Hi there I have got a B33 motor. Here in the uk they are hard to come by. I have been trawling the forums for advice regarding the head being welded. This has been done. Here are pictures of what I found when the engine was dismantled to examine/repair (it's been in a yard for years). It's a lightned crank with a polished conrod (excuse the watermark)
And work done on the rockers
Also has posh valves
As well as these there was a high compression piston and nice cams. Here's a list Cams 65-1891 65-2442 piston 65-1267 1/2mm os inlet valve 65-1632 (g2 on it) exhaust vave is hard to make out, I can just see bsa & g2.
I have a couple of Q's Does anybody recognise the cam partnumbers? I have seen 1 of them on pearsons site. Are these touring? or what? any advice from others in this field would be apreciated cheers
The dynamic compression ratio determines what octane fuel you need. You would need to measure the static compression ratio and then figure out the profile of the cams which you could do with a degree wheel and a dial gauge.
According to Bacon's Singles Resto book the 65-1891 was used around 1954/555 for exhaust on some 350 and 500 Clubman, some 350 Tourers, at least one 350 scrambler and some 54/55 Race machines. The timing is 60 85 85 60. These are all CB or DB engines.
Without frequent roadside repairs there is no fun in riding!
The 65-1891 exhaust cam is listed for the 350 Clubman. It is designed to be fitted with the 10 degree advance pinion. It has a longer duration than the more typical 65-2446 cam many of us use in both race and road GSs.
That all being said, I've tried using the 1891 a couple of times over the years with poor results in my 500 DBDs. However the 350 GSrs really like them. hmmm
For sale: 65-1891 cam and a 10 degree advance pinion
Thank You. My conrod has 66-483 on it. I cannot find any numbers on the crank. but I have noticed a slight difference in the lenght of the drive side shaft compared to b31. making it difficult to fit the cush drive
Drive shafts for alloy chaincases were just a smiggen longer than drives for tin chaincases but they are same at the other end so it is easy to get them mixed up. Drives for stationary engines or for non motorcycle applications were also longer. BSA made engines for all sorts of things other than motorcycles. They made them on the same lines with the same tooling so they will look like they fit till you try and line things up when suddenly the primary is 1/2" too far out or so close that the clutch can not line up. We buy stuff for swaps or on evil bay from traders who have either no idea or just a rough working knowledge then wonder why they don't actually fit. DID you measure it from end to end first ?
I have to take some measurements, but this thing must have come from a running bike before. It was more likely to have been some sort of goldie replica, as there were the metal wound oil lines hanging off it
I have a spare b31 motor that i had to nick the cases off for this one. The con rod in that has the same part no also. b31 flywheel has part number on the counterweight section. that part of the light crank has no number. I can't find a number on this crank which makes me wonder if somebody turned all that metal off to replicate the posh crank
It's a mysterious motor. looks like somebody got a bunch of zb bits put in an iron motor. and used a bizzare cam combo.
Looks interesting tho'! :-) The iron motor can be made to go pretty quick. Maybe with slightly softer cams than these? They also run very hot (on petrol) when highly tuned. Oh yes, they go BANG as well! The long rods aren't safe much over 6000rpm (they are all 50-65 years old now) Seems to have built to something like B34 competition spec. But the crank is not B33. It looks very much like ZB32GS - if not genuine it would be fairly straighforward to convert B31 flywheels to that spec. All the B33/34 cranks were the heavier castings (very similar to M20 wheels). I always assumed this to be due to it being easier to balance the assy. with heavier 500 piston & workload. There is another recent & useful thread on early / ZB crank ID. Goldie long rods are 66-1321 not the 66-483 B31/3 but I suspect they were the same rod but polished!? (Never seen a numbered ZB GS rod). No GS cranks I've seen have had numbers stamped. Early cases are all the same timing side. ZB34 drive side cases I have are heavier with more strengthening webs than ZB31/2/33 which are the same number as B32GS up to 1951 - GS then got a stronger drive side. You must check that valve springs dont get coil bound at full lift. They will with these cams! The very high lift 1891 & + 10 deg. pinion is the best racing exh. cam for CB-DB350's. Without the pinion you can't adjust the valve timing any less than +/- 20deg.
Last edited by flowboy; 02/26/152:33 pm. Reason: detail
Joined: Feb 2011 Posts: 3,352Boomer
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I knew an old boy that raced for BSA at Daytona starting in '48. His first ride was on a YB34, iron engine 500cc. He thought the YB34 had more power and ran better than the later ZB34 alloy engines. His YB34 was a rigid frame and was much preferred over the plunger frame model.