Working with a BSA marked primary chain. 69 links, but when I measure the pitch and the width, the dimensions are not according to the Book of Standards, but are wider (.410 instead of .305) and the length that should be 34" is closer to 34 1/2" although no stretching is evident. Am I adding a link to the measurement? Or is this chain meant for another model

email (option): unpob@yahoo.com

That's a cool chain. Don't you need half a link for the primary chain? or was it the rear chain that needed that.

Henk

email (option): ahum@quicknet.nl

Hi Henri..Are you measuring chain width between the inner plates? (ie the width of the rollers)...Ian

Oops! .310 there Ian...S/B .305 it has the correct number of links 69, will go and measure the sproket...Henk, is this what you were looking for

email (option): unpob@yahoo.com

My mistake, comes out to .305. As spec.,

email (option): unpob@yahoo.com

Hi Henri..I'd be interested to know what rules govern sprocket dimensions..something I have never gone into...It would seem more logical to have made them .312"(5/16") not a 'bastard' size (.305")...Ian

Scratching my head on that one, not sure how to make sense of the figures given for the engine sproket.

19 teeth
OD of teeth would not be it,
Root dia is not it either

Not available it seems. But makes sense on your observation.

email (option): unpob@yahoo.com

hi henri,if you google ''diametrial pich'' then google sprockets, all will be revealed,if you can get your head round the first equasion,gear cutting is an absolute science,wonderful if you know someone who knows the science,dont get in too deep,cheers rick

email (option): richardholt@rocketmail.com

shouldnt the primary chain be continueus because of the speed of revolutions

Roger, have seen them both ways. Don't know which is correct.

email (option): unpob@yahoo.com