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#867974 01/03/22 1:24 pm
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Well, with the unusually warm weekend I was able to get the 72 BSA LSR up on the lift to start the rear wheel/ drum brake conversion to a Disc Setup. Will need to fab up some mounts and such for the master cylinder attachment and will add photos long the way. AS soon as this conversion to Disc Setup is completed I will be moving on to double checking the top end prior to start up and dyno tuning for racing this summer at Loring. Mat even finally get a chance to fabricate a streamline front fender too.

LSR3.jpg LSR4.jpg LSR5.jpg

1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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Are you trying one of Mark Parkers ported heads this year ? Or am I mistaken .


1968 BSA Firebird
1200 Sportster
XS 1100
1972 Rickman 125
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Originally Posted by konon
Are you trying one of Mark Parkers ported heads this year ? Or am I mistaken .
Yes, and with the flow numbers Mark achieved this should really increase the performance numbers. On the stock 1972 head the bike had 60hp and 60ft.lb/tq. I wouldn't be surprised if I need to get larger carbs too from the 34mm flat slides I currently have fitted.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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Lookin good Chris! Hope to get there myself. Both bikes need serious work to have a chance to move forward.

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This conversation takes me back to the days when I was feverishly following American racing, and was absolutely amazed that Jim Rice, among others, was winning races and competing for Grand National championships on a 650 BSA twin as late as 1972, competing against Harleys, more advanced Yamahas, Nortons, BSA triples, and other bikes that "should" have left an A50-A65-based bike in the dust.

What kinds of things did Jim do to his motors to make them competitive with the other 60-horsepower racers out there? Do you guys do the same things to your race motors? Are there new technologies, materials, ideas, etc today to help pump these motors up?

Lannis


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I think 34s are what you need Chris. Hopefully it will have lots of power before or around 7,000-7,500. That size carb seems to work as you have speed combined with volume which should give it good punch. It's interesting on the 650 because it makes a really fun responsive street engine that seems to have a pretty big hit when opened right up. Even with just 9-1. I think it may be the speed volume thing, some graphs would be interesting, this uses std '70 Firebird headers and an H connector that may be a little bigger, I made it because I didn't have one. I don't know what might be best on the LSR bike, it might be you get strong midrange with best hp in that rpm range with the best pipe set up.


mark
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Can't really speak to BSA's, Lannis. And my racebike isn't doing 60hp (although horsepower numbers are only a tool used in the dyno/ tuning process. Instead of 60, you could say 12 and if you wound up at 13 you'd be successful. Unless you're talking about the 170hp harley but thats another story.)
Aside from a more modern piston design, we're still using the basic formula laid out 50+ years ago. Cams, porting, exhaust, ignition- old school hot rodding. It comes down to careful assembly and attention to detail on the nuts and bolts and hard parts.
I suppose when you get to that 70hp and up range, things are exponentially different.

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Originally Posted by Lannis
This conversation takes me back to the days when I was feverishly following American racing, and was absolutely amazed that Jim Rice, among others, was winning races and competing for Grand National championships on a 650 BSA twin as late as 1972, competing against Harleys, more advanced Yamahas, Nortons, BSA triples, and other bikes that "should" have left an A50-A65-based bike in the dust.

What kinds of things did Jim do to his motors to make them competitive with the other 60-horsepower racers out there? Do you guys do the same things to your race motors? Are there new technologies, materials, ideas, etc today to help pump these motors up?

Lannis
Lannis,

Like Mike mentions above, Cams, porting, exhaust, electronic ignitions, high compression and racing fuels are basically all I do along with meticulous attention to detail during assembly. . My option is the BSA A65 has a better stock combustion chamber than say HD's, Norton's and even Triumphs.

Haven't gotten anything done the past couple days as I have been digging out from our 14" of wet snow received on Monday. Hoping to have some work moving towards the weekend.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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Thanks Tom. Hoping to have her ready for some much needed and anticipated dyno tuning by end of March at the latest. Was hoping Mike would be able to fit me around that time.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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Mike and I will be looking forward to a good workout!

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chris even if your machine blows up it will always win tbe award for being the most beautiful bike at the races.


i'm old enough to remember when patriotism meant not trying to overthrow the government.
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Originally Posted by kevin
chris even if your machine blows up it will always win tbe award for being the most beautiful bike at the races.
Thanks Kevin! I hope I dont encounter any blow ups but you never really know when your trying to push an engine to its max.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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Was able to get some more work done on the disc brake conversion this past weekend. Got the wheel mounted, shimmed and sprockets aligned, just need to readjust spokes now to align the wheel/ tyre so its aligned with the front wheel. The only left on the caliper/ disc side is to weld on the torque arm stay mount on the swingarm. Will need to fabricate a bracket to attach the master cylinder/ pivot arm but have it mocked up and so far I am pleased with how it is turning out. I tried to keep this conversion 100% British parts but the stock rear master cylinder is just too large to fit behind the side panels so had to use once from a dirt bike.

I also tried searching the Web to see if anyone else has done a rear disc swap on an A65 with a stock frame and only came up with one result and it was never finished so this may be a 1 of 1???

