So, im pretty new to this and been messing with the timing for quite a bit now. I recently saw that im suppose to move the auto advance forward when I set the points to release the cigarette paper. Problem is, i dont know what the book means by setting the auto advance forward. Can anyone clarify? I have the distributor on the top, looks like a mushroom, not the side points...
I'm not familiar with the B-40 but generally the advance unit is set in position by removing the fixing bolt and add a washer under it to capture the advance unit in fully advanced position.If you are setting the timing with a degree wheel you can do some math and set the timing with the advance unit in its relaxed positionby subtracting the degree of advance and factoring in the speed of the advance unit ,probably half engine speed but again,I'm not familiar with this setup.
What it means is to rotate the points cam to the fully advanced position. On the side points you take out the points cam retaining bolt, rotate the cam fully then replace the bolt with a "special" washer that contacts the cam and prevents it springing back. The special washer is just a thick washer with an oversized hole in to so that slips over the protruberance of the drive shaft and sits on the cam itself then is clamped by the retaining bolt.
Joined: Sep 2002 Posts: 7,812Alex
BritBike Forum member
BritBike Forum member
Joined: Sep 2002
You need to rotate the points cam in the direction of engine rotation and hold it there while you check the points gap. I find it easier to connect a DVM across the points (between points wire and ground), set it on the audible continuity test setting and use that, rather than the cumbersome cigarette paper thing. You can also use a test light. The points should be just opening when the crankshaft is in the fully advanced position (piston 3/8" or 34 degrees btdc).
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Watch the BSA service sheet, it tells you to set the timing at the fully retarded position, once you have this position you turn the cam forwards to release the paper. Can't see this working well on your distibrutor which from you previous posts sounds well worn. My suggestion would be for you to get the later primary cover so you can strobe the timing and either get an unworn distributor or rebush your current one to stop the timing varying all the time (never done this but Rupert Ratio partially covers this).
Use the BSA service sheet method to get the bike to start and then strobe it to get the fully advanced timing correct.
As well as the new primary cover you will need to use a piston stop and a timing wheel to get the alternator rotor marked with the correct position to match the marks on the primary cover at the fully advanced point for the strobe to illuminate.
Once you have this done retiming will be easy and you can throw away the cigarette paper.