Scooterotica

I have exactly the same problem as you and thanks to the foto I think it must be the crownwheel. I have the same crownwheel (I think ) which is a MBD and the only solution that I can think of is to drop the front sprocket 1 tooth.

cheers

Steve

Think I read that 15 tooth front sprocket is advised as the lowest as the chain doesnt fit properly,even tho they are made smaller.Annoyingly the 81 pitch chain is recommended for a 15/48 setup,both in stickys manual and on the shop website I got it from.Half links are available,so could look into that.Would like to hear opinions on a smaller font sprocket tho.

A smaller front sprocket will alter the gear ratio. Something you are already doing with the 15/48. (Or would be if the chain fitted) I saw where you obtained the crown wheel, but I still think it's the problem. Did you buy it with a view to changing the ratios or just because you want a 6-plate clutch?
It is posible to fit a half-link, I've done it. But you have to be confident in your own ability to rejoin the chain.

I realise its more expense but if you want to use these sprockets why not use the 82 and a pull down tensioner.

Ive ordered that type of tensioner but theres a lot of slack to take up with an 82 link chain.I dont suppose it matters.The chain drops down just pass the top stud for the chain guides.

Daggs where did you get the half link from , I cant seem to find them anywhere.

Here.
http://www.scooterrestorations.com/lamb ... etta-x-30/

Put push down tensioner in place,worried by the angle between sprocket and the tensioner,is it too much,also is it normal to have to undo the nylon block to get to the top fixing bolt? Also bit concerned about having to remove the bottom chain guide to get the tensioner to fit.

This weekend I had exactly the same prob on an engine I rebuilt for a mate.

I had a new 81 link chain and no way in hell would it fit.

Luckely for me he already had a 82 and pulldown tensioner. I didnt have to remove the plastic block and could just about get a hex key between the chain and block.

The chain is not supertight and he has ran it like this for 2 years without an issue so i`m not too worried.

The angle of the chain at the end of the tensioner is no worse than round the front sprocket so I wouldn't worry about that too much.