Tappet adjustment

[jon w]

Strange one on my 61 CSR, not sure if anyone has encountered this.

I've ran out of adjustment on one of the exhaust valve tappets. The other three are fine and around mid adjustment.

When the engine was built, the push rod lengths were checked, as was wear on the followers. The rocker looks ok, so I'm stumped.

Any ideas much appreciated.

[JimFitz]

I had exactly the same problem. The answer is to grind a little off the top of the relevant valve stem. The valves could have had the faces ground in the past which would reduce the clearance. A mate did it for me on a valve grinding machine but I would imagine it could be done on the platform on a fine grinding wheel as long as the valve top is kept square. Obviously be careful you do not take too much off as there is no going back!

Jim

[robcurrie]

You could measure all the pushrods and put the shortest one in that position, it might work out without changing anything else.

Rob C

[jon w]

I had exactly the same problem. The answer is to grind a little off the top of the relevant valve stem. The valves could have had the faces ground in the past which would reduce the clearance. A mate did it for me on a valve grinding machine but I would imagine it could be done on the platform on a fine grinding wheel as long as the valve top is kept square. Obviously be careful you do not take too much off as there is no going back!

Jim

Cheers Jim.

Only issue is that mine is the other way. I can't close the gap enough!

[SPRIDDLER]

When the engine was built,...........

Has th'engine been run after being rebuilt?
Have you ever run th'engine or ridden the bike?
Was anything replaced when th'engine was built? Perhaps a new valve seat or valve guide has moved or was fitted incorrectly.
How excessive is the gap? - A few thou? Quarter of an inch.....?
Maybe the valve is stuck open.

It's difficult to say, not knowing what we don't know

[JimFitz]

Ah, that makes it a little more awkward.
If you have had new valve seats fitted then perhaps one has been not cut quite deep enough or pessed fully home. I am assuming that you re-used the old valves and it may be that one or more of the valves has had the end ground down in the past but without removing them and measuring the length it would be difficult to tell. It is strange that you have a good adjustment on the other three.

Perhaps another member can advise the correct length of the valve and at least you will know where you are. If it proves to be too short then it could possibly be built up with weld (stellite?) and ground back or a new one obtained of the correct length.
What size gap can you adjust it down to at the moment?
Were all the pushrods exactly the same length when you checked them?

Jim

[jon w]

The gap is 0.3mm, it should be 0.2 (sorry I do this in metric). I dod re-use old valves and will look for grind marks on the top. The valve seats all looked fine and the push rods were the same length. You idea of stellite building one end may be a good temporary measure. Cheers.

[jon w]

When the engine was built,...........

Has th'engine been run after being rebuilt?
Have you ever run th'engine or ridden the bike?
Was anything replaced when th'engine was built? Perhaps a new valve seat or valve guide has moved or was fitted incorrectly.
How excessive is the gap? - A few thou? Quarter of an inch.....?
Maybe the valve is stuck open.

It's difficult to say, not knowing what we don't know

Yes the engine has done nearly 400 miles and pulls like a train. The heads are tight down to the correct torque. Strange thing is that it was fine when built. Seems like something has settled.

[hwilkinson]

Could one of the pushrods be bent ?

Harry

[1608]

You can remove a push-rod without removing the head. I would go with the bent push-rod as it seems all was ok when re-built. Theres not much else that could have altered. To remove suspect push-rod, get the relevant cylinder on tdc. Then carefully remove the rocker spindle clamp and slide the rocker spindle to one side. Be very careful when removing the rocker arm not to drop any shims or sprung washers etc. Replaced all my brother's this way, as they were alloy racing ones and tappets constantly needed adjusting. please give an up-date.