From the top. The B series fly wheels will be too light for any 500 cc sloper.
At best the primary side engine shaft from a B series probably could be used in the sloper as there only seems to be 2 different diameters used on the engine shafts on singles. A thin one for the light weights and a thicker one for the rest. The lengths do vary a bit but the splines are the same.
So at the worst you would have to get the flywheels made and use engine shafts off latter models. Cornucopia in Germany keep a very large range of rods for pre WWII bikes.
However as Pachy had already stated we really need to know the engine number. BSA used a letter code pre WWII which is the bore & stroke for the engine regardless of the layout so an "S" engine will be 80 x 98 regardless of if it was vertical, sloped, SV, OHV, single or twin ported. Thus any "S" series crank could be made to fit as the only difference will be the amount of counter weight & where it is positioned but the parts book lists several different fly wheels
30's projects can be surprisingly expensive too, particularly De Luxe models,. A tank top instrument panel for a 35 sloper (& other models), with the gauges & switch, sold on eBay last month for nearly $1000.00 but I have seen a few sloper bottom ends turn up on eBay.
S32-8 was listed as a 4.93 OHV De Luxe Bore 80mm Stroke 98mm Capacity 493cc (As apposed to the 499 capacity motors, which were "upright" engined bikes like the "W" range)
Standard crank & rod for that bike is listed in original BSA parts catalogue as:
Rod = 24-273 Drive side flywheel = 24-1283 Gear side flywheel = 24-1257 (That assembly is shared with the model H32-9 557cc SV)
Also listed for S32-8 is the "Red Star" Sports Special version crankshaft, used with uprated valve springs, special cams, high comp piston & racing magneto ETC These were bench tested & certified to give 25HP, a red star was then stenciled onto the timing case. The red star crank & rod for S32-8 is: Rod = 24-275 Drive side flywheel 24-1263 Gear side flywheel 24-1265
What Patchy may not be aware of is there is a mistake in the BSAOC UK's engine & frame number listing on the web. He is correct, with a Z8 engine number your bike will be the last year of the 4.93 Hp motor. You will find this site most help full Leons 1930's BSA Email Leon, he is a nice bloke and very handy for sniffing out odd parts
Yes I'm not aware of BSAOC info & don't use their site. My info is from Original BSA parts books & specs.
Leon's site is extremely useful & it helped me alot during a resto I was doing about 8yrs ago. I see on Leon's 1932 catalogue scan the red star version of S8 isn't mentioned, although it is listed in the BSA parts catalogue as an option for that year.
RE Capacity, it's easily cross referenced by the equation...
Bore 8cm ÷ 2 = 4cm x stroke 9.8cm = 39.2 x Pi 3.142 = 123.1664 x half the bore 4 = 492.66cc
There obviously were different versions. None of what I have here is exactly the same as any of his. I used to think these inconsistancies were just sloppy research but over the years I have come to believe that BSA did put out different versions of catalogues for different regions from the very start so the "Americianized " model changes were not just a Post WWII idea.
I have a red star Sloper 1931. The star is under the magneto on the crankcase by the way.. not on the timing chest as myth says. (Which make sense.. the engines were probably lined up on a shelf with the rear of the engine facing the storeman). The crankshaft from the red star engine is lighter than standard. I chose to fit the heavier crank with the higher compression piston. My heavier crank came out of a standard engine 'polished' with a stain on one side (from sitting in the oil which had thickened like grease after 50 years). BSA did a lot of selection for best fit and this was probably normal manufacturing tolerance so check and correct for end float. My standard crankshaft was a little wider by about 0.6mm, so would have stressed the bearings when tightening up the crankcase, so When Alpha fitted a new big end for me, i had them turn a lttle of the end face, choosing the timing side. When running in, i struggled to adjust the oil flow low enough to avoid it comng out every orifice including the top of the push rod tubes (shouldn't reach that high!). I put this down to blow by on the new rings as the engines have no breather. A breather would help a tuned engine with the adjuster set for higher oil circulation and could be fitted discretely in place of the primary chain oiler or I have seen fitted to the oil filling spout. With the engine tending to seize on long inclines at 60mph, its 'comfortable' speed, I settled to revert to standard compression and standard Engine sprocket with half turn open oil control as the red star gearing needs you to slip an awful lot in first to pull away. It now has a comfortable riding speed of 45-50, which suits me, is oil tight and does not seize. Compression is excellent on its two rings but if you are going to tune, try to find a later high comp piston with an oil control ring.. Heplex made these I think. This will help you turn up the oil flow. I fitted longer blue star valve springs which have lower rates but compress more to give the same force when closed. I did this to ease the forces on the rocker box when the valves were open. I.e, a standard sloper valve spring is actually pretty strong and suited to a tuned engine. The rocker box is prone to crack. In the end I made a new rocker box of brazed steel plates and blocks and painted it silver. No one ever notices, it looks identical.. but i trust it. Someone in east EU is re-casting rocker boxes but I checked his alloy and it is 'half tensile strength' of the original. BSA cast with copper rich Dural - from finding copper streaks in my gear box casting after shot blasting.. which would be why the castings corrode so much. BSA would have been party to the Dural recipe after it was recovered from Zeppelin at the end of WW1..
