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How many A70s did BSA produce? #735522
05/16/18 11:26 am
05/16/18 11:26 am
Joined: Nov 2010
Posts: 2,957
Boston, Massachusetts, USA
kurt fischer Offline OP

#irideslow
kurt fischer  Offline OP

#irideslow
Joined: Nov 2010
Posts: 2,957
Boston, Massachusetts, USA
How many A70s did BSA produce, and when?

Just curious.

Thanks,


Kurt
1968-70-71 Triumph TR6R Bitsa - 1969 Triumph TR6R - 1971 BSA A65L - 1973 Triumph TR5T
2005 Ducati MTS 1000S DS - 2012 Ducati Hyper 796 - 2014 Kawasaki ZX1000
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Re: How many A70s did BSA produce? [Re: kurt fischer] #735526
05/16/18 12:23 pm
05/16/18 12:23 pm
Joined: Dec 2004
Posts: 9,293
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,293
Scotland
For production competition they had to produce minimum of 200 (like the 750 T120RT) so low 200's would be an educated guess, timing would be to meet the racing season.

Re: How many A70s did BSA produce? [Re: kurt fischer] #735530
05/16/18 1:20 pm
05/16/18 1:20 pm
Joined: Aug 2001
Posts: 3,803
argyll. scotland, uk
gavin eisler Offline
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gavin eisler  Offline
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Joined: Aug 2001
Posts: 3,803
argyll. scotland, uk
Burtons have a page and register for A70s, they reckon around 200.
see here
https://burtonbikebits.net/bsaa70/


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: How many A70s did BSA produce? [Re: gavin eisler] #735560
05/16/18 5:50 pm
05/16/18 5:50 pm
Joined: Nov 2010
Posts: 2,957
Boston, Massachusetts, USA
kurt fischer Offline OP

#irideslow
kurt fischer  Offline OP

#irideslow
Joined: Nov 2010
Posts: 2,957
Boston, Massachusetts, USA
Excellent. Thanks to you both.


Kurt
1968-70-71 Triumph TR6R Bitsa - 1969 Triumph TR6R - 1971 BSA A65L - 1973 Triumph TR5T
2005 Ducati MTS 1000S DS - 2012 Ducati Hyper 796 - 2014 Kawasaki ZX1000
Re: How many A70s did BSA produce? [Re: kurt fischer] #735565
05/16/18 7:34 pm
05/16/18 7:34 pm
Joined: May 2018
Posts: 64
Oregon, USA
S
Sluggo650PNW Offline
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Sluggo650PNW  Offline
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S
Joined: May 2018
Posts: 64
Oregon, USA
Need a flywheel for one? I have some old warehouse NOS stock still in the wrapping, Some accounts have way more spares than bikes produced, I dont know for sure but several ex dealers told me that.

Re: How many A70s did BSA produce? [Re: kurt fischer] #735567
05/16/18 7:39 pm
05/16/18 7:39 pm
Joined: Jun 2013
Posts: 92
Texas, USA
R
Ray Elliott Offline
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Ray Elliott  Offline
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R
Joined: Jun 2013
Posts: 92
Texas, USA
I'll take one if you have the crank to put with it!


Ray Elliott
---
A65, A70, A75, T120, T140, T150, T160
Re: How many A70s did BSA produce? [Re: Ray Elliott] #735573
05/16/18 8:38 pm
05/16/18 8:38 pm
Joined: May 2018
Posts: 64
Oregon, USA
S
Sluggo650PNW Offline
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Sluggo650PNW  Offline
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S
Joined: May 2018
Posts: 64
Oregon, USA
I would be a wealthy man *IF* I had All the A70 bits and could sell as a kit, A65 motors are not hard to find and generally inexpensive. BSA Made a number of flywheels of different weights and slightly different appearance, They ALL Bolt up from what I can tell, And have played around with different weight flywheels on a few builds with interesting results. (Dynamically balanced as well-Key component) I dont have my part number sheet handy with all the numbers associated with these Flywheels (I have a lot of them) but if its something someone is interested in, PM me. The flywheels themselves ARE in the original factory packing. I DO have 2-3 NOS flywheels as well, but undetermined if they are plain jane A65 or something more exotic. Most of my stuff has been in deep storage last 15 years so going thru and sorting parts and bits.

I have some of the late A10 cranks that people tend to get excited about as well, And after assignment to my A10 projects I believe I might have a few extra, and debating about building a hotted up A65 or other monstrosity.

I used to quizz and pick the brains of many of the old racers, Some would tell you some wild stories over beers and a few of them were actually true, But it was common back in the day to
do a "Dis-Information" campaign to throw off your competitors mining for gold, I have some great stories about that as well, But along the way picked up some great tidbits that panned out. Used to be a well known west coast racer and builder who went by "Captain Dirt" and the good captain was a mainstay in the racing community with many makes and brands. Sadly RIP but one day at a AMCA event I got him talking about his BSA race bikes he built. There is a huge amount of variables (Gearing, type of track, and rider) But on the short TT and flat tracks here, He had a combo that worked well. (Sidewinders, Castle Rock, Idaho, and Rainier).

