Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board The A70 Lightning story (rebuild)

I don't usually post progress stories on my rebuilds because I am so slow. When this one arrives I will assess the condition and decide what to do. If the bike cleans up pretty well and looks half decent I will assemble the engine and get the bike on the street for a while. Then maybe do a complete restoration. I am moving the photos over from the garage sale to show the starting point for the build

and a couple more

You got a really good deal there with that bike, I was one of the interested parties and was prepared to offer a lot more for it.

Good luck with the rebuild and probably restoration. Being one of the last A70s ( i think) that left the factory and being so few in the first place of a rare model it would be a real shame not to restore it to its former glory.

Best regards

A total restoration is the goal. I find if I can ride it around for a while it helps me concentrate on completing the restoration.

Bookmarking this thread, can’t wait to see this one come together in whichever form you choose

I agree. I've never come so close to doing something stupid and adding to a collection of planned projects that I would probably never complete in my lifetime as I did in considering buying this bike.

Glad it's going to come back to life. We're not in a hurry, but if the fact that people are watching helps motivate you into working on it, then that's a healthy thing!

Lannis

bsalloyd - Is that the A70's crank?

Mine looks so much different than yours. The flywheel has been seriously lightened. Supposedly factory done.

All a70 and last of the A65 were like that. The width of the scalloping differs between the 650 and 750.

IDK - Something looks different Allan. Mystery...

The width on the late A65s between the scalloping is 40mm. When I converted an A10 crank for my A70, I estimated that the width was 35mm from the attached photo I saw on one of the forums.
A65 on left, A70 on the right.
Good luck with the rebuild, I'll watch your progress with interest.

Nice find! I look forward to seeing it once it's together.
I always had one question about the A70. The pictures I've seen show it as having a triple oil cooler. I never measured over 170 degrees oil temperature on my A65 with a tiny chopper oil cooler. Do these bike really run that hot or was it just that they were only designed for flat track racing?

The OIF was a little low on oil capacity and not the best for oil cooling at constant 6-7500rpm
I don't know how long the flat track races were but when those lumps were/are 'pepped up' they
could produce 70bhp. so a cooler wasn't a bad idea.

Sorry I can not answer many questions about this bike. It is the first unit construction type I have overhauled. I should know more after I complete it.

According to what I have found it was the tenth bike to come off the line in June 1971. I will still send the details to the BSA owner club for dating.

Races were usually 25 laps.Not sure is that applied to all TT, short track, half mile and mile.
Dave Aldana's bike does not have a cooler but Jim Rice's does, from 1971

Trackmaster frames had a smaller backbone than OIF's but the fill was at the headstock.
This is a Tri-C Trackmaster frame which has a sheet metal extension to the top backbone for more oil. Not sure if the original Trackmaster had this.

The bike arrived at my home 4/18/23 at 5:00 AM. I will post pics once I get everthing unboxed

Two photos of the bike after the sun came up

I thought you said you were slow with your rebuilds.

I bet it's an inventory build to see what's missing. But it looks mostly all there.

I like my story better

There don't seem to be many obvious parts missing, so I'm looking forward to the blow by blow rebuild, with lots of pictures.

Could just be bad lighting on those first pics.

It looks like I could just drive away on it, but that is nut the case. So, tear down is coming.

Agreed, No chain, kicker, shifter or spindle, clutch cable and probably no guts in the engine.

It is the small details that cause the issues

Fortunately, most parts are the same as the A65.

It's the unique parts which will cause the most delays if any are missing or worn.

Do you have the A70L pages for the 1972 parts book? I can scan them if you need them.