Author Topic: Four cylinder A7  (Read 137 times)

Online Greybeard

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Four cylinder A7
« on: 01.07. 2019 19:28 »
Coil ignition Austin Seven, (A7) engine fitted to a BSA frame.
My 1929 Austin 7 had the same engine. The distributor is mounted on the end of the dynamo. On this bike the starting handle 'nose' has been cut off and capped. The pulley for the fan belt has been removed. I assume an electric fan has been added behind the rad. The engines didn't have a water pump, relying on thermal circulation. I'd like to see the flywheel end of the bike to see how the primary was connected.

Online duTch

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Re: Four cylinder A7
« Reply #1 on: 01.07. 2019 23:12 »
 Interesting, but metinks not an A7 frame based on the tranny- must be from a single, and it mounted behind the frame downtube *conf2*

 Based on the engine, I guess it can be called an A7
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online Greybeard

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Re: Four cylinder A7
« Reply #2 on: 01.07. 2019 23:16 »

 Interesting, but metinks not an A7 frame based on the tranny- must be from a single, and it mounted behind the frame downtube *conf2*
No, I think it's a B series frame. A7 came from the Austin 7 engine.

Online ironhead

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Re: Four cylinder A7
« Reply #3 on: 02.07. 2019 05:13 »
I recon that's an M series frame. Bottom frame tubes go through to the bottom of the front down tube.
SA

Online Triton Thrasher

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Re: Four cylinder A7
« Reply #4 on: 02.07. 2019 07:21 »
Looks like a Triumph gearbox.  Don’t think its got any cooling fan.


Good enough for Brough, anyway:


Online Greybeard

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Re: Four cylinder A7
« Reply #5 on: 02.07. 2019 12:51 »
I've seen one of the Brough Austin Seven jobs at the National Motorcycle Museum. Note the twin rear wheels.

Offline cyclobutch

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Re: Four cylinder A7
« Reply #6 on: 02.07. 2019 13:00 »
So is that just a twin main bearing engine in those?
Various, including ...
'58 Iron Head Flash Bitza


Online Greybeard

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Re: Four cylinder A7
« Reply #7 on: 02.07. 2019 13:02 »
So is that just a twin main bearing engine in those?
Mine was. After about 1931 they went to three bearings.

Offline cyclobutch

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Re: Four cylinder A7
« Reply #8 on: 02.07. 2019 14:06 »
Mine was. After about 1931 they went to three bearings.

Keeps the block very short, but I don't know how much tune you can put through them. My Nimbus is like that, and I've seen one being prepped for the salt flats.

https://www.autoevolution.com/news/odin-s-fury-the-nimbus-to-tackle-the-bonneville-salt-flats-video-97610.html
Various, including ...
'58 Iron Head Flash Bitza


Online Greybeard

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Re: Four cylinder A7
« Reply #9 on: 02.07. 2019 14:32 »
Mine was. After about 1931 they went to three bearings.

Keeps the block very short, but I don't know how much tune you can put through them. My Nimbus is like that, and I've seen one being prepped for the salt flats.

https://www.autoevolution.com/news/odin-s-fury-the-nimbus-to-tackle-the-bonneville-salt-flats-video-97610.html
Tuned Austin Seven racers achieved 100mph at Brookland with a two bearing crank. It was said that at high revs the middle two pistons would hit the cylinder head because of crankshaft whip. The big-end diameter on early engines, mine included was 1 1/8".

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