Tappet servicing
 

Ey up

Had that age old symptom of a rattly engine a while back, and so after reading manuals and seeing posts on here fingers were pointed at the cam chain tensioners. So they were checked the other weekend , tensioners seemed to be working fine and springing back as they should, and were put back in as described. A slight "clunk" from the engine was heard, assumed to be the cam chain guide popping back into place. Fired up the engine, result (I thought) as the rattling had gone.

Not quite. Couple of hundred yards down the road and that ruddy rattle is back. (Seems to come mainly from the front pot just for info)

Upon browsing the manual again, it seems that the tappets should have been checked at 15,000 miles. Hmm, that was about 5,000 miles ago me thinks. I know that it wasn't done back then as there didn't seem any need to with the engine running sweet at that time.

So long and short, would I be right in coming to the conclusion that the tappets need servicing and possibly a change of shims and that these are the source of ye olde rattle?

Unless you have really *abnormal* wear somewhere in the valvetrain, valve clearances will generally tighten up, not get looser. With cams acting directly on buckets over the valve stems, there's not a lot of scope for wear, except in the cam lobes (which shouldn't), the bucket faces and the valve seats. Wear in the valve seat causes tightening of the clearances. I've been a naughty boy: my curvy's done over 25K miles now without checking the valve gear. I have been meaning to, honest!

I was under the impression from the manual that the shims would wear, and that'd rattle.

Hmm, so is this here rattling of mine more likely to be requiring me to have another pop at the cam chain tensioners?

Hmm, you might be right. I'd wrongly assumed that shims always live *under* buckets. Seems they can work either way - either above or beneath the bucket. I thought the cams had to come out on an SV to shim them, which always implied to me that they were underneath the bucket.

The shims don't wear.

I was under the impression that if the engine gets quieter then the valve clearances do need checked. Not that it is a good method to use if your valve clearances need checked but something to think about. I'd be more inclined to say something was 'wrong' with the cam chain/tensioners.

In the sv the shims are under 'buckets'.

Take another poke at the tensioners/cam chain. Might be worth turning the engine over via the non-turning-engine-on method to see if you can hear any abnormalities.

Shims are made of fairly hard metal, and live a fairly easy life. Valve seats, and many other parts of the head and valve train are likely to wear faster meaning clearances can close or open up. I think it's worth mentioning how tight these tolerances are, "listening" for valve clearance adjustment is not wise. I changed 11 out of the 16 shims on my ZX6R at 12,000 miles and can say the engine sounded and felt exactly the same after the work. It defiantly needed doing though!

Again with the noise I'd be thinking of a cam chain tensioner, but if you've checked it and it's defiantly fine some more investigation may be needed. If you do need a new one do a search, the SV engine is on it's 3rd (or more) revision of this and some are backward compatible. So might be worth replacing with newer parts if a replacement is needed.

Jambo

What's the opinion on manual cam chain tensioners then? Those automatic cam chain tensioners seem a bit poo to me.

Hmm... This is all very interesting to me. My curvy is approaching it's 7500 mile service. A call to my local friendly mechanic (Speed Superbikes, Exeter. Winner - MCN Dealer Of The Year 2006) yielded the response;

"About £250 for the service. But when were the shims last done?"

"No idea." I replied. "I don't have the service book with me."

"Well," came the response, "if the shims need do-ing then that'll be a lot more time"

'Shims need do-ing'? Do what exactly? If they we're refering to a valve clearance check/adjust then fine, but from what I have learnt from searching this forum and from this topic the shims should rarely need attention?

Also, £250ish for the 7500 interval? Pricey?

Is your bike still under warranty?If not I suggest doing the service yourself,or at least the majority of it.Changing the oil and filters is very easy,and will cost you about £30 while checking the valve shims is also fairly simple.It's only if you discover that they need re shimming that it gets difficult,and I would advise having that done by a competent bike mechanic.The rest of the service is largely "check and adjust"stuff and is also pretty simple.Do what you can yourself,and only put it in a garage for what you can't do.