Having had the barrels of my 850 mk2A rebored I've spent the weekend trying to get her back together again. The engine is still in the frame and I've been working on my own so it has been a bit of a faff. Having gotten the cylinder head on I turned the engine over on the kick start to check the valves were operating and noticed something odd. Occasionally, but not always, I get a sharp clang from one of the inlet valves. On closer inspection what i am seeing is that the inlet valve starts to open normally and then slams closed again ( causing the noise) before then reopening and carrying on as usual. As I say, it doesn't happen every time I turn the engine over. Can anyone suggest what is going on please?
Regard to all
RichardP
I had the same fault. it was…
I had the same fault. it was a binding tappet block binding in its bore. cam moved it up , spring force then delayed to push it back to the cam. A delay a big gap and a slap down to its right home. .
pour some oil down push rod tunnel, push down on rocker, Keep doing that until it drops by spring pressure
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Did you leave the cam…
Did you leave the cam followers in the block when you had it bored? If so they will need removing and cleaning. Did you thoroughly clean the block before fitting?
Are the pushrods located properly in the rockers?
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Thank you all
For your suggestions. My first response when I encountered the problem was to remove the head again and to check the push rods - they are indeed straight. I then took extra care to ensure the push rods were properly located in the tappets when reassembling. No change.
I did leave the tappets/cam followers in situ when the barrels were rebored but removed and cleaned them post event. I thought I did a good job with the cleaning but perhaps not....
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hello, are the tappet…
hello, are the tappet adjustments ok. barry
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They are set roughly at present
I plan to set them properly this evening as one of the measures.
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That sounds like the rockers…
That sounds like the rockers aren't located in the cups on top of one or more rods. Use a torch and bent wire to located them and don't let them escape as you tighten the head down onto the valve springs.
Unless something such as a collet has escaped...
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The push rods appear to to correctly located on the rockers
I found that a magnetic telescopic pointer works really well to position the push rods. The rods are aluminium but the caps are steel and so can be positioned with a magnet. Tonight I will check the collets. Thanks to everyone for your comments and suggestions.
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David was right
I have to own up to two errors - firstly I meant to write that it was an outlet valve not an inlet valve that was clanging. Secondly I thought I had roughly adjusted all four tappets - I hadn't. When I checked this evening I had set three of the tappets but not the fourth. On the valve in question the adjuster was wound right back thus allowing the push rod cup to come out of the rocker.
Thank you all for your help.
Regards to all
Richard P
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Is the Push rod catching on the edge of the cam follower but then drops down into its proper position? One then asks the question why/how does the pushrod sit on the edge of the follower in the first place? Bent push rod? Pushed out of place by the head gasket?
If the push rod where sitting on the edge of the cam follower at some time then of course the tappet gap could/would be mis set?