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#832692 12/09/20 4:01 am
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Where in the USA can I have the crank and cases of my 1969 BSA 650 Thunderbolt modified with the upgraded right side main bearing for competition use? I am wanting to supercharge the bike.

JVRJR

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E&V Engineering, Howard city Michigan...

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Originally Posted by jvrjr
I am wanting to supercharge the bike.

JVRJR


I hope the following doesn’t mind me promoting them here, but PushRodTom has done some amazing things with A65’s, as has Mark Parker and Nick L.

PRT has a supercharged A65, goes at a fantastic speed. But if you want some advice, these guys know a lot.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

jvrjr #832718 12/09/20 12:50 pm
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Sounds like a good project! My own turbo motor still has the original crank and bushing that came out of Birmingham in 1966! With #50 oil it has 50# pressure and just keeps going along. I know it sounds weird but it has been raced since 2009 and has many speed passes over 150. Hope this helps you decide what to do. PRT

PS I feel that the crank flexes a fair amount at elevated power and rpm levels so, if that is your goal I would set bushing clearance at .003 or a hair over. If you are talking about a street bike then, maybe, .0025.

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Originally Posted by pushrod tom
Sounds like a good project! My own turbo motor still has the original crank and bushing that came out of Birmingham in 1966! With #50 oil it has 50# pressure and just keeps going along. I know it sounds weird but it has been raced since 2009 and has many speed passes over 150. Hope this helps you decide what to do. PRT

PS I feel that the crank flexes a fair amount at elevated power and rpm levels so, if that is your goal I would set bushing clearance at .003 or a hair over. If you are talking about a street bike then, maybe, .0025.
I have see Tom's run and it does the job ...
Tom, I have to ask, does the famous Ak Miller statement apply? " if turbocharging you have tried, threre are pistons you have fried"


grin


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
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You need a centre main bearing on the crank. A needle bearing is not going to last with a lot of angular misalignment caused by crank flexing.

jvrjr #832779 12/09/20 11:05 pm
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Thanks everyone for the info. I would also like to fit a 5 speed trans. Is that possible? I've been road and LSR racing since 1967. Except for a Yamaha SR/XT500 special I have never raced a 4-stroke. All my racers were TD/TZ 125,250,350 and 750 Yamaha 2-strokes. I previously owned a BSA 442 Victor and a 750 Norton Commando years ago in the '80s. I got the BSA in 2012 when a guy brought it into my shop with 5600 miles on it. Mechanically it is original except for new rings and valve job. The bike was found in a shed outside Redlands, Ca in the desert. It had been sitting there since 1973. The tank and pipes needed replacing when I got it. I replaced the US tank with a new home market style 4 gallon tank. The tank and side covers have been repainted the original dark metallic red and re-striped in gold with tank new badges and side cover decals. It is my daily ride, always starts on the 2nd kick and I love it.

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jvrjr #832788 12/10/20 12:48 am
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Best way to stiffen/strengthen the crank is to offset it.
Makes for a better engine too.

What class of racing are you going into?




BTW, don't believe a word of what Allan says about me, i've blown too many up to be any good.

Last edited by NickL; 12/10/20 7:26 am.
jvrjr #832820 12/10/20 12:29 pm
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Tony, Yes, There are fried pistons as well as valves, gaskets and rings. Mostly when pushing the button. We feel that we have a better handle on the nitrous situation and are looking forward to having a chance this coming year. PRT

PS, How is the A-10 coming along? I have really enjoyed mine over the years and even treated it to a new tire this year! 1958 full body, fenders Flash.

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If I race the bike I plan on running with the AMA Bonneville Motorcycle Speed Trials. I would run in the classic, pushrod, supercharged fuel and gas classes unstreamlined.

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Forgot to ask how is the crank offset? Seems it would be quite a complicated modification.

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Originally Posted by pushrod tom
Tony, Yes, There are fried pistons as well as valves, gaskets and rings. Mostly when pushing the button. We feel that we have a better handle on the nitrous situation and are looking forward to having a chance this coming year. PRT

PS, How is the A-10 coming along? I have really enjoyed mine over the years and even treated it to a new tire this year! 1958 full body, fenders Flash.
The A10 engine parts, crank, cylinders, new pistons and head is at the machine shop.. There are a few issues but I trust the shop ....The frame is a roller...I believe the bike will look like a bike in a month..


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
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If you mean offset being 90/270 big end spacing instead of 180/180, then it will cause a lot of problems for a supercharged engine. You would struggle to get even cylinder filling.
If you mean offset being "desaxe" where the cylinder centre line is offset from the crank centre line, this will reduce piston to bore pressure (and friction) during the power stroke


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jvrjr #832892 12/11/20 12:13 am
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A 90 degree crank lessens the dynamic load by about 40 percent from what I've read. It should be like adding strength. At the std stroke as a big bore 744 it can be quite smooth as well.

Supercharging in my view wouldn't be as much fun as normal asperated. Because to do so can lead to vast modifications and get a long way from the basic engine and also into lots of expense. I guess it depends on what you want though.

The basic engine has a lot of room for development and tuning. Especially the head which is so close but not ported correctly standard. The Thunderbolt head can flow just as well as a Lightning head ported with the same size twin carbs and valves. Blowing a stock head is probably restricted without re-forming the port shape.

There is an expectation associated with blowing or large displacement. Having a small displacement performing unexpectantly well can be very impressive, even if speeds were a bit slower.


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Andy, the bike would have to use 2 carbs or otherwise as you say blowing it
would present problems. Indeed it does when normally aspirated with an offset crank.
Moving the barrel or crank forward and backwards is getting into the realms of complication.....
Fitting pistons with offset pins may be a good idea though, MCS used to make such forged
ones years ago for a65's. Good for methanol too, i'm told, though i've never tried them myself.

Super Nero by George Brown used a single carb blower on the v twin vinnie quite successfully though.
I think it was one of the old 'cabin blowers' out of a high altitude spitfire, a few blokes used them.
https://www.bikeexif.com/vincent-motorcycle-2

Last edited by NickL; 12/11/20 3:44 am.
jvrjr #832929 12/11/20 10:58 am
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My friend Tim in the UK uses a blown A65 in a drag bike. He makes lots of good stuff for it. He puts a pin in the crank.


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Originally Posted by Mark Parker
My friend Tim in the UK uses a blown A65 in a drag bike. He makes lots of good stuff for it. He puts a pin in the crank.

Would that be Tim Howell?


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
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jvrjr,
If you plan to run the bike at Bonneville, BMST or SCTA, remember that the A65 is actually 654cc and cannot run in the 650 class unless you de-bore it or de-stroke it. It will be measured if you set a record and cannot exceed 650cc. You can of course run it in the 750 class.
Tom


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Originally Posted by koncretekid
jvrjr,
If you plan to run the bike at Bonneville, BMST or SCTA, remember that the A65 is actually 654cc and cannot run in the 650 class unless you de-bore it or de-stroke it. It will be measured if you set a record and cannot exceed 650cc. You can of course run it in the 750 class.
Tom

The 654 cc would come up for discussion at Loring and the Ohio track among the Triumph guys..We did not think it really mattered considering you're allowed .020 oversize pistons . So for instance a 649 cc engine goes over 650...That's how I understand it...But... rules are just that and the line has to be drawn at some point.


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
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80X74 and 744cc are probably the optimum size.

Yes Andy Tim Howell.


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Good point OT. My turbo is 74.5x74 and the NA bike 70.5x76.5. Just in case we ever make it to the salt........... PRT

jvrjr #838367 01/28/21 10:26 pm
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Back the original poster jvrjr's question about getting a needle bearing conversion for an A65--I had mine done by Frank Deihl's Classic Cycle Works in Georgetown, SC. http://www.franksclassiccycle.com/ Frank is a delightful fellow to talk to, free with his advice, is very fair on pricing and does great work, and he has put up some informative Youtube videos --take a look at this for an overview of his shop, if you are interested in seeing a big and successful vintage bike shop.
I went to Frank for my A65 crank conversion because he was highly recommended, along with E&V, by someone who was very informed on the subject, and because Frank could commit to do it sooner than Ed Valkett--no knock on Ed here at all.

Interestingly, in the mid 70's when I was in DC and racing motocross, Frank was the parts and accessories manager for Heyser's Cycle in Laurel MD, and I raced a CZ out of the rival Dirt Shop in Beltsville MD, just down Highway 1. Heyser's fielded some of the first 1974 YZs, both the very trick short travel YZ 250A, and the uber trick first year Monoshock, both of those with the silver gas tank held on by a belt. http://www.owencollection.com/collection/bikes-from-the-70s/1974-2/1974-yamaha-yz-a/ Those things were so trick and light, compared to old school European bikes! In comparison to them, my CZ looked like a Fordson tractor, LOL. And, I raced at Daytona in 2005 on my Triumph when Frank and Heyser ran their ABSAF Gold Star that won so many races that year, too.
Anyway, it's a small world out there, the world of motorcycles, which I am reminded of again when I run across someone I first enountered nearly 50 years ago, fixing my BSA now. Cool.

Last edited by linker48x; 01/28/21 10:50 pm.

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