Set tap­pets on Brit twins

Most Bri­tish twins have a 360° crank throw, which makes tap­pet set­ting easy. Here’s why...

Classic Bike (UK) - - WORKSHOP -

1 Pis­tons go up and down together but fire al­ter­nately. So while one cylin­der’s in­let (or ex­haust) valve is wide open the other is fully closed, as you can see from this camshaft. This means...

2 ... to set or check the tap­pets, turn the en­gine un­til one in­let valve is fully open; the other cylin­der in­let is then fully closed, ready to check. There’s not al­ways space for feeler blades.

3 How­ever, the pitch of the ad­juster thread means that a quar­ter-turn ad­justs the tap­pet by 10 thou, so by screw­ing the tap­pet lightly home you can back off the right amount for the cor­rect clear­ance.

4 OK, this is not a per­fectly ac­cu­rate method – but it’s good enough and more re­li­able than a blade when, as is of­ten the case, there’s a mis­lead­ing in­dent in the top of the valve stem.

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.