His formula for the 650 (He built some 750s too) was take New late A65 rods, replace the caps with Norton, New Bolts and resize them to optimum spec. He felt that the all alloy rods grew too much under use and loosened up, Some other anecdotes on this elsewhere seem to support that theory, Then find the lightest BSA Flywheel you can (Hence my NOS collection) and then lighten it up to the lightest 650 Triumph weight. Triumph played around with flywheel weights as well, And this is not from my notes but memory so IIRC it was a 66 Triumph that was lightest??? Anyrate, the weight diff is significant. 4 lbs IIRC,, and not easy to shave them down that much,. My balancing guy did the lightening and we got close but not the exact same weight. (A billet crank assy would be the solution, only so much you can do with cast). Cases were fully Blueprinted by famous tool & die maker and racer "Sir Eddy" and we found significant anomolies on the cases... crank bearing bores was out a lot towards 7 oclock, and cam centerlines were off and out towards 4 oclock, Once trued up stock 650 top end, 1971 cyl head, and a 357 SRM camshaft. Capt Dirt (Jim) told me "Aint nuttin' wrong with the BSA top end, they breath better than Triumphs and the cams are great"

Now, I dont think that combo would be fun in a touring or daily rider street bike,, but in a lightweight chassis it was a rocket. The guy I built it for said it revved like a 2 stroke and with the CR box it kept it in a nice Power band thru the gears. He brought it back a year or so later and I took it up and down the road and it DID indeed just haul ass. But It would be a handful and not very fun as a daily rider.

Re: How many A70s did BSA produce? [Re: kurt fischer] #735574
05/16/18 8:51 pm
05/16/18 8:51 pm
Joined: Aug 2005
Posts: 1,322
melbourne florida
B
bodine031 Offline
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Posts: 1,322
melbourne florida

Re: How many A70s did BSA produce? [Re: kurt fischer] #735581
05/16/18 9:33 pm
05/16/18 9:33 pm
Joined: Oct 2006
Posts: 2,537
Elburn, Ill. USA
I
Irish Swede Offline
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Irish Swede  Offline
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Joined: Oct 2006
Posts: 2,537
Elburn, Ill. USA
Sluggo, you are correct about the '66 and early '67 Triumph 650 flywheels. Triumph wanted the "high performance" image at that time and installed "chopped" flywheels to create quick-revving engines.
Problem was; they were "high-VIBRATION" engines as well.

The bikes would shake nuts off of bolts, make bolts disappear, shed parts, and crack sheet metal components.
Guys in my area would buy tubes of 3-M yellow weatherstrip cement to glue the nuts to the bolts. not unusual to a '66 Bonneville, with gobs of the stuff on all the fasteners. We called it "The Yellow Peril."

By late '67 or 1968 Triumph returned to heavier, smoother-running flywheels, with little loss of performance, and much more riding pleasure.

You found a way to use those lightened flywheels. Good for you!

Re: How many A70s did BSA produce? [Re: Irish Swede] #735587
05/16/18 10:22 pm
05/16/18 10:22 pm
Joined: May 2018
Posts: 64
Oregon, USA
S
Sluggo650PNW Offline
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Sluggo650PNW  Offline
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S
Joined: May 2018
Posts: 64
Oregon, USA
Irish Swede, those were not the ONLY Triumphs to have that problem!!! The Duplex twins (60-62) had issues. Cliff "Sandy Bandit" Mahjor had an interesting take on them. (I wish had recorded his tales on video, what a character!) The Duplex preunits shook like crazy and were a serious issue for the dealers, Cliff had a crazy method of where the flywheel came to rest and would drill holes in it thru the bottom sump plate, test ride and drill more. After a while he knew exactly how and where to drill and claimed he fixed all that came thru his shop.

I of course do not recommend this. By Dynamic balancing guy does Airplane propellers and industrial machinery mostly and does the Motorcycle stuff because its fun and interesting.
I have found *MOST* Triumphs dont have too many issues on balancing, (Nortons are the worst in this dept, but quite enjoyable when sorted). But I did have a customers 68 Bonnie that shook excessively. I still have the rods and they were starting to crack which is unusual on a Trumpet, We replaced the rods, Did the usual Blueprinting and Dynamic balanced it and it
came out very smooth.

I have a early 66 T120C and a mid 66 T120R awaiting restoration sitting here, Parts ordered and time to build them, will start in the fall after the Norton rally and some other events.
I got the T120C as a runner, although Bobbed and rode it like that for a few years, To upset some of the locals I kept telling them how I was going to make it into a full on chopper,,:)
And It wasnt too bad shaking,, bigger issue was the ET ignition and lack of lighting when you let off the throttle, which can get exciting on the hills around my place.
(Pull in clutch, rev motor, line up your path down the road, Engage clutch again), I submit a lighter crank smooths out the ride a lot, And for a rider and touring its the way too go,,
So, lightened cranks are more for the race crowd, But IMHO the key is blue printing and the Dynamic balancing. For an extra $10.00 my guy will also do your alternator rotor and many overlook how much that can impact vibration. Huge amount of weight leveraged on the end of a crank, and out of balance can exert considerable mayhem. I found the clutch baskets dont cause much issue but we have done them too. Cam wheels are just over the top and no one will notice the difference on them, but *IF* you are OCD enough its done sometimes.

