Why The 1970 BSA A65 Is The Best Year
There are still many opinions today of which BSA A65 that was produced is deemed to be the "best" year. It appears today that everyone automatically believes that they have the best year A65 simply because they own it.
Brief History
Artwork of a BSA A65 unit twin engine - pulled from a period magazine article
Frame
BSA A65 "dry frame" blue print
Probably one of the best features for the 1970 was the "dry" frame. Just the next year in 1971 (also carried on in 1972) BSA designed and produced a new frame in which the oil was located in the center frame down-tube. Also known as the "oil in frame".
The oil in frame design ultimately put the nail in the coffin for the BSA motorcycle company and severely hurt Triumph during the fallout. BSA had control, influence, and power over Triumph at that time as BSA owned Triumph. Many are not aware that the Triumph oil in frame was designed by BSA.
There are many opinions on the oil in frame models. From a value point of view prices typically drop for BSA and Triumph models from 1971 and on due to the oil in frame design. Although the oil frame models handle very well they are not appealing and they also have there flaws.
Horns
Just like the 1970 Triumph Bonneville the BSA lightning was the only model for 1970 that featured dual horns. For those that are familiar with the dual horns they are called Clear Hooter horns which today are extremely difficult and hard to locate.
Although the 1970 BSA Lightning featured dual horns not all came equipped with them from the factory. Many where fitted with 1 single horn or dual "thunderbolt" horns which where different in style, shape, and sound.
Lightnings that came equipped with dual horns had a special head stay bracket in which one could fasten the Lucas 6RA horn relay for the dual horns.
Base Studs
3/8" diameter base studs along with 3/8" size 12-point base nuts
The cylinder base studs in 1970 where changed from the smaller 5/16" diameter to the larger 3/8" diameter. It only took BSA 7 years to make this change - should of been implemented sooner.
The larger diameter base studs allowed a higher torque rating on the cylinder barrel. I heard of one instance in which a cylinder barrel lifted from the crankcase on an early model that had 5/16" studs... according to John Healy.
The 3/8" base nuts where also changed from standard hex to the new 12 point nuts to allow easier adjusting when using a box end wrench.
Cylinder Barrel
Cylinder barrel fin cutouts as seen on this 1970 BSA A65
Never seen before until the 1970 - A65 models where now fitted with cylinder barrels that featured cutouts above the cylinder base nuts. This change was also carried through 1972.
This new change allowed easier access for a box end wrench to slip over the base nuts. Previous years did not feature this design which made it more challenging to slip a wrench between the base of the barrel and over the nut.
Late barrels from 1970-1972 are getting harder to find today as they where only used for 3 years. They are not interchangeable with early models as they are suited (and offset) for the 3/8" diameter base studs.
Stud Pattern
We now know that in 1970 BSA A65s now had the larger 3/8" base studs. Although the design is similar to that of the 5/16" studs, cases with 3/8" studs have an offset pattern.
Clutch
New clutch set-up on the 1970 BSA A65 - very similar to Triumph twins
The new clutch actuator allows a much smoother feel on the clutch lever for a more positive clutch release.
Notice that the outer timing cover has been changed as well. Inspection plug and an extra fastening screw - new for 1970.
Coils
Smaller Lucas 40MM diameter coils and bracket - new for 1970
Normally 48MM Lucas coils where fitted to A65 models - 1970 A65's where fitted with smaller 40MM coils as usually found on most Triumph and Norton models. I am not exactly sure why this change was implemented. I can only assume that perhaps the large Lucas coils where not available or where to expensive.
The coil bracket to house the smaller Lucas coils where also changed making them a "one year only" part. 40MM coils and brackets are listed in the 1970 BSA 650 parts book only.
Mirror Holes
Mirror holes on both the clutch and brake perch - new for 1970
Mirror holes on both the clutch and brake lever perch was a new design for 1970 models. Most laws in the USA (depending on the state) require to have at least (1) mirror on either the clutch or brake side. Mirror holes shown above accept an 8mm threaded mirror.
Earlier BSA models prior to 1970 did not feature this clutch and brake lever perch design. To adapt a mirror you would have to use the "clamp-on" style mirrors.
Conclusion
If you're familiar with early BSA A65 models I'm sure that you can come to the conclusion and agree with me that the 1970 BSA A65 is the best year based off of this information and experience.
From a buying, selling, and an investment point of view I personally feel that all 1970 BSA A65 models are the best choice. 1970 models retain there value better than any other year (except rare models) especially the 1970 BSA Lightning.
So there you have it - my 2 cents on why the 1970 BSA A65 is the best choice. If there is any information that I missed or did not touch on, please let me know by commenting below. I would appracite everyone to chime in using the section below. As always, thank you for reading today's blog post.
Ron Winget
I love my ‘70 T-bolt! I don’t say that lightly. I am a big fan of the British bikes and have owned Triumph, Norton, and BSA. They all give a thrill when in good tune, but the ’70 A65 is the easiest to ride, most reliable, and still great looking. I did spin the timing-side bush after 20K miles, but it has given me an opportunity to improve the bottom end. I think I can get another 20K out of it!
Scott Dundas
BSA never produced a 650 twin with a timing side ball or roller bearing. The drive side has a ball bearing.The timing side was always a plain bush that needs to be set up with the correct amount of end float. This has always been a weak point in the BSA twin range from pre-unit to the last of the OIF models in 1972. Even the A70 was built with a timing side bush. BSA new it was an issue but never did anything about it. In later years they did put needle roller bearings in the timing side of a limited number of factory race bikes . When BSA closed the head of their race department set up a U.K. Company called Devimead and they offered a conversion that replaced the timing side bush with a needle roller bearing. This is still available today through a company called SRM in the U.K. I understand that SRM bought out Devimead many years ago. They have a range of trick BSA parts.
Chris Horwath
I read somewhere that after 1965 BSA replaced a bearing with a bushing on the crank. The bushing on some bikes would would slide and cut off oil supply which caused catastrophic failure.
Took years to figure this out and meanwhile they tried to get better top-end cooling by the finned head cover. BSA was guessing at the time as to what was the issue on some bikes. Now the post-65 bikes need to be shimmed to prevent this. So to me the 1965 or earlier with the bearing are better. I also like the look of the smooth cover. LOL!
Stephen C Dapson
Was is only the 1972 Models of the A65 that had wider gasket surfaces for better oil retention?
tony norskog
good article, I have a 69 and will have to drag the computer down to the bike to compare.
FYI, you need someone to proof read for spelling, there and their, to and too have very different meanings.
cheers,