I have spent some time trying to diagnose noisy tappets on my M20. I have read a lot of the threads here and checked the oil feed / set the tappets etc.
Yesterday i noticed that there was no tappet noise with the chest cover off the bike that returns when its back on.
There are no obvious signs of metal to metal contact. The compression lever is set correctly. I presume the cover is amplifying the noise but is there any thing else i can check so resolve the problem ? I am running good quality 50 grade oil and there is a reasonable amount of oil in the chest.
I don't run standard tappet clearances and haven't done for years..(.010" inlet, .012" exhaust)...
I run a 'snug' .008" on the inlet and a 'looser' .008" on the exhaust...That quietens things down a bit, though you will have to check your valve lifter setting after making the adjustment...
Are you running the aluminium or steel tappet plate?...and have you followed the setting instructions for getting the cams in the correct position before adjusting the gaps?...Ian
I don't run standard tappet clearances and haven't done for years..(.010" inlet, .012" exhaust)...
I run a 'snug' .008" on the inlet and a 'looser' .008" on the exhaust...That quietens things down a bit, though you will have to check your valve lifter setting after making the adjustment...
Are you running the aluminium or steel tappet plate?...and have you followed the setting instructions for getting the cams in the correct position before adjusting the gaps?...Ian
Hi Ian, what is the reason for adjusting the tappet clearance that way ? Especially the exhaust is 50 % less :worried:
Cheers
John
To cut down on mechanical noise!...I took the bike out and gave it a good thrashing to get it fully up to working temperature...I then immediately took off the tappet cover and checked the gaps on returning home...
Both tappets were not far from the 'cold' clearance so I thought it worth a gamble to close them down a little as an experiment..That was at least 15 to 20 years back and as I didn't encounter any problems I adopted the new settings as 'standard'...
I think Mick from Draganfly actually runs his a little closer than I do at about 6-7thou.
The subject of differences in tappet settings for different engines that are essentially the same structurally and that share similar operating temperatures etc. would bear some discussion I would say....Ian
Ian, a manual from publisher bruce main-smith tells me that the 1937-38 m20/21 had in .004 and out .008 and the 1939/40 m20/21 had in .008 and out .0012
Why the sudden difference, special the the inlet clearance.
cheers
John
Might the difference have something to do with the cams? Did the pre-war bikes have the same type of overlap valve timing? I know when the post war C11 engine changed from the first type cams to the "ramped" cams, the clearances became much greater. Ron
