I've been thinking of getting a track bike (not to race, just to have fun and improve my skills), and I'm seeing what I think are some good deals on 996 and 749S. I think that I can get either for about the same price. I realize that these are two way different bikes, but I think that at this stage I can adapt to either.
The 996 has the older Desmoquattro heads, and the 749 has the Testastretta heads. Are the newer heads less prone to flaking rockers?
I've been told that the newer heads are easier to maintain, is the difference *that* significant?
Now that I've conquered adjusting the valves and replacing the belts on my 2V engine, I'd plan to do my own maintenance on the 4V as well. I'm thinking that I shouldn't need to check/adjust the valves more than once a year, assuming 10 or 12 track days. One consideration would be how much I need to invest in special tools, is there a large difference in how many new tools I would need given the differences in the two heads?
I've ordered the Desmotimes book for the 4V engines, I assume that will help me answer some of these questions when it gets here... but in the meantime any help is appeciated.
749S has 6mm valve stems, and uses special taper-seat collets.
emsduc.com does not make shims for them.
AFAIK, it would require substantial investment in special tools.
The Testastretta heads seem to be less prone to flaking rockers, from what I've seen and heard.
There's other folks here that know a lot more about 'em than me, so YMMV.
In some ways, the Testastretta head is easier to work on, in other ways, not.
Mostly just different from the Desmoquattro.
