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A65 '64 or '66? Decisions, decisions... #769264
03/26/19 4:06 am
03/26/19 4:06 am
Joined: Sep 2014
Posts: 61
portland or
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drunkenmonkz Offline OP
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Joined: Sep 2014
Posts: 61
portland or
So ive been posting lately with questions regarding my 64 a65 lightning motor rebuild. People have been really helpful so far! It started with a pretty good condition core motor. i had originally planned on freshening up and running as a thunderbolt head back up motor for when i pull my 68 lightning runner to rebuild. Well, ive pretty much deviated from the freshen up thing with an srm oil pump, map connecting rods, ARD cdi/mag, the later cam and an alloy primary belt drive setup. So... i have a good set of 66 cases that ive been hanging on to and am considering using them instead.
Is there any benefit to running the 66 cases instead of the 64? Will the crank from the 64 fit in the 66? What would i need to do to run the 64 internals in the 66?
Ive been planning on running a thunderbolt head to simplify things, what options are there for getting some more get up and go with the t-bolt head? Carburation/Porting options? I have a couple lightning heads i could pick from to use but everything ive read tells me the nominal benefit of the duel carbs isnt really worth it. While my lightning is solid and runs well i am familiar with the downfalls of the twin carb setup.
Thanks for your input guys!

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Re: A65 '64 or '66? Decisions, decisions... [Re: NickL] #769288
03/26/19 1:17 pm
03/26/19 1:17 pm
Joined: Sep 2014
Posts: 61
portland or
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drunkenmonkz Offline OP
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portland or
Originally Posted by NickL
66 + uses a roller ds main, 64 = ball race. Any year crank will fit any year motor with fiddling.
The single carb head can be flowed easily to get more urge and bigger i/l valves fitted.
You don't have to do much to improve things quite a lot. Going mad will spoil the t'bolt characteristics.
I used a dcoe 40 weber on a modified t'bolt head very successfully when racing.



NickL, so same comfiguration setup as my 68 then. I dont have to use/make any special adapters or spacers...?
How does one source bigger inlet valves? And i dont think theres anyone in my area that is familiar with these old bsa's enough to know how to flow a head, is that someone could do themselves? Ive got machining and fabrication tools so... It seems like twin 930 carbs was excessive for the lightning but a single is fine for the t-bolt stock setup. Would i have to swap to a bigger carb or is there something more "mild" i can do to it and keep the 930 carb? Contrary to how much im spending on this motor, im not planning on racing it. Doing these upgrades is to get the most reliable a65 i can. i figured since im noodling about with it might as well see if theres anything to be able to get a few more mph out of her every now and them without going "full race"

Re: A65 '64 or '66? Decisions, decisions... [Re: drunkenmonkz] #769312
03/26/19 6:21 pm
03/26/19 6:21 pm
Joined: Sep 2004
Posts: 1,040
Farnham, Surrey, UK
gunner Online content
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gunner  Online Content
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Farnham, Surrey, UK
I think what your asking for is kind of contradictory, if you want reliability then stick with the standard single carb and valve sizes, if you want a few more mph then be prepared to spend hours and hours messing around with bigger carbs, valves, gas flowing etc.

Personally I would stick with the standard Thunderbolt setup but I you wanted more power I would ask Ed at E&V Engineering for advice, see https://www.shopevengineering.com/


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: A65 '64 or '66? Decisions, decisions... [Re: drunkenmonkz] #769382
03/27/19 1:21 pm
03/27/19 1:21 pm
Joined: Dec 2002
Posts: 462
Chelmsford MA
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MarcB Online content
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Chelmsford MA
The 66+ drive-side case (left side) is machined for a wider crank. Your early crank will fit but BSA widened the left-side counterweight on 66+ cranks to re-center the rods. You would have to do a lot of shimming to make up the difference and I don't know what that would do for your alternator alignment. Later cranks in good conditions are readily available, though, so it could just be a matter of "try it and see".

The gains from using the 66 cases are minimal. Timing plug on the front, alternator bracket, lose the speedo... I can't think of anything else. More headaches, maybe?

Re: A65 '64 or '66? Decisions, decisions... [Re: drunkenmonkz] #769384
03/27/19 1:49 pm
03/27/19 1:49 pm
Joined: May 2013
Posts: 5,610
West Yorkshire
Allan Gill Offline

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Allan Gill  Offline

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Joined: May 2013
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West Yorkshire
I fail to see how changing valves and port sizes etc will make anything more or less reliable. If it’s built like someone literally threw it together then even with all the stock bits on will still have potential for blowing up or being in-reliable. If you haven’t done all what you can to make the motor quite strong (properly ground crank without the journal radius machined away, decent rods etc) then any extra performance search will show itself up, although any motor will show this much quicker if you lug it like a hog.

I’ve had a lot of success with the small port head and 928 Concentrics, I also find little improvement in the smaller 38mm valves and the later 40mm (am I right in saying that the last of the Super rockets had 38mm?) if anything I find I loose a little at bottom end and gain right at top end but not enough gain for it to be worth it on the street. Last thing I would also do is make the ports bigger, I’ve spent more time making them smaller. The best upgrade I’ve ever fitted to a motor has been the SRM race cam, their race valve springs and followers ground to 1.125” radius. It pulsing top from 1500 rpm and just keeps revving at the top. I infect changed it for the mega cycle X12 cam (had to one the bushes out as the shafts were over size otherwise the SRM cam would be back in there) but whilst the X12 is an improvement over the stock lightning cam, it’s still not as powerful as the SRM part. (That said the stock lightning cam retarded a few degrees does work quite well and adds more grunt).