oh.. by the way, BSA knew of that tendency to seize on long-labouring inclines or with sidecars... They supplied an auxillary oil tank option which fitted under the seat, connected to a pump operated by a lever at the heel of your left foot. I had one of these tanks but no pump or foot lever, picked up on eBay but I never fitted it. My sloper, being '31, has a battery in the place where the tank fitted. Also, I found the tank fitted the Slopers with tubular top frames more easily as the seat stem is longer, but I have the drop-forged top frame. The oil was delivered by the pump in to the screw-plugged hole which can be found under the inlet port, at at the base of the rear of the cylinder.
Someone in east EU is re-casting rocker boxes but I checked his alloy and it is 'half tensile strength' of the original. BSA cast with copper rich Dural - from finding copper streaks in my gear box casting after shot blasting.. which would be why the castings corrode so much. BSA would have been party to the Dural recipe after it was recovered from Zeppelin at the end of WW1..
I woud not have thought that BSA used Dural for the castings as it is a bitch to gravity sand cast and the couple of covers I have here look like they were sand castings but as I no longer have access to the chem lab or metallography gear I can not confirm this one way or the other. The other problem is that in the 30's it was an "exotic" and thus too expensive alloy to use on a motorcycle In either case the Cu is totally dissolved into the Al and can not come out of the metal under any circumstances. Straight Al-Cu alloys do corrode badly because the Cu content prevents the alloy building up a strong coherent oxide layer. Latter additions of Mn cured this problem to a large degree and the final versions usually had both Mn & Mg added to make it a quaternary alloy. If any one can come up with an economical way of removing Cu from Al please contact me as I could turn us both into millionaires in no time flat as high Cu has to be diluted out of casting alloys with pure Al which knock the profits for a six. So any red staining in your box would be either from a lubricant , sealant or a dezincified brass bushing. Of these the latter is the most probable as early gear oils ( till the wide adoption of brass syncro cones ) contained a lot of sulphur which is why BSA specified engine oil to be used in their gearboxes.
Well... there's the challenge eh.. Maybe someone out there can find out if it is Dural?. I too am away now from making the equipment that would tell us.
But would I be surprised, well no. I can weld but Aluminium is tricky at the best of times, So when I took my sloper rocker box to a coded welder from the aircraft industry, he admittedly struggled to know what was going on. Consider also that BSA sometimes applied, (quote from 1931 sales brochure for the S31-10) "...and special matt finish to the crankcase and gearbox" ... So it all points to something special going on with those castings eh!
I think, with our 90 years of knowledge since, we perhaps might not see how advanced BSA were with Materials technology in the MID 20's. The Steel Crank shaft, And forged steel top frame, even the hardened alloy wheel nuts (Ever tried filing one!). I suggest what we have lost, 90 years on, is a perspective from within that Era...
I wonder how advanced the sloper was proving to be, as the designers worked through 1925 and what technical issues they had to overcome to put together something that was so very different to all that was around them. But BSA offered vast industrial resources back then, and I suggest they look to have made good use of the people/skills and resources to hand.
The Technology and the Production Engineering that "went in" was very leading stuff I suggest. Even the move to electric lights, drum brakes, new frame design, saddle tank etc had to win favour with a feckle and traditional market. An Engine so big it was tilted to shoe-horn in to the frame with an unprecedented choice of instrumentation in support.. and an unprecedented range of accessories to turn it in to a workhorse tailored for wherever it served within the colonies...
I'm impressed at how hard BSA worked to 'sell' the new technologies in their literature and how one-by-one they knocked down calls with 2-page spreads that we can only now guess at what prompted them... "the frame is over engined", "the main bearings will never survive", "the brakes are too small", "Electric lights are too complicated", "chrome is too showy"..
At my mere 50 years, and In trying to place myself within the era that has now sadly/probably left behind anyone buying one new from a showroom, I am not surpised that owners of these or the later model to which it was attributed, became known as Promenade Percy's.
I recall talking to a later Triumph Engineer Who recollected how they often looked to the BSA. e.g struggling to quieten their engine noises and how they studied BSA cams to reveal all they could.
Accepted, the mists of time might have me unduly passionate about a model I happen to own, but might those mists of time leave us a little blind as to how leading-edge BSA really were from the Mid 20's? Please excuse me for my beliefs, even if they are mere suspicions in truth. None-the-less ... for what I have seen and worked with, I tip my hat to the BSA design and production Engineering teams of the Mid 20's for setting the bar so high.