But its surprising the alternator rotors, Some come back with a few dimples to get balanced, some look like swiss provolone. Back to OP topic, I would love to have some time examining the NOS BSA pistons. Weights, measurements etc. The asian made cycle crafts,, now called JCC or EMGO are remarkable consistent both with measurements and weights,, The piston pins supplied tend to vary in weight, but the pistons are so consistent except for one set we got, That I used to take multiple cyls to the machine shop and only one set of pistons
and didnt worry about sizing. Bore them all to this size. But OEM pistons, Wellworthy, Hepolite and the like can vary by several grams and thousandths of an inch. Those you true up as much as possible but need to be matched and carefully machine the bores to suit.

If someone HAS access to some A70 Pistons, would it be too much to ask to weigh them? Pins separately and rings OFF. Then mic them too. Please?? Please? Pretty Please?? Pictures would be awesome as well.

Re: How many A70s did BSA produce? [Re: Sluggo650PNW] #735878
05/20/18 4:04 am
05/20/18 4:04 am
Joined: Oct 2001
Posts: 1,129
Sydney, Oz
S
Shane in Oz Offline
BritBike Forum member
Shane in Oz  Offline
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S
Joined: Oct 2001
Posts: 1,129
Sydney, Oz
Originally Posted by Sluggo650PNW
Need a flywheel for one? I have some old warehouse NOS stock still in the wrapping, Some accounts have way more spares than bikes produced, I dont know for sure but several ex dealers told me that.

I could do with one of the flywheels.

It makes sense that BSA produced a lot of spares for the A70s.
  • they were intended for racing, so
  • - would have been rebuilt on a regular basis
  • - race teams tend to have at least 1 spare engine
  • some of the parts (e.g. pistons, main bearings & shims) were bought in, so BSA would need to buy a minimum order batch
  • the con. rods were also used on late A65s
  • the A70L was almost certainly intended as a production model for the 1973 model year, like the T140

Re: How many A70s did BSA produce? [Re: kurt fischer] #736123
05/21/18 10:35 pm
05/21/18 10:35 pm
Joined: Jan 2014
Posts: 3,753
Aus
N
NickL Offline
BritBike Forum member
NickL  Offline
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N
Joined: Jan 2014
Posts: 3,753
Aus
There were loads of engines and parts about, some legitimate, some out of the back door, heaps of sidecar racers in the UK were using them.
Despite the A70 never being sold in the UK. The Birmingham Mafia was at it's height in the early '70's



Re: How many A70s did BSA produce? [Re: kurt fischer] #736204
05/22/18 4:05 pm
05/22/18 4:05 pm
Joined: Dec 2003
Posts: 114
Pittsburgh,Pa.
R
Redd32 Offline
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Redd32  Offline
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R
Joined: Dec 2003
Posts: 114
Pittsburgh,Pa.
The A-70 timing side bushing is narrow compared to early A-65. Also it had a big hardened washer to control end play. The timing side engine case is spot faced for the narrow bushing and washer. I believe the A-70 crankshaft timing side journal might be narrow also.

Re: How many A70s did BSA produce? [Re: kurt fischer] #736349
05/23/18 8:47 pm
05/23/18 8:47 pm
Joined: Dec 2005
Posts: 548
Kansas City area
BritTwit Online content

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BritTwit  Online Content

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Posts: 548
Kansas City area
Of the 200 built, only 386 are known to still exist.

Re: How many A70s did BSA produce? [Re: kurt fischer] #736353
05/23/18 9:15 pm
05/23/18 9:15 pm
Joined: Jun 2013
Posts: 237
Georgia Mountains
G
goodtry Offline
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goodtry  Offline
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G
Joined: Jun 2013
Posts: 237
Georgia Mountains
I have one if someone wants to purchase!

Re: How many A70s did BSA produce? [Re: kurt fischer] #736361
05/23/18 10:12 pm
05/23/18 10:12 pm
Joined: Jan 2014
Posts: 3,753
Aus
N
NickL Offline
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NickL  Offline
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N
Joined: Jan 2014
Posts: 3,753
Aus
Number 387?

That would be rarer than the 4800 RGS's that are about eh? or the 6000+ Thruxton bonney's



Re: How many A70s did BSA produce? [Re: NickL] #736422
05/24/18 12:17 pm
05/24/18 12:17 pm
Joined: May 2013
Posts: 4,828
Rotherham - S. Yorkshire
Allan Gill Offline

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Allan Gill  Offline

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Joined: May 2013
Posts: 4,828
Rotherham - S. Yorkshire
Originally Posted by NickL
Number 387?

That would be rarer than the 4800 RGS's that are about eh? or the 6000+ Thruxton bonney's



Its a growing number Nick, the A70 still has another 10+ years of age before the official original bikes reach nearly 5000 grin


beerchug

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