650 Mercury pushrods length

Hi, the commando ones are longer. You pull the ends off and file to suit the old ones. I believe the commando ones are 0.032" longer. I bought new ones for £25 in America on eBay. Best regards, Paul

It is all down to the engine number that you have. After engine and frame number 125871 the valves are longer and the pushrods areshorter. As you have a Mercury your engine and frame number should bestarting from 129*** so you can use Commando inlet and exhaust valves and also Commando push rods. The idea behind the change was to change the rocker ratio, and this was supposed to give may be 1 to 2 bhp more. All the parts books from 1966 onwards show this. Under the heading of Tappets and Push Rods on page 6 of the Master Parts List for 1966-1967-1968.

The inlet valves for your Mercury will be a smaller diameter that the Commando valves, but the exhaust valves are the same size. The point is the valves were made longer, and this is a very distinctive feature of the later engines after 125871. You can also fit the later valve guides so that an oil seal can be added to the inlet valves. Mushroom tappet adjusters are alsoupdrade to fit if you have to take the cylinder head off.

The inlet valves for your Mercury will be a smaller diameter that the Commando valves, but the exhaust valves are the same size. The point is the valves were made longer, and this is a very distinctive feature of the later engines after 125871. You can also fit the later valve guides so that an oil seal can be added to the inlet valves. Mushroom tappet adjusters are alsoupdrade to fit if you have to take the cylinder head off.

Are you quite sure the problem is with the pushrod? Most unusual, I would normally look at the valve - seat recession perhaps?

Previously wrote:

Complete head job with new valves, seats and guides1000 miles ago. Odd that only one exhaust rocker gap has increased.

But have you actually measured the pushrods? Not convinced the pushrod is at fault. Gordon.