Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board BSA B44 Cam Timing Marks

Hi folks. I’m reassembling a late-60s BSA Victor 441 motor. The manual says to align the timing marks on the oil pump gear and the cam gear. Simple enough. However, my cam gear has two timing marks. One is a line, and the other is an arrow. I’m inclined to line up the line mark, since it matches the mark on the oil gear. Any objections? Can you explain why there is an arrow mark on this cam? Thanks in advance!

Photo: https://www.dropbox.com/s/86z3zve35eyxcpg/BSA%20Cam%20Marks?dl=0

Experts may weigh in, but the Rupert Ratio book says in bold:
"If the V is present it must be used in preference to the dash"
So that's what I did.

Thank you very much! I can’t afford a Rupert Ratio 😭

Little over $40 with shipping????

BSA Unit Singles has downloadable workshop manuals. Easy enough to find what you’re looking for……print off and take to the shop.

I use Rupert’s more than any paper I’ve got but I use the parts manuals off of BSA Unit Singles more than anything.

Where on earth are you finding Rupert Ratio for $40? I have the BSA FSM, but it doesn’t even acknowledge the possibility of multiple timing marks.

Thank you!

Peter Quick ( BSA Unit Singles) has them too……a site sponsor and an all around nice guy.

Pretty much the same price.

https://www.bsaunitsingles.com/item.wws?cpubcode=BSA&sku=9781999823207

It'd be a good time to make a shopping list and let the book come along for the ride????

Does it say why the V is used in preference? it doesn't show as a "Must" on the image, just "V timing marks used in prefrence to other timing marks".. Just thinking that there must be a good reason why there are 2x timing marks and not just one?

Allan, Rupert's goes on to explain the issue.......in pretty good detail. Basically claiming that the "V" is the newer of the marks and should be used if present. States that the 'V"'s location can vary? Then gives you a way to check them. Very helpful.

I just checked my paper copy of the Workshop manual and my copy doesn't mention the "V" either. My guess is there's a Service Bulletin out there somewhere?

Just another reason to get a Rupert's.........worth every dime you pay for it.

Wheels can be moved easily from cam to cam over the years so I always check the timing before putting the timing inner cover on.

Thanks Gordon, my unit singles knowledge is very crude, I could build one up and get it running but the fine tuning and knowing what’s what is beyond me with them.

Looks like if you use the V mark then you’re retarding the cam (bringing the valve opening in later, by how many degrees would be 720 divided by the number of teeth. (720° being crankshaft degrees for 1 full rotation of the cam)

I'm going on memory here which can't be trusted but I think Ruperts mentions that the "V" can be off by a couple of teeth in either direction??? So if you change gears/cam you need to check.

Can't say I've ever run across that......at least so far.

Here is the explanation, from B25/50 Workshop manual 1971:

https://i.postimg.cc/8zXNv2Lp/IMG-20221126-003013a.jpg

My thought on the two marks is this: At some point in the development of the unit single (for whatever reason) they found that the original timing mark was not optimal. Rather than make a new gear with a new mark, they simply added a new mark (the "V") so that the gear could be used interchangeably with different models of the unit single. I have no idea whether this is correct, but it seems plausible. Industrial Engineers, back in the 50ties and 60ties were focused on simplicity in manufacturing and supply chains to improve efficiency and reduce cost. Changes to the supply chain or manufacturing process were minimized. This in part likely led to the demise of BSA. They were promoting bikes that were designed in the forties, and the Japanese embraced a wholly different philosophy and had newer designs and much improved motorcycles to offer.
Guys like me grew up in an age when long stroke pushrod engines were the norm, and we were comfortable working on them. I rarely work on today's engines and fortunately I don't have to very often. They really are better.

Mr Mike

The difference is a a few teeth, too much for a slight correction of an existing cam, there must have been a change in the cam at the same time as the new mark. Never looked into it but have swapped so many wheels over its just second nature to check the timing and ignore the marks.

I have never seen a valve timing chart or graph of the singles, but I also suspect that the addition of the second mark was in conjunction with a change in the cam profile. Probably a modest change of some sort. The timing mark change doesn't alter the relationship of opening and closing the valves relative to each other. it just changes the process relative to TDC. Are those marks on the 250's, 441's and 500's?
Mr Mike

From roughly 1965 onward, most unit singles used the same cam timing. B44GP's and B50MX's had their own different cam timing.