andy

1958 Super Rocket
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline Josh Cox

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Re: CAM / Piston selection
« Reply #2 on: 05.06. 2009 15:02 »
Certainly do not know differently. *smile*

Maximum noise and bling value.

I get my speed thrills at work.

Black 1953 Golden Flash Plunger

Offline rocket man

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Re: CAM / Piston selection
« Reply #3 on: 06.06. 2009 11:24 »
can you emagine kicking up a bsa with 14:1 pistons in it youd need an elephant to kick it up  *smile*

Offline LJ.

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Re: CAM / Piston selection
« Reply #4 on: 06.06. 2009 11:30 »
can you emagine kicking up a bsa with 14:1 pistons in it youd need an elephant to kick it up  *smile*

... and kicking back at you as well. Ooer!  *help*
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline rocket man

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Re: CAM / Piston selection
« Reply #5 on: 06.06. 2009 16:23 »
youd need a space helmet if it kicked back *smile*