Hitchcocks Forum

After three or more months of smooth (semi silent operation today my mystery clatter returned. Fortunately I had the iPhone on hand so could record this for your viewing pleasure. Any diagnosis welcomed, although you should know that I have checked the big end and mains, the piston and barrel, the valve seats were replaced and the rockers and tappets have been checked and rechecked. Yours in total confusion S.

http://www.youtube.com/watch?v=EOC1a3zP ... e=youtu.be

An occasional "clack", without any regular rhythm?. The rest of the engine rattle sounds very normal. Have you tried to localise the source using a screwdriver held against parts of the engine (pointed end) and the handle to your ear? - Foreign object in the primary case? Do you only hear it when ticking over or is it present when riding. Must try recording the noise of my EFI, which sounds a lot worse than your machine. Cheers TrevorCH

Hello Simon. That's an odd one! Sticking valve, perhaps? If it closes partially, then drops the last mm or so it could cause a louder 'clack.'

Or, maybe end float on camwheels or idler pinions?

Hi Simon...The very even running you would imagine would exclude the possibilty of a sticking valve or follower but perhaps it could be. Perhaps it's the oil pump worm occassionly slipping on a broken tooth/teeth but that wouldn't disappear for any period of time. As trevor suggests maybe something in timing chest that is getting picked up on the cogs, but they would soon get ground to paste or strip a tooth off one of the cogs.Other possibilties is the Auto advance retard unit or even the magneto...maybe the the bearings are very worn and occassionally the magnet is hitting the coils?

Hi Simon ------------ nothing worse than an intermittent fault, is there ?? I'm with TREVORCH on this one and would use the old "stethoscope" idea to try and pin-point it. I must say it sounds quite a solid tapping. Have a practise first somewhere else eg on the primary side but in the same area, to learn the normal and different background noises---bearings, oil slush etc. Then try on the timing side at the suspected area. On a more lighter note, it sounds like morse code !!! OO-er? Keep the faith old son.

I've tried the screw driver stethoscope but it's such a clack that it seems to come from every direction. I also thought it was a loose chunk floating in the timing case but twice I've pulled it apart to find nothing. I haven't checked the oil pump recently and that is getting to be the last man standing. I did put a magnet on a stick into the crank case to see if there was a stray nut in there but the weird thing is that despite the very menacing note and it generally starts out louder than you hear it on the vid there is no sign of metal or swarf or even any witnes marks. The only consistent aspect os that it doesn't do it cold and often does it after being restarted after a run from cold ( if that makes sense?). It sounds exactly like a sticking valve and I thought Norm had nailed it with the idea of loose valve seats which did look possible but they were nicely replaced. The other thought is that the rocker is sticking a bit and making the push rods clack but as one of you spotted the idle is even. It will no doubt reveal itself in the fullness of time but it doesn't half hose me off!

A couple of more ideas Simon. Remove the tappet cover and run the engine.....Does the "Clack" sound louder? Also try placing your index finger tip centrally on each of the push rods at tickover speed one at a time. (Not recommended if you are careless!!!!) See if the Clack registers a different sensation exactly coincidentally. (Funny, as I type this I'm getting a Deja vu sensation, not sure why) This might give some idea if the noise is valve train based. BTW, if you use the screwdriver stethoscope put an earlug in the other ear or a finger to close it. This makes a massive difference to its effectiveness.

Hi again---------Talking of sticking your finger in your ear ?/ then have a look at THIS ]----------------http://www.newciv.org/nl/newslog.php/_v ... 000061.htm -----------------------Might not cure the clatters ( here comes Franky Howard now ! ) but hopefully give you a larrff !!

For what it is worth my 2 drachma say look to the primary drive.