Hello I have a problem that I hope someone on here will have the answer to, when I gap the exhaust tappet, it appears to be set at the correct gap but if I spin the collar that gets lifted by the decompressor spindle the gap is all over the place, one minute the feler gages fit nicely and then I turn the collar 180 deg the gap has closed to virtually nothing. Something must be bent but I'm not sure what, I've fitted a new tappet head because I thought that had been hit by the decompressor spindle but the new one has had no effect, looking at the inlet, this gap also open and closes when I spin the nut.. Do you think the pushrods are bent?
Also on the tappet spindle the part that lifts the collar should that be perfectly round
Thanks Alwyn 😩
The problem you have is bent cam followers, more correctly called tappets...(the part that the tappet head screws onto...) A partial (at least) engine strip down is required to replace these parts..
However, it is possible to straighten them in place WITH CARE...
As an example, to do the exhaust side...Set the engine so that you have tappet clearance. Disconnect the valve lifter cable and then remove the valve lifter spindle and its housing from the barrel..They are removed with a 20mm spanner...
You will now be able to rotate the cam follower and tappet head and you will see where the 'runout' is...Turn it until the bend is facing you and then, using a brass or aluminium drift and a hammer give the hexagon on the tappet head a light tap...
Check to see if the runout is reduced after each tap and adjust the force accordingly, using the minimum force possible to straighten the follower...
It sounds a bit brutal and care must be exercised rather than going at it too enthusiastically, but this method does work...
The flange on the exhaust tappet head should form a complete circle...Any damage is usually caused by attempting to remove the barrel without first removing the valve lifter spindle assembly
The peg on the valve lifter spindle is also completely round when new...Setting the lifter can be a fiddle as there isn't much to play with dimensionally between working and not working. Particularly when the exhaust valve seat is worn, which drops the valve further into the barrel, people grind a bit of the peg to restore some clearance...Ian
Thanks Ian, I'll give that a go at the weekend, do you think I'll be able to straighten the inlet useing the same method only striking the inlet from the side?
Alwyn
