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#248632 - 04/16/09 9:19 am A65 camshafts  
Joined: Apr 2009
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Billiam Offline
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Billiam  Offline
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Picton, NSW, Australia
Howdy,
I'm elbows deep rebuilding a 1971 Thunderbolt spending waaaaay too much money, and I just received the new camshaft I ordered. I really should know my stuff by now, but I'm not familiar with the A65 camshafts.
I ordered a spitfire grind cam (part number 68-0473) to replace what I assumed was a stock camshaft. The part I took out has 68-473 stamped on it. Problem is, I can't see or measure any difference in the profiles of the two. The new camshaft has no part number stamped on it.
Anybody out there know whether the spitfire and thunderbolt shared the same cam profile? Either I've ordered a stock camshaft or the bike already had the spitfire profile cam in it... my mistake or the bike shops??
Cheers,
Bill


W.

'71 BSA A65T
'71 Honda 500/4
Various unmentionables
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#248634 - 04/16/09 9:36 am Re: A65 camshafts [Re: Billiam]  
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Ger B Offline
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Ger B  Offline
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NL
FWIW.

In my 1971 part number book the part number of the T-bolt camshaft is 68-0473.
I do not know if the Spitfire has a different number.

2c


Ger B

#248638 - 04/16/09 10:41 am Re: A65 camshafts [Re: Ger B]  
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johnnyrvf Offline
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Dordogne, SW France
According to what I have read the unit twin series only used two camshaft profiles and by the time the OIF's arrived BSA were trying to compete performance wise with the spangly new generation Japanese bikes so any thing to boost performance was utilised, I even read somewhere many moons ago that the last year (72) Lightnings had Spitfire pistons fitted but I can't comment on the accuracy of that statement, as to the cam being a Spitfire profile, that would'nt be at all unusual for the year of your bike. Johnny.


What d'ya mean it won't rev to 10?
1965 BSA A65D Lightning Rocket
1976 K*w*s*ki Z900.
1978 Triumph Bonn3ville (930 T160 Powered T140)
1988 H*nd* RC30
1990 Moto Guzzi California 3
1993 Y*m*h* TDM 850
#248646 - 04/16/09 12:03 pm Re: A65 camshafts [Re: johnnyrvf]  
Joined: Aug 2001
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Rich B Online happy
Rich B  Online Happy



Joined: Aug 2001
Posts: 4,949
Stone Creek OH USA
There were only ever 2 camshafts for A65's. There is no "Spitfire" cam or "Spitfire" pistons.

The 68-0473 cam was introduced around 1964 for the Rocket, Spitfire Hornet, and Lightning Rocket models. Post 65, it was utilized in all of the A65's. I doubt it was for unltimate performance as much as for parts commonality, even though the A50's retained the original cam.

All the late bikes used the same 9-1 compression ratio, even the 68 Spitfire's were fitted with the that piston. BSA seemed to shy away from high compression pistons on the A65's after 67.


Life is too short to drink cheap, bad beer.
#248658 - 04/16/09 1:31 pm Re: A65 camshafts [Re: Rich B]  
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Mr Mike Offline
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Mr Mike  Offline
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Cape Carteret, NC
Rich,
So you are saying a Lightning after 67 was pretty much a Spitfire in disguise with some different carbs. Did I get that right?

Mr Mike

#248673 - 04/16/09 2:26 pm Re: A65 camshafts [Re: Mr Mike]  
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Alex Offline
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Alex  Offline

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Seattle
AFAIK, the term "Spitfire Cam" is only correct when used in connection with the A10 Spitfire Scrambler. The term was used in advertisement for Super Rockets using the -357 cam, now known as the "Spitfire Cam".

As rich sez, on unit twins, the "Full Race" cam, as it was called by BSA in its ads was used first on the '64 lightning rocket and by '66 went into all A65's until the end of production. And yes, A65 Spitfires had the same cams, heads and pistons (Excepting '67) as lightnings. The only significant difference in the engines was carburetion.

Last edited by Alex; 04/16/09 2:27 pm.

