BSA B50 Flat track & Ice racing.

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send me your photo and I publish it here.
B50 homepage

Some new photos from Stan.

BSA B50 Flattracker

Getting ready for a racer bike show in Milwaukee, Wi. ...Stan

BSA B50 Flattracker

Left side of one of the most sucessful BSA race bikes in history, even if "race",
in this case, doesn't mean parading around on pavement.

BSA B50 Flattracker

Check out the licence plate on the hauler / van

BSA B50 Flattracker

Stan & Mike Gilkey ( Driver ) won the AHRMA 70's singles season championship 1999.

BSA B50 Flattracker

See photo from Mike Gilkey winning AHRMA "TT" National at Peoria, 1999 68 kb

See More of engine 35 kb

In the Peoria "TT" ( 1st place) , we ran a modified stock ( above ) frame instead of my custom flattrack frame because the flattrack frame doesn't have as much wheel travel or ground clearance as the modified frame. If you look @ the street bike frame of mine, you will see exactly what frame we were using. The engine is dropped 1" and the shock "eyes" are equal distant from the swingarm pivot. The swingarm is modified some to line up the wheels so it will turn left better. (all unit singles have the rear wheel offset to the left of the front wheel to balance the engines offset weight) If you line up the wheels on a street bike, the thing will want to fall to the left . Also I used the complete front end off a '86 KLR600 Kawasaki with some home made "Triple Clamps" to adapt them to the BSA frame and to get more wheel clearance for the wide 19" rim I laced up. I welded a little triangle into the timing side cover to mount a higher foot peg "ala" CCM. The kickstart lever is from an old Suzuki RM 125 welded onto a BSA bottom. The carb is a little 38 mm Mikuni round slide. I made a really tucked in high exhaust pipe and got the whole mess finished up @2:30 AM the morning we were leaving for the Friday Night 1/4 mile track. The first time we heard it run was in the pits of the Short track so I'm glad everything went together well. I finished up making the number plates and bled the brakes @ the track and everything else worked,,,,,,,,
COOL !!!


The 1999 season ended with 6 wins, 2 at 3rd, 1 at 4th and 1 at 9th place.
Total points 163. Closest competitor had 138 Points.
Look at Stan´s street bike.

BSA B50 Flattrackerlogo Stanley Millard´s BSA B50 Flattracker
Stanley Millard´s BSA B50 Flattracker
with driver Brian Kromroy (Wisconsin,USA)

Stanley built the frame in 1979 from 1018 mild steel tube and updated the swingarm in 1985 to a Kawasaki GPz 750 unit. The bike is the last BSA to earn it's rider AMA class advancement points.

Jimmy Sumner winning at Elkhorn in 1990.

The bike is 510.7cc. It has a lightened crankshaft with a 1/2" longer Carrillo connecting rod. + .040" Arias Porsche 911 piston, titanium intake valve from a Buick V6 and a titanium exhaust valve from a 350 Chevrolet. The cam is a Megacycle 541X4, the carb is a 41mm Mikuni flat slide and he has a reed valve in the crancase breather.

Damon´s Flattracker
Damon Lengle´s BSA B50
Georgia USA
I built this B50 4yrs. ago to race AHRMA Flattrack here in the states. Won the Southeast Sportsman 600 class with it.

I got the motor with the B50 bike that I had for vintage MX.(that bike won its class for the season also but not ridden by me ) It was just sitting around so I decided to make a Flattracker with it. The engine was completely gone thru. I made it a completely caged ball bearing bottom end in the crankcases. Lightened the crank by machining it off the inside. The crankcases basicly went together like a 2 stroke but it did not need to be pulled together with a puller tool. The rod was to be a aluminum rod out of a Jawa speedway engine but I was pressed for time and ended up using a Carrillo rod. The cam was a old BSA racing cam dont know the specs on it. The piston was a 12 to 1 comp. Gold Star piston from MIC. Head was ported by me, with oversize SS valves. The rocker box had lightened and polished rockers. I used countersunk SS bolts instead of the standard studs. This was unique to this bike as they are not caphead (allen) bolts but truely countersink type bolt heads. This makes it possible to remove the rocker box in the tightest of frames (ie the Champion racing frame). Inner clutch hub was disasembled and Lightened then new rubbers replaced and welded together. Outer clutch (chain wheel in BSA lingo) was a NEB aluminum piece. Same for the pressure plate. Alternator rotor and stator completely eliminated and a spacer (Aluminum) was put in its place. Used a JWIS primary chain which allowed me not to use the chaintensioner. The kicker mechanisism was completely eliminated. outer cover plugged and welded. Inner cover had a aluminum plug made and bored to accept the needle bearing. The clutch plates were Barnett with aluminum plates driven and driving. Ignition was electronic Interspan with dual lead to the dual spark plug head. The frame is a Champion Racing frame for Flattrack racing that was originally built for 72~75 Yamaha 250 2 stroke engines (DTs &early YZ). The frame needed to be modified to accept the B50 engine. First the leftside frame rail had to be lowered to clear the primary side cover. A frame rail that runs under the top rail to brace the frame had to be cut and turned up to clear the top of the engine, I also used a later style Champion frames Swing arm because it uses the sliding style chain adjusters instead of the old style snail plate type.Wheels are standard issue for Flattrack type from Kennedy/Barnes. Front forks are Cerriani with aluminum clamps made for racing. Exhaust was built by me with a aluminum Supertrapp. Carb. is a 38 mikuni spigot type mounted to the intake spigot I welded into the head. Used late model Yamaha YZ 125/250 throttle and cable. (the best throttle to use period). Are you ready to build one now after all that? Just kidding, it was really fun to do being there is not another like it.

Damon Lengle

BSA B50 Flattracker
Scootin-Newton´s BSA B50 Iceracer.
It have a MX cam and a 34 mikuni
Look at Scootin-Newton´s web pageNew url

BSA B50 Flattracker
See More 28 kb
This is the same bike as above!! But in summer style.

This winter i put it in a Cro/Moly dirt track frame, With a Ceriani fork, Champion Gas tank, spun aluminum oil tank, Spool front wheel, and got the disc brake working. The only thing missing is a Champion fender and seat.

BSA B50 Dirttracker
BSA B50 dirttracker owned by Norm Lehfelt.
This one is in a BOSS frame.
Photo from Scootin-Newton.


Updated 14:22 2005-04-05
© Rickard Nebrér