b40 primary chain question

[chaz]

the B40 primary chain was loose and would not tighten up with the tensioner at max.
I bought a new Regina chain, same ammount of links and looks ok until I fitted it. there is no play on top or bottom run. when I try to turn over on the kick start its very tight and only just turns the crank , too much force could do damage. Ive pulled apart twice, and even tried the old chain same results, old chain too slack, new chain too tight.

any one had similar experiences.
BTW, Ive checked both basket and engine sprocket run and both within 0.010" of each other..

[AdrianS]

Are you sure the new chain is the correct one? The pitch could be very slightly different. I know there are metric chains and imperial chains and there is a difference.

[chaz]

just had it all apart again, still tight.
Ive re checked the part number and a couple of sites and its the right chain, Drags are out of the two they list, Wassells supply the trade and a few suppliers I use show the same number as on my box. I dont want to put the old one back in as its run out of adjustment and if snaps   will cause more problems, likewise if its too tight same outcome...

[Beesy]

Only other thing I could think of is that either the drive sprocket or clutch basket may have been changed to a bigger one making a standard chain too short.

The engine drive shaft and the clutch shaft run on fixed centres don't they? So it has to be either new chain is duff and too short or the sprockets changed for bigger ones therefore requiring a long chain.

What is length  of old chain compared to new and how many teeth on drive sprocket/clutch basket?

[chaz]

23t crank sprocket is as per RR's book so standard, clutch is 4 friction/5 steel so think standard, same number of links on both chains, both use 1/4" rollers and same width and lengths of links but you can see the old one has stretched when side by side.
Im tempted to ask if anyone has a useable  used chain I can try. yes, being unit the centres are fixed  and as mentioned previously the old chain is out of limits, the tensioner pushed up is still letting the chain flap too loose.

[Beesy]

I think it has to be the chain then. If everything is standard.

Ask the vendor to measure another one and compare it to you new one.

I was just wondering on the length difference between your new and old ones to see if it seems plausible that the difference is all down to wear.

[AdrianS]

I think it is the chain also.

As said previously, some sellers sell metric equivalents which may be close in size but not exactly the same. Had a lot of problems with a Bantam rear chain replacement which was close, but not the same as the original. Vendor swore blind it was a genuine chain!

[chaz]

thanks , will ask.
as they supply trade I suspect many more wrong so will see if they have had messages.