I just re tightened the primary chain on my 1965 A65 LR as per the manual, which states "1/8 in. of top to botom play" in the top section of chain, mid span. Now 1/8 in. play is darn near "tight" as well as I can figure. Is this right? or is there some secret meaning to this?. Ken
It is very close to tight...but I would modify the manual's directions to say "no less than 1/8" of play at any point in the primary drive's rotation". Rotate and check, rotate and check...do this at least four of five times. Runout in the crank sprocket and clutch basket as well as uneven wear in the chain can produce tight spots which you want to avoid.
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
Believe it or not, but the manufacturer of industrial chains and sprockets, Browning, described the identical process. For a few bucks you could buy an aftermarket chain tensioning measuring device, but I have found the freeplay, feel system to be adequate. The greater the center distance between sprockets the more free play. On the a65 you want it reasonably tight but not so tight that you put excessive load on the bearings which are further loaded when you accelerate. You will also wear out the chain prematurely if it is too tight and stretch it. If it is too loose you will know it when the rear wheel drives the engine..going down a hill with the throttle closed because now you have the tensioner on the driven side where it does not work so well.. I set mine where I can deflect the chain about 1/8 to 1/4 inch with modest force at the midpoint..whatever that is..... and it seems to work well.