A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
#248684 - 04/16/09 3:28 pm Re: A65 camshafts [Re: Alex]  
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Lannis Online content
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Lannis  Online Content

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Central Virginia
Same deal with the Hornet, which evolved into the Firebird in 1968. Only engine difference between the Hornet/Firebird and the Lightning was the jetting in the carbs, which was opened up to account for the more open exhausts on the Hornet/Firebird.

Makes it easy to have a practical road bike no matter what bits you start with.

Lannis


OK, I admit it, I'm addicted to brake fluid.

But I can stop any time I want.
#248832 - 04/17/09 12:30 pm Re: A65 camshafts [Re: Mr Mike]  
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Rich B Online happy
Rich B  Online Happy



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Posts: 4,949
Stone Creek OH USA
More like a 68 Spitfire MK IV was a tarted up Lightning. Tank, rims, decals & 32 mm concentrics were about the only major changes from a Lightning to Spitfire.

Reality is, after the closed loop frame bikes ended in 65, the A65's were all based on pretty much a Lightning spec bike that had some cosmetic or carb changes. The bikes that were most different from that common spec were the 66 & 67 Spitfires & Hornets.


Life is too short to drink cheap, bad beer.
#248853 - 04/17/09 2:11 pm Re: A65 camshafts [Re: Billiam]  
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Billiam Offline
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Billiam  Offline
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Picton, NSW, Australia
Good on ya guys, hard to find a straight answer from a bike shop or research alone.. suspected a commonality, but had my doubts with the notorious stubbornness underlying so many aspects of brit bikes.
B.


W.

'71 BSA A65T
'71 Honda 500/4
Various unmentionables
#248936 - 04/18/09 2:51 am Re: A65 camshafts [Re: Billiam]  
Joined: Jan 2006
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Gary E Offline
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Gary E  Offline
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Medford, Oregon
...All the late bikes used the same 9-1 compression ratio, even the 68 Spitfire's were fitted with the that piston. BSA seemed to shy away from high compression pistons on the A65's after 67...

...And yes, A65 Spitfires had the same cams, heads and pistons (Excepting '67) as lightnings. The only significant difference in the engines was carburetion...

...Same deal with the Hornet, which evolved into the Firebird in 1968. Only engine difference between the Hornet/Firebird and the Lightning was the jetting in the carbs,...

...The bikes that were most different from that common spec were the 66 & 67 Spitfires & Hornets...


Aw, but there are differences. There were two different frames in '66 and '67. In '68 the frame was changed. And, since you all are mostly talking about performance, the '68 Firebird Scrambler has the Hornet/'66,'67 Spitfire high compression pistons. Other differences were front brakes and rim, front fender, as well as mufflers and others.

Since I'm a lover of Spitfires I certainly wouldn't say "...More like a 68 Spitfire MK IV was a tarted up Lightning...


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
#248950 - 04/18/09 6:47 am Re: A65 camshafts [Re: Gary E]  
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Redman Offline
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San Francisco
Pistons...brakes...fender, mufflers......like he said..tarted up


Life is short but very wide.
#248951 - 04/18/09 6:50 am Re: A65 camshafts [Re: Redman]  
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Redman Offline
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Redman  Offline
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San Francisco
Sorry...just couldn't resist Gary. All due respect to ya.


Life is short but very wide.
#248965 - 04/18/09 9:53 am Re: A65 camshafts [Re: Gary E]  
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Rich B Online happy
Rich B  Online Happy



Joined: Aug 2001
Posts: 4,949
Stone Creek OH USA
Gary,

I know there are a lot of details bits that are different, especially in 66 & 67, but I was trying to make the point that BSA was working at reducing the parts count. And refuting the internet myth that the Spitfire's had lots of special engine bits, which they didn't, particularl;y cams. That story keeps coming back like a bad penny.

