Hi. Thanks for all the replies and ideas.
I plan to work on the bike this weekend and will take some pictures of the holes in the lifter body tops and try and post them here.
During the last time I changed the pushrod corks, we found that the front exhaust lifter top had come loose in the body.
At first I didn't know why the top of the lifter was wobbling around when I was lowering the adjuster.
When the pushrod had been removed I pulled the lifter up as far as I could in the body to try and see what I could.
The adjusting top of the body came out in my fingers.
Since I did not know about any other problems with the Eastern lifters, I just assumed it was a fluke anomaly.
I removed the lifter block from the engine case and had a look at the lifter body.
Although the lifters were still nicely fitted in the lifter blocks, the top of the lifter had become a loose fit in the body. Also the top was not concentric with the body. If the top had vibrated around in the body, it would have jammed under the vacuum port in the side of the lifter block with some disastrous results.
I actualy know this could happen because I put it back in and gently rolled the engine over with the back wheel to back the next lifter down so i could take out the pushrod. At first I could not work out why the engine would not go through a revolution so I backed the wheel back a bit and gently came forward again and it came to a gentle solid stop. I rolled the wheel backwards and pulled the top of the lifter out and then rolled the engine through.
I cleaned up the loose lifter with acetone and used a loctight product that fills a gap of a few thousandths and lightly nipped it between the soft jaws of the vice for 24 hrs. It ran marvelous during a recent ride, but ,I am now feeling I might look for another set of lifter blocks and move to another brand of lifter. Iwill let you all know how it goes.
Regards Steve Little.
Race Frame Engineering.