1972 BSA B50 mx engine for sale "Race built"

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Frank Davis
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1972 BSA B50 mx engine for sale "Race built"

Postby Frank Davis » Thu Jul 30, 2015 6:18 am

This is a 1971 BSA mx 500cc single engine only....we used to call these "thumpers"....Only this engine is special, it was built and raced by the motor builder "wizard" John A. Miller....John raced motorcycles in the 50's and graduated to building Grand Prix and Indy car (winner) engines for Dan Gurney and Bobby Unser (among others) before starting his own elite shop in Hawaii....This was his latest personal competition engine and was freshened up before going into mothballs years ago....flash into the future...John sadly passed away in 2014 and I purchased this from his widow....It is sitting on a stand he built for his beloved BSA engines.....the last photo is of John and Dan Gurney going over a flow test.
I have decided (after many questions) to open up the top end for inspection and photos...everything looks new and beautiful.....here are some photos....I am not sure of the piston markings though....a rough bore measurement was 3.488" or so and the stroke approx 3.5".....alloy pushrods, and nice valve job.....don't think I am going to open up the bottom end, I think the top end work shows the quality of build I should expect to see in the lower....the only component not installed when the engine arrived is the stator assembly.....kicker and shifter are installed, but not pictured...This engine will need re-assembling after inspection.
I pulled the barrel..again, very nice ...looks like John Miller installed a Carrilo con rod... piston id (Mahle, porsche)...obviously, not stock...and has his initials with JAM (John A Miller) on con rod and all major components....flywheels look polished too....this is as far as I go.....more photos on request....asking price is 1500 usd....FOB Myrtle Creek, Oregon USA.
Attachments
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001.JPG
Dan Gurney and John A Miller at the flow bench
john miller dan gurney.jpg
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003.JPG
006.JPG
002.JPG
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Last edited by Frank Davis on Thu Jul 30, 2015 5:58 pm, edited 1 time in total.

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HPbyStan
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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby HPbyStan » Thu Jul 30, 2015 4:45 pm

Does the cylinder have a cast iron liner ? I remember when Gurney & Palmgren made a B50 for AMA Flattrack racing they used a stock Porsche 911 piston with a Carrillo con rod with a 23mm piston pin hole like the ones in your picture and they machined all the fins off the Porsche cylinder and pressed what was left into the B50 cylinder so the Porsche ring package would be running on a surface it was designed for.

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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby Frank Davis » Thu Jul 30, 2015 4:45 pm

I have no problem shipping International, but it could be costly...a prospective buyer may want to explore a re-shipper for this....I will crate this motor for the cost of materials....Thanks, Frank.

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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby Frank Davis » Thu Jul 30, 2015 5:48 pm

HPbyStan......here is another photo showing the liner....I believe you are correct on the liner of this engine...Thanks, Frank
Attachments
001.JPG
003.JPG

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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby HPbyStan » Thu Jul 30, 2015 6:21 pm

3.464" = 88mm
3.543" = 90mm
88mmB X 90mmS = 547.4cc
Not sure what you have for a cylinder liner except it probably isn't B50. No fire ring at the top and dowels / sleeves added to locate the head to the cylinder. IF, it's cast iron it might just be a big bore BSA liner with the fire ring machined off because of the larger bore. 84mmB X 90mmS is stock.

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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby Frank Davis » Thu Jul 30, 2015 6:37 pm

not mentioned yet...14 tooth drive sprocket

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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby HPbyStan » Thu Jul 30, 2015 8:32 pm

Just for grins,,,
Image
911 85mm piston
B50 cylinder and rocker box and 911 head. Even most of the B50 rocketbox studs and 911 OHC cambox studs are even in the same place
Image
Image
Somebody copied somebody. Valves, valve angle, combustion shape are identical.

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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby Frank Davis » Sat Aug 01, 2015 12:55 am

Thank You Stan for all the help and input....and for the referal to Chuck Palmgren at All-American Racing for further information on this motor.

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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby Frank Davis » Mon Aug 03, 2015 6:21 am

This engine has been sold and is no longer available....Thank you for your interest......Frank

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Re: 1972 BSA B50 mx engine for sale "Race built"

Postby HPbyStan » Mon Aug 03, 2015 3:39 pm

Frank Davis wrote:Thank You Stan for all the help and input....and for the referal to Chuck Palmgren at All-American Racing for further information on this motor.

Welcome Frank and I enjoyed talking with you... Stan


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