Besides, if you want to really go nuts figuring out BSA parts, get serious about the 62 - 65 unit twins. They can make you crazy with all the differences and detail changes seemingly from month to month. But then you know that from practical experience grin


Life is too short to drink cheap, bad beer.
#248977 - 04/18/09 12:33 pm Re: A65 camshafts [Re: Rich B]  
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Mark Parker Offline
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Mark Parker  Offline
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Bega NSW Australia
I must say for a long time owning a Tunderbolt, or at least the motor in a plunger A10, then a lightning, I always wished I could get the hot Spitfire cam to put in, but as Rich points out they already had it, I think magazine articles might have been responsible for making it seem like the Spitfire had a bigger cam than everything else, (magazines seemed always facinated by cams, if something picked up 2HP from a cam and 10hp from pipes, they'd rave about the cam?)
It is a very good cam, so good, boyers used it in their Triumph twin race bikes, rather than anything else. We use that profile in a modified 750 A65 and it pulls hard to at least 9,000RPM. So if you want to make one faster changing the cam isn't the place to start.


mark
#249081 - 04/19/09 3:02 am Re: A65 camshafts [Re: Mark Parker]  
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Gary E Offline
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Gary E  Offline
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Medford, Oregon
Redman,
I'd say the Lightning is a splashed Spitfire with a fat tank and extra chrome.

Rich, I understand the intent of the information, but I wanted to clear up some of the incorrect portions. After all, misinformation is what keeps the cam rumors going for years. Accuracy here is what keeps this forum credible.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
#249092 - 04/19/09 5:34 am Re: A65 camshafts [Re: Billiam]  
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Billiam Offline
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Billiam  Offline
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Posts: 12
Picton, NSW, Australia
I think the lifespan of the cam myth is due more to the resurfacing of Triumph and Norton cams for various purposes, not least of all racing. Usually termed 'spitfire grind' it comes as no surprise the assumption that L and T BSA twins didn't share it


W.

'71 BSA A65T
'71 Honda 500/4
Various unmentionables
#249095 - 04/19/09 6:59 am Re: A65 camshafts [Re: Billiam]  
Joined: Apr 2005
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Mark Parker Offline
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Mark Parker  Offline
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Bega NSW Australia
Billiam, I get your point, no one is going to say they are useing the std BSA Tunderbolt profile in their super hot Triumph racer are they.


mark
#249103 - 04/19/09 8:43 am Re: A65 camshafts [Re: Mark Parker]  
Joined: Apr 2009
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Billiam Offline
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Billiam  Offline
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Posts: 12
Picton, NSW, Australia
Indeed, I've been thrown off by deceptive marketing once again! I reckon a 390 profile would do more harm than good. Don't suppose anyone is using those specs on road?

Just as an aside, are these forums UK or US based? In Aus myself

Last edited by Billiam; 04/19/09 8:44 am.

W.

'71 BSA A65T
'71 Honda 500/4
Various unmentionables
#249115 - 04/19/09 11:14 am Re: A65 camshafts [Re: Billiam]  
Joined: Apr 2005
Posts: 2,332
Mark Parker Offline
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Mark Parker  Offline
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Joined: Apr 2005
Posts: 2,332
Bega NSW Australia
Billiam, just read your first post! Replacing a spitfire cam with a spitfire cam! Oh well you have a spare I guess, better than just one good cam and one mild one,,,sort of.
This is a world wide forum, started by Morgan in Sweden, I'm also in NSW. Some info:

BritBike.com was established in 1996. BritBike.com is created by British Motorcycle enthusiasts for British Motorcycle enthusiasts. You the visitor and member are most important and your knowledge is highly appreciated by other visitors aspecially on our popular BritBike Forum.
email: morgan@britbike.com
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mark
#249119 - 04/19/09 12:35 pm Re: A65 camshafts [Re: Mark Parker]  
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Billiam Offline
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Billiam  Offline
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Picton, NSW, Australia
Cheers Mark, and not too far away I see.

Seems I do have a spare, at least another excuse to buy another bike to rebuild..

From what I gather the dwell on the later cams is around 281/277 in & out, big change from the pre '65 twins?


W.

'71 BSA A65T
'71 Honda 500/4
Various unmentionables

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