G12 vs BSA Road Rocket A10

[TrevorCSR]

The BSA twins and AMC twins are basically equal. As most British bikes of that period were. Both have their good and bad points. What really matters is the condition of the bike you are buying. If you know of a GOOD G12 for sale, then buy it.

[Matchymarty]

A road test by MOTO REVUE in 1961 for the G12CSR = 180 KPH - It was the fastest bike ever tested by them (including BSA, TRIUMPH, NORTON, R.E....).
You can see this road test, translated in English, in Jampot number 588 - July 2001.
Just a question : what is the distance from your home to your office ?
In 1965 I had a 1957 600 AJS 30 wich runned easily on rather long distances between 110 et 140 Kph,(no speed limits in France at this time !) and was very confortable, with a nice handling. The top speed was 156 Kph, exactly as a 99.
1958 G11/30 have alloy primary chaincase.
But obviouly the G12/31 have more torque.

I'll look up the Jampot Thanks for the reference. Love reading old reviews etc. Great stuff.
Distance from home to work is 73km (45 miles) up the motorway or if I take the 'Matchy way', its precisely 112km or 70 miles. The long way I take on the old bikes is a 2 hour trip - which equates to 4 hours travelling in the day, where as my normal run on my 2012 Bonneville up the motorway is 55-60 mins.

Spoke to a friend in my Matchy club the other day and he was saying 650's had a habbit of breaking crankshafts? Any comment on that?

Good to know the 600's are also happy at 100-110kph. This is the sort of bike i'm looking for.

[clive]

Rob H,
I think that you may be referring to Vic Willoughby's 102.9 miles in an hour in 1958 on a G11CSR. It is referenced in this site http://www.jampot.com/article_print.asp?id=20
John

Just what I was thinking John, good to meet today sorry I forgot the garage keys or you would have seen my 58 G11CS

[Rob Harknett]

Also, referring to Matchless taking first 6 places at Thruxton 500 mile race. I seem to recall something about Matchless G50 taking 6 out of 10 places somewhere, some time. ????? Maybe it was that which all got mixed up in a conversation years ago.

[TrevorCSR]

Interesting point that, crankshafts breaking. I think it's a lot of media hype and hearsay. I don't know anyone that has broken a crankshaft. Seems like the media, like nowadays, picked up on a ‘few' 650s that HAD broken crankshafts, and it was no doubt proliferated by the other marques.
Of course, that adds to the scarcity and value of second hand cranks. I had three generator (dynamo) cranks that I held on to for (30 plus) years. Doubtless many others have done the same. And I'm sure that AMC did not produce the sheer volume of bikes the other major manufacturers did. I don't remember there being that many AMCs around in the 60s and 70s
I was offered and bought a 1959/60 G12 Matchless in the early 70s. That would NOT have had a “spheroidal nodular graphite” crankshaft. I thrashed that, as you do when you are in your early 20s. Sold it on to a mate and he could not break it either, and he was well known for trashing engines.
I've seen evidence of major engine damage on AMC twins, i.e. damage where a conrod has opened a breather hole in the crankcases, BUT I've seen that on BSAs and Triumphs as well. A con rod usually breaks through lack of lubricant to the big end bearing.
Buy yourself a good AMC twin and enjoy it.

[Duncan]

Hi Trevor, I can strike up two 650 cranks in the last ten years (+25,000 miles) , so not hype, however I do not see it as a reason not to buy a bike its just luck of the draw, every bike will have its issues, BSA's tends to be a very poor/appalling cable operated rear brake.

[Matchymarty]

A road test by MOTO REVUE in 1961 for the G12CSR = 180 KPH - It was the fastest bike ever tested by them (including BSA, TRIUMPH, NORTON, R.E....).
You can see this road test, translated in English, in Jampot number 588 - July 2001.
.........
Spoke to a friend in my Matchy club the other day and he was saying 650's had a habbit of breaking crankshafts? Any comment on that?

Good to know the 600's are also happy at 100-110kph. This is the sort of bike i'm looking for.

I Tried looking at the archives and Back Issues on Jampot.com, but they don't have issues back to 2001. Bummer. If anyone knows how I can read the issue noted above, much appreciated!

Also, the gent I was talking to recently has had Matchy twins all his life and has also broken 2 cranks. He believes its due to the funny oiling setup to the bottom end and worn pumps.

[TrevorCSR]

I'm interested to know the circumstances of your crankshaft breakages. Were the motors running fine? Timing spot on? Carburation? Oil supply? Did a conrod let go first? Engine speed? Under load?
As for poor REAR brakes, how about an abysmal CABLE operated 7” diameter by 7/8” wide shoe FRONT brake?
Moderators: WHY do we have an American spell chequer???

[TrevorCSR]

"Also, the gent I was talking to recently has had Matchy twins all his life and has also broken 2 cranks. He believes its due to the funny oiling setup to the bottom end and worn pumps."

Can you explain 'funny oiling setup to the bottom end'?
Worn pumps would not be able to supply enough oil to the big ends. The bearings will run and the conrods will break.

[Matchymarty]

Trevor,
I'm not 100% across his meaning of the 'funny setup for oiling' and I'm not familiar in detail with the pump etc for the twins, I think he meant that the oil has to be pumped though crank then to bearing internally?
I'll ask him next time I'm talking to him.