Author Topic: Pistons A10  (Read 1174 times)

Offline pete3000

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Pistons A10
« on: 19.04. 2012 10:53 »
Hello everyone,

I'm new on the forum.
I'm a classic british bike enthousiast since a long time and always wanted to have a BSA A10 as I find this bike lovely !
Well, my dream came true and just bought one that I want to put in RGS configuration. I have find this very nice forum with lots of good infos !
Here is the story.
I have take off the engine, and rebuilt the bottom, and cylinder head. Looking actually for a good gearbox,  but in standard configuration as the RRT2 is hard
to have and difficult to ride the bike everyday with that type of gearbox. 

When I take off the engine, the pistons and barrels were in +.080 but in very good condition, so I decided just to change the rings that I found quite easely.
 GPM pistons in 72 mm were fitted, nice pistons. But when I decided to refit the pistons, a piston felt off my hands and went on the floor, my mistake !
The piston is damage and no more good, (small crack) so I 'm good to find one or buy a pair.

I have made lots of research on the web, but it is impossible to have a GPM in 72 mm.
I have called Cake street classics, but no one answer, probably out,  I will try this afternoon. I have notice that he sells wiseco pistons in 72mm but maybe he doesn't have anymore..., I hope he has some.
I have also find that JP's sells some in 72 mm , but in 7:25.1 ratio, a bit low, I would prefer a higher ratio, like 8:5.1

Any suggestions, advices ?
Thanks a lot for your answer.


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Re: Pistons A10
« Reply #1 on: 19.04. 2012 11:05 »
I built an engine for a mate a couple of years ago and SRM supplied me with +80 pistons. I don't know what make they were. They were 7.25:1. The bike has an iron head and 356 cam, but runs really well, very smooth and pulls like a train. With your alloy head you probably want to stay with the 8.25 pistons. Sometimes (but not always) you get problems with pinking because 8.25:1 is getting towards the limit of compression on A10 engines combined with modern fuel. It would be interesting to know what combination of pistons and cam other people are running and whether they have pinking problems which can or cannot be overcome with manual advance and retard.

Offline pete3000

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Re: Pistons A10
« Reply #2 on: 20.04. 2012 10:50 »
Thank you Beezermacc for the reply. Interesting about the pinking problems.
Got Cakeclassics on the phone this morning, has a pair of Wiseco 72mm, very nice person.
I have ordered him the pistons, will received them shortly, and I will be ready to go on my engine.

Offline 0116harley

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Re: Pistons A10
« Reply #3 on: 20.04. 2012 21:41 »
Hi all
when i rebuilt the motor on my A10 iron head i was looking at putting 7.25:1 pistons in. But for some reason was having trouble getting hold of these pistons at the time, so was adviced to use 8.25:1 pistons. On the first test run the motor did start pinking . After retarding the timing slightly and running the bike a little richer problem is now solved. the motor pulls great no pinking.
cheers Neil