I’d stick with your standard thunderbolt head though and see how much better you can get the motor to run with just that.


beerchug
Re: A65 '64 or '66? Decisions, decisions... [Re: drunkenmonkz] #769391
03/27/19 3:40 pm
03/27/19 3:40 pm
Joined: Apr 2005
Posts: 1,758
Mississauga, Ontario.
A
Adam M. Online content
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Adam M.  Online Content
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Posts: 1,758
Mississauga, Ontario.
Allan you downsized your double carb big port, big valve head, Nick L advise was about stock one carb Thunderbolt head.
I'm big fun of stock Thunderbolt head left stock, easy starting, gobs of torque down low in every situation and enough top end for today traffic, but your bike stays together.
After 40 min ride with my friend with speeds around 90 mph on my double carb A65 I spent 2 days wrenching to get it back to the shape i started with:).

Re: A65 '64 or '66? Decisions, decisions... [Re: Adam M.] #769394
03/27/19 4:06 pm
03/27/19 4:06 pm
Joined: May 2013
Posts: 5,610
West Yorkshire
Allan Gill Offline

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Allan Gill  Offline

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Joined: May 2013
Posts: 5,610
West Yorkshire
Originally Posted by Adam M.
Allan you downsized your double carb big port, big valve head, Nick L advise was about stock one carb Thunderbolt head.
I'm big fun of stock Thunderbolt head left stock, easy starting, gobs of torque down low in every situation and enough top end for today traffic, but your bike stays together.
After 40 min ride with my friend with speeds around 90 mph on my double carb A65 I spent 2 days wrenching to get it back to the shape i started with:).


That’s unfortunate, I usually have to top the oil up.

I’ve reworked several heads, some started as small ports and some 30mm, some have gone larger still and had the floor filled (more like Mark Parker’s) and some had nothing done but the floor raised. The best one was small port and reduced the port height further to 19mm. I’ve also ridden various different A65T’s with standard head.... thing is the Thunderbolt head is much the same as the small port twin carb head, there are some differences where the port turns to the valve, but apart from top speed they are very similar.

The head on mine at the moment is a small port one with 40mm valves fitted. PES did a multi angle job of the seats (so much you can barely tell there is any angle there, I can’t feel an edge between the cuts).

Last edited by Allan Gill; 03/27/19 4:07 pm.

beerchug
Re: A65 '64 or '66? Decisions, decisions... [Re: NickL] #769588
03/29/19 10:49 pm
03/29/19 10:49 pm
Joined: Aug 2001
Posts: 730
San Luis Obispo, CA
Richard Phillips Offline
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Joined: Aug 2001
Posts: 730
San Luis Obispo, CA
I have found some of the early LR A65 crankshafts.090 shorter or less wide then later crankshafts.
The cases were also cast to suit and can be identified as not having a time plug boss/hole and a very low searial number.
Pretty sure I’m correct however always good to check what you got.
I’m not convinced there is a difference using a ball bearing vrs roller bearing on any of the crankshafts.
I prefer the roller bearing and a solid timing side bushing lined bored and honed.
One other difference in the earlier cranks is the sludge trap has access on both sides.
Good luck and remember “To Measure Is To Know.”



Re: A65 '64 or '66? Decisions, decisions... [Re: Allan Gill] #769747
03/31/19 8:28 pm
03/31/19 8:28 pm
Joined: Sep 2014
Posts: 61
portland or
D
drunkenmonkz Offline OP
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drunkenmonkz  Offline OP
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Joined: Sep 2014
Posts: 61
portland or
Originally Posted by Allan Gill
I fail to see how changing valves and port sizes etc will make anything more or less reliable. If it’s built like someone literally threw it together then even with all the stock bits on will still have potential for blowing up or being in-reliable. If you haven’t done all what you can to make the motor quite strong (properly ground crank without the journal radius machined away, decent rods etc) then any extra performance search will show itself up, although any motor will show this much quicker if you lug it like a hog.

I’ve had a lot of success with the small port head and 928 Concentrics, I also find little improvement in the smaller 38mm valves and the later 40mm (am I right in saying that the last of the Super rockets had 38mm?) if anything I find I loose a little at bottom end and gain right at top end but not enough gain for it to be worth it on the street. Last thing I would also do is make the ports bigger, I’ve spent more time making them smaller. The best upgrade I’ve ever fitted to a motor has been the SRM race cam, their race valve springs and followers ground to 1.125” radius. It pulsing top from 1500 rpm and just keeps revving at the top. I infect changed it for the mega cycle X12 cam (had to one the bushes out as the shafts were over size otherwise the SRM cam would be back in there) but whilst the X12 is an improvement over the stock lightning cam, it’s still not as powerful as the SRM part. (That said the stock lightning cam retarded a few degrees does work quite well and adds more grunt).

I’d stick with your standard thunderbolt head though and see how much better you can get the motor to run with just that.



So sounds like the 64 cases are the route im going to go as the internals are out of it and there seems to be no advantage to going with the 66. Taking your advise and just going with the stock setup on the t-bolt head. I read on srm's website that they recommend the race cam be used for the big bore setup. I had kind of ruled it out because of that but it sounds like you really liked how it performed with the motor stock(ish)? Where did you have the cam followers ground to the 1.125" and, i guess, why?


Moderated by  Allan Gill, Jon W. Whitley 

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