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A65 cam in an A50 #3135
06/23/05 12:11 pm
06/23/05 12:11 pm
Joined: Jun 2005
Posts: 97
montreal
J
johnnie690 Offline OP
BritBike Forum member
johnnie690  Offline OP
BritBike Forum member
J
Joined: Jun 2005
Posts: 97
montreal
I"m just about to fit an A65 cam in an A50(1969)motor,Ive been told there is no problem.I see that the overall lift is about .040 more on the A65 and the deration of course is different,anything else to worry about.

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Re: A65 cam in an A50 #3136
06/23/05 2:07 pm
06/23/05 2:07 pm
Joined: Aug 2001
Posts: 5,099
Stone Creek OH USA
R
Rich B Offline

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Rich B  Offline

BritBike Forum member
R
Joined: Aug 2001
Posts: 5,099
Stone Creek OH USA
No.


Life is too short to drink cheap, bad beer.
Re: A65 cam in an A50 #3137
06/23/05 2:19 pm
06/23/05 2:19 pm
Joined: Jun 2005
Posts: 97
montreal
J
johnnie690 Offline OP
BritBike Forum member
johnnie690  Offline OP
BritBike Forum member
J
Joined: Jun 2005
Posts: 97
montreal
Thanks Rich B,I'll now carry on with the build up.I just wanted to make sure as I don't want to do this job over again ,I have 2 ,A65 cams and no good A50 cams.Thanks

Re: A65 cam in an A50 #3138
06/24/05 10:59 am
06/24/05 10:59 am
Joined: Aug 2001
Posts: 319
Hesperia, CA
L
LDBennett Offline
BritBike Forum member
LDBennett  Offline
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L
Joined: Aug 2001
Posts: 319
Hesperia, CA
johnie690:

While you may not care, the Lightning cam from most 650 twin carb bikes is a bit cammy. The motor will jump on the cam at about 3000 to 4000 RPM. The mild nature of the A50 will probably be lost with the cam transplant.

The Lightning/Spitfire/Hornet cam is hotter than the Triumph Bonneville cam, for instance, and the cammyness is readily apparent even on my low compression A65.

This is not a negative for the transplant, but only a heads up.

LDBennett

Re: A65 cam in an A50 #3139
06/25/05 4:23 am
06/25/05 4:23 am
Joined: Aug 2001
Posts: 3,348
Michigan, USA
BONZO R.I.P. Offline
In Remembrance
BONZO R.I.P.  Offline
In Remembrance
Joined: Aug 2001
Posts: 3,348
Michigan, USA
I dont think you will end up with any cam issues , as LD says , it will have a different personality , but you noted that with lift and duration . The only thing I would add is to replace valve springs , I dont know for sure if A-50 are a different spec , but I do know thta if they havent been changed recently , they are probably 30+ years old and tired of being kept under tension .i'm sure it is second nature to most , but changing out valve springs is cheap insurance , as long as you buy quality replacements(BTW , Hotrod springs arent necessarily a good thing in a street engine, factory spec replacements should be sufficient, the cam dictates the springs ) .

FWIW-BONZO

Re: A65 cam in an A50 #3140
06/25/05 11:48 am
06/25/05 11:48 am
Joined: Aug 2001
Posts: 319
Hesperia, CA
L
LDBennett Offline
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LDBennett  Offline
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L
Joined: Aug 2001
Posts: 319
Hesperia, CA
Bonzo:

My 1966 Parts Book says they are the same parts (valve springs). I don't know about later motors.

I would add that it is a good idea to have the entire valve train serviced (guides, valves, valve grind, and springs) as necessary.

LDBennett

Re: A65 cam in an A50 #3141
06/26/05 12:06 am
06/26/05 12:06 am
Joined: Aug 2001
Posts: 5,099
Stone Creek OH USA
R
Rich B Offline

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Rich B  Offline

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R
Joined: Aug 2001
Posts: 5,099
Stone Creek OH USA
Unit twins (A65) had 2 sets of valves. 62 - 65, 66 - 72. Never paid much attentionto the A50, but know they had at least one change.


