998S Broken Valve Collets
 

Hi
Just had the race bike in for its second year service. Would have done it myself, but wanted to ensure I got my annual stamp in the Service Book.

Response was that I've had a number of broken valve collets, and that this is *apparently* "common" with the Testastretta engine.

Does anyone else know of this? Is it just because it gets a hard life from me, or is this really common on road-bikes too?

Bike has 5,800 miles, only about 300 of which are race miles.

Any information would be welcome.

I'm sure i've read somewhere that this is common on engines that spend their entire life near the red line! Some American web site offers special collets that are claimed to reduce the problem. Cant for the life of me remember the name though.

Does the 998 still use the half rings as valve keepers? It's quite common for them to break and you're supposed to replace them whenever you change a shim. But, even if the break it's usually not a problem as it can't fall out. Their only about a quid each, I think.

Nelly will know more...

Oh, and to refresh Paul's memory:
MBP valve collets
JHP do them in this country. I've looked into it seriously for my race engine, but (1) they are quite expensive, and (2) you need to machine the shims to fit on the 4 valve heads. So reshimming becomes a problem unless you also buy their special shim kit. I passed.

[Edited on 17-3-2004 by Felix]

I think they also claim that service intervals for valve timing can be increased.
I'm not sure if that's a good thing or not?

Cheers guys, thems the ones! I remember the claim of increaced adjustment intervals as well.

Have also heard of this, not just on the Testastreta models, I believe that there are better replacements available that are better than the crap factory ones.

Before getting my 999 engine tweaked I was speaking with Pro-Twins. They advised me that they had suffered several collet failures and recommended as a result a change to a stronger items. They sell them at £18 per half (!!!). They expect a seasons wear from them.

Sigma eventually did my engine work and Neil's opinion was leave the standard ones in. He prefers to have a "soft" link in the chain to take out any stress reducing potential wear and damage to other components. Regular inspection should avoid any unnecessary engine failure.

I also believe that the collet failure is only apparent on engines ran continually at high rev's (and) with a higher rev limit.

My 998r has just had its 2nd annual service and 8 of mine needed replacement, I was told its not a problem for bikes that are ridden normally but that if the engie spends a lot of its life at higher revs The rings can snap. I took it as acompliment that I use the bike properly!

dave

As God & Dr"T" intended Dave!;)