Tappet specifications

Posted by colin_sharpe at February 16. 2012

I need the dimensions for the outside diameters of tappets and inside diameters of tappet guides for lightweight twins. I have a "Maintenance manual" for the Electra, and the more general "Twins Rebuild Manual", but neither of these give the dimensions/tolerances I need.

Just out of interest, who has the drawings and factory records from Norton? These would be a real asset to rebuilders of obsolete and somewhat unfashionable motor bikes.

Re: Tappet specifications

Posted by peter_holland at February 20. 2012

Colin,

I am looking at the 'Twin Cylinder Manual', published by Norton, and with data for Lightweight Twins and Heavyweight Twins. Is this what you call the 'Twins Rebuild Manual'?

Page 80 has half the information you need. An educated guess will get the other half.

Is there a reason you choose to post and take random replies from the internet rather than going to the NOC Lightweight Specialist? I'm sure he could answer your questions.

Re: Tappet specifications

Posted by lionel_yexley at February 21. 2012

Hi Colin

The data Peter mentions, just in case you haven't got that Twin Cylinder Manual, is as follows: -

Tappet bore size....7505" / .7495"; Tappet guide bore....439" / .438"

Cheers, Lionel

Re: Tappet specifications

Posted by colin_sharpe at February 23. 2012

Thanks Lionel. I did finally find the sizes in the book, but I still don't know what size the tappet stem should be/what clearance there should be between tappet and guide. Ian at spares told me they have plenty of tappets in stock, but at 30 quid a time I don't want to buy new ones if I don't have to. Maybe I should just take Peter's advice and ask Andy?