Breathing New Life Into a BSA Bantam (Part II)

Click here to see part 1

Last month I described my efforts in resurrecting the chassis of my little D7 Bantam. This month as Paul Harvey would say: "here is the rest of the story". In the pile of parts were 5 or 6 crankcases plus many boxes of engine parts. There was one box of heads and another of crankshafts. There were coffee cans full of motor giblets and of course there were several boxes of NOS parts still in their wrappers. When we bought all of this we had ideas of building 3 bikes but as we sorted things out we could see that we were going to be hard-pressed to get two runners. We had only 3 cylinders, one of which was cracked, one complete carburetor, one complete NOS electrical stator, and two flywheels. Examination of the crankshafts revealed lots of rust. Only one of the cranks might have been serviceable but the rod bearing was awfully loose. The rest were shot.

Dink at D&D told us that George Nance (george.nance@worldnet.att.net) in Long Beach Mississippi had a lot of Bantam NOS parts and that we should contact him. Sure enough George had rod kits, Wipack electrical stators and cables all for 50 cents on the dollar (based on some BSA price list of unknown origin but nevertheless reasonable). We left Long Beach with the parts we needed (including a new fuel cap with a built-in measuring cup for the oil and mixing instruction stamped on top) all for about $100. By the way George has a garage full of classics including a Vincent, a BSA Gold Star and an interesting Triton.

Back to the pile. We fished out two good looking cases and stripped and cleaned them. I took the bearings and seals to Motion Industries here in Mobile and they were able to cross reference and supply all but one transmission bearing which we were able to obtain from Baxter Cycle . We had two new pistons which would fit the good cylinders. Jim used a standard cylinder and piston while I would have to bore mine to fit a new .020" over piston that was in the NOS pile. We took 4 175cc crankshafts, the rod kits and the cylinders to Steve McClintock’s machine shop in Grand Bay, Alabama. Steve bored the cylinders (no problem) and built up two crankshafts with the rod kits (big problem). After much trial and error he was able to make two straight crankshafts which he fitted to the two cases. The first time the cases were assembled the shaft wobbled by about .040 inch. He literally went through all four shafts before he found combinations that would press together and run true. The charge was reasonable, however, and we were ready to finish assembly.

Scouring the boxes of parts we found two critical items missing. One was a points cam (something that could be made if all else failed) and the other was the flywheel nut (a typical weird British thread). Wonder of wonders Baxter had both items. After some fiddling we had the top ends built. On the first assembly the new wrist pin was too tight in the rod’s needle bearings which caused the piston to bind in the cylinder. I found a used pin that had a thou or two worn off of it and, on reassembly, it fit fine.

My flat-topped piston was the genuine BSA item while Jim’s piston was some sort of after-market variety with a domed top and used only 2 rings as opposed to the normal 3. It was also missing the locating pins for the rings which Steve McClintok fabricated for us. We fitted a set of BSA rings to the after-market piston which seemed to fit fine. After final assembly we installed Jim’s motor in his chassis. We timed it, put the one complete carburetor on it, and it started right up. It sounded pretty good. The next day, however, Jim called and said that it wouldn’t start. I went over to give him a hand. Everything seemed pretty good except that it wasn’t drawing much air through the carb. We first thought about a possible air leak at the cylinder base gasket so we took off the cylinder. To our surprise we found that the rings were frozen on the piston. Jim thought that maybe he hadn’t cleaned all of the honing grit out of the cylinder. He washed everything with soap and water, freed up the rings and we put it back together, It stated fine - once. The rings froze again. Disassembly revealed two things. The domed head that matched the piston exposed several mm of the composite head gasket that was noticeably charred. Secondly, the rings fit with almost zero clearance in the ring groves of the piston. The rings were hand lapped on a flat stone to make them .002 thinner. The head gasket was thrown away and the head was lapped true on the stone and was fitted directly to the cylinder with a little aluminum spray paint for a sealer. That solved the problem as it now starts with just one or two kicks.

Back to my motor. I decided to leave the head gasket be and installed the motor in my newly painted chassis. The bike uses a 22 mm Amal monobloc carb #375. We had a #375 body and slide but no top or ring for it. Jim has a box of Amal carb parts and I found enough parts to build a 26 mm monobloc. I used a 150 main jet which I eventually replaced with a 140. As you could see in the before pictures last month the exhaust system was grim. Just to get it started I brazed patches over the bigger holes and bolted it up to see if it would run. It started right up and, after a little fiddling with the needle in the carb, ran pretty good except for the exhaust leaks that were spitting exhaust oil on the front fender. A call to Domi Racer revealed that they had both an exhaust pipe and an after-market muffler (about $160 for the two) which I promptly bought. They looked beautiful and fit perfectly.

I found two problems with the motor. First, the kick starter spring was not wound tight enough. As a result the starter peddle did not always come all the way back up on its own. That is pretty easy to fix as the spring is just under the right side cover. The second problem is that it momentarily jumps out of second gear if you really get on it. I thought that I had chosen good gears for the transmission but I guess not. To fix that problem means splitting the cases so I think I will live with that for a while. I was unable to find the original funky air cleaner with the German-style rotating choke so I fit a round Amal cleaner which to its credit does have an efficient dry element. It does not look bad and fits in the frame well. If anyone out there has a correct air filter that they would part with please drop me a line.

Click here to view the final result.

My D7 was fitted with a battery which really does nothing but run the parking light. The spark is magneto and the lights are direct from the stator. A second stator charges the battery. I omitted the battery and used the second stator to light the stop light and supply the horn. American law does not require a parking light. Jim’s D7 was a slightly cheaper model which only had direct lighting. For a horn a squeeze bulb horn is fitted inside the steering head pivot. A brake light was considered a luxury and not even fitted by BSA. To get around the parking light law they installed a flashlight battery holder inside the headlight shell. Somewhere along the line the battery was left in place way beyond its useful life. It corroded and rusted out the holder in Jim's Bantam such that little remains of it today. By the way, if you want to see Jim's Bantam click on Pensacola Show . There is also a beautiful D1 Bantam featured there. Finally, you should check out Chuck Browning's D1 BSA which he says stands for Baddest Scooter Alive .

How does it run? Well lets just say that it is not a crotch rocket. It is under-powered and under-geared all the way. Several years ago I restored a 125 Harley Hummer. The performance of the Bantam is very similar. First gear is too low second gear is promising and third is a let-down. Once under way, however, it does hum down the road at a comfortable cruise. I sold the Bantam to Nigel Smith in 2006 to make room for my newer restorations in my cramped workshop. The good news is that it went to a good home and will continue to be appreciated to interesting piece of history that it represents.

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