Life is too short to drink cheap, bad beer.
Re: A65 cam in an A50 #3142
06/26/05 12:18 am
06/26/05 12:18 am
Joined: Aug 2001
Posts: 3,348
Michigan, USA
BONZO R.I.P. Offline
In Remembrance
BONZO R.I.P.  Offline
In Remembrance
Joined: Aug 2001
Posts: 3,348
Michigan, USA
My thinking with the previous post was two things , first , I have seen people replace valves and guides and reuse the original springs because they arent broken and are still in spec? if they bothered to check spec.It maybe a non issue , I have never seen a broken or collapsed spring cause a catastrophic filure in a Britbike , but it never made sense to me . second ,I have probably seen more than my share of boy racers who install highperformance valve springs , thinking they are just plain better than original replacement even without a hot cam , and end up wasting their cam , and probably losing performance in the deal before the cam goes south .

As Rich says , there were some differences in valves , springs , collars and retainers in various years , I dont know if the A-50 and A-65 kept pace with these changes . It seems info is sketchy on the A-50 compared with the A-65.

-BONZO

Re: A65 cam in an A50 #3143
06/28/05 12:49 pm
06/28/05 12:49 pm
Joined: Jun 2005
Posts: 97
montreal
J
johnnie690 Offline OP
BritBike Forum member
johnnie690  Offline OP
BritBike Forum member
J
Joined: Jun 2005
Posts: 97
montreal
Points well taken concerning valve springs etc,bottom end is together and I'll make another posting about how it runs sometime next week.Thanks for all for your opinions and info .J

Re: A65 cam in an A50 #3144
06/28/05 5:14 pm
06/28/05 5:14 pm
Joined: Jun 2004
Posts: 154
Indianapolis, IN
S
Sonic Twin Offline
BritBike Forum
Sonic Twin  Offline
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S
Joined: Jun 2004
Posts: 154
Indianapolis, IN
I believe I was once told that BSA only made two different cam grinds for the unit twins. These break down roughly into the single carb and twin carb models. The hotter cam, which came in the Lightning and Spitfire as well as the Cyclone and Wasp, was 68-473. This cam works equally well in either 500 or 650 application. When you put the top end together on the 500, check very carefully for coil binding and for the valve collar/keeper hitting the top of the guides. The valve stems on the 500 are longer because the chamber is smaller so some parts are different while others are the same, between 500 and 650. I believe rocker arms and pushrods are the same, but not sure. Just make sure the parts don't run into each other. Many of the Daytona 500's failed back in 66-69 era due to swallowing valves. SRM once told me that the factory race engines actually ran the 68-473 cam, that they could never improve on that. Though I do have a couple of Sifton grinds that are pretty scary.

Re: A65 cam in an A50 #3145
06/28/05 6:51 pm
06/28/05 6:51 pm
Joined: Sep 2002
Posts: 7,813
Seattle
Alex Offline

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Alex  Offline

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Joined: Sep 2002
Posts: 7,813
Seattle
Only the 500 road versions and early 650's used the 69-103 cam according to the parts manuals. By '64, all 650's used the -473 cam.


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
Re: A65 cam in an A50 #3146
06/29/05 11:27 am
06/29/05 11:27 am
Joined: Aug 2001
Posts: 319
Hesperia, CA
L
LDBennett Offline
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LDBennett  Offline
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L
Joined: Aug 2001
Posts: 319
Hesperia, CA
alex:

According to the 1966 parts book the A50 Royal Star used the 68-0103 while the all A65's and a A50 Wasp used the Lightning cam 68-0473. I know, parts books can be wrong but that ceratinly makes the most sense to do it that way for a grocery getter, commuter bike like the heavy for a 500 A50. Oh, I forgot, we're talking about a Brit bike where logic does not always prevail. In practice they may indeed have all come with the same cam (????).

Sonic twin:

Look at the specs on the Lighning cam. It is a step above any stock Triumph cam, which was the race bike of the 1960's. It would not surprise me that nothing else worked better all around.

LDBennett

Re: A65 cam in an A50 #3147
06/29/05 12:50 pm
06/29/05 12:50 pm
Joined: Sep 2002
Posts: 7,813
Seattle
Alex Offline

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Alex  Offline

BritBike Forum member
Joined: Sep 2002
Posts: 7,813
Seattle
Oops, I meant 68-103. Typo.

I think we're seeing the same things, otherwise, LD. Wasp and Cyclone Competition had the -473, while Cyclone road had the -103 cam.

Cheers. pint


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.

Moderated by  Allan Gill, Jon W. Whitley 


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