LSR6.jpg LSR7.jpg LSR8.jpg LSR9.jpg

1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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Nice Chris, Is this so you can change the sprockets?

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Originally Posted by pushrod tom
Nice Chris, Is this so you can change the sprockets?
Tom, Yes on the sprocket changeability. I was thinking of going down to a 45t from the stock 47t. The motor should have plenty enough power to pull it.

Last edited by Blown Income; 01/10/22 2:06 pm.

1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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Nice set up on the brake. See you use Sun rims also, really like them on my BSA.


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There was an OIF A65 that kept appearing on ebay in the UK with disc front and rear, they had kept the left side operating brake lever too and welded an arm at the back of it. I liked the idea and have the parts to the the conversion myself... Though I would use a different method of actuating the master cylinder. I think with the welded on arm it is likely to bend the pushrod going into the master cylinder, something with a linkage would look neater and perform better, something similar to what your doing there but with the master cylinder closer to the brake lever (though this would be with standard food controls).

Did the sprocket only need shimming outwards to gain alignment?


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Originally Posted by Allan G
There was an OIF A65 that kept appearing on ebay in the UK with disc front and rear, they had kept the left side operating brake lever too and welded an arm at the back of it. I liked the idea and have the parts to the the conversion myself... Though I would use a different method of actuating the master cylinder. I think with the welded on arm it is likely to bend the pushrod going into the master cylinder, something with a linkage would look neater and perform better, something similar to what your doing there but with the master cylinder closer to the brake lever (though this would be with standard food controls).

Did the sprocket only need shimming outwards to gain alignment?
Allan, I tried to get the master cylinder close to the lever but this would have made the master cylinder exposed and both the resevoir hose and brake line were in close proximity to the chain which I wasnt fond of so came up with this location.

For the sprocket alignment, I had to shim the entire wheel over to the timing side of the bike roughly 3/8". I guess the BSA A65 sprocket is in a different plane than the T140's. Luckily there was enough room on the disc side to allow for this. Not sure if the T140 swingarm is different than the OIF A65 version (other than brake stay mounts) but glad it worked out, at least so far.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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This is such a bodge on mine but you could make something similar and try putting it at the lever, mount it to the peg bracket and peg bolt on a thin plate maybe and move the pivot on the lever. I think you could make something pretty neat compared to my sad effort. Though it works perfectly.

[Linked Image from i.postimg.cc]

This was a bit neater till I high sided it and broke it off and re-welded and bolted bits frown

Last edited by Mark Parker; 01/10/22 9:59 pm.

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Mark,

I definitely looked into making some sort of bracket/ plate setup to mount the master cylinder direct to the lever but routing of the brake line and reservoir line got really close to the chain and didn't want to have any issues with a Tech Inspector during pre-race inspection so I figured this was the "safest" route. If I were to build an OIF for the street with disc brakes front and rear, I would try to make the rear cylinder work in another location trying to utilize the Triumph master cylinder (maybe an upcoming build??).


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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Not a BSA, but the home made rear caliper and 19 inch Trident wheel on my hunk of junk...I bet money the Triumph has the worst combustion chamber.This Triumph ran 133 mph at Loring with 4.28 overall gearing.
Chris, nice bike, and I sincerly hope you bring home the gold...

206E6A47-5A85-409C-9068-39C6C596BEA9.jpeg

61 hot rod A10, 89 Honda 650NT .On a bike you can out run the demons
"I don't know what the world may need
But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"
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HB, That bike was fast straight off the trailer! With the rear drum setup with a 47t sprocket and a gearbox that wouldnt hold 3rd gear under power with the crazy winds we used to get at Ohio, I managed 134mph. Never got to test the bike before the track closed with the undercut GB gears so hoping for the best this go around at Loring. Current records in the MPS/PG-750/4 class is 100.697mph in the mile and 104.975mph in the mile and a half. I have rear sprockets in 47t, 45t and 43t so I hope I have enough adjustability for track conditions and putting the power to the ground. Would be great to add 40+mph to the existing record!


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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I think your bike can run 140 easily......if the wind is not a factor..The wind at Maine is worse than Ohio I believe..
The bike was fast off the trailer because I am not a great pits tuner...So I treated it like a sore dick.....don't screw with it


61 hot rod A10, 89 Honda 650NT .On a bike you can out run the demons
"I don't know what the world may need
But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"
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Tony, How did you fit up the rear master cylinder on your? Do you have a photo from that side?? I think youre right, 140mph should be achievable. I have a goal (which may be outta reach but you never know until you really try) of 150mph in the mile and a half without any power adders. Maybe I will get lucky and have a great tailwind. Plan is to be ready by end of May for the July event.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
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the thing about wind is that it can blow both ways. the week i threw a rod in mkne, there was a steady 12 mph tailwind for two days. i was crying.

the kids destroyed the OHC 250 records, bumping from 107 to 109. its always the exceptional runs that makes a record thst lasts. but you have to be there to get them


i'm old enough to remember when patriotism meant not trying to overthrow the government.
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