Hello again to all. Its been a while since I had to post ( A7 with starting problems, but traced to magneto and put right by Groily for me - 700 trouble-free miles since...many thanks ). Out on Saturday poodling round the lanes when I thought I could hear a knocking from the front of the bottom end, not a rhythmic, every revolution kind of knock, but occurring randomly and without any sort of pattern. Limped home carefully, and felt around the front end and dynamo, where I convinced myself I could feel something knocking. Switched off, and called my more experienced mate, and we did the ' mechanics stethoscope ' trick with two big screwdrivers, although by now the noise had stopped. All we heard was tappet rattle !
Anyway, took the inspection covers off the rocker box this morning and checked the clearances. Both exhaust valves were within a couple of thou of 16, so re-set those. Left inlet was still on 10, but right inlet was about 1/4" .....!!! Oh, oh. I had to screw the adjuster down so far into the rocker to get to 10 thou clearance, there was no thread left to put the locknut on. It was not like that when I put it together, and all rockers and pushrods seem to go up and down as they should. I put new valves and guides in when I built the engine last year, new alloy pushrods from Brit Only in Austria
( got fed up with people in this country telling me that A7 rods were the same length as A10...).
Right inlet valve does not appear to be sticking, and returns the same distance as the left. Spring pressure feels the same on both valves. My problem is this: the bike was running okay until I heard this odd noise, and now there seems to be something definitely not right. Other than perhaps a sticky valve, or a bent pushrod, what other disasters might I discover ? Disintegrated cam follower ( do they do that? ). 1/4" gone off the bottom of one of the pushrods ( don't think they do that either, do they ? ) Catastrophic failure of the cam shaft ? Then I guess the engine wouldn't run at all if it was the cam ( new 357 cam, iron head, 1959 model). Certainly 1/4" seems to have disappeared from somewhere, and I am at a loss to explain where it has gone ( maybe the wife has got it, she's always complaining about an extra quarter of an inch !!) If I have to take it all apart, then so be it, but I though I would ask first before getting the spanners out. Anybody with any similar experience out there, please?
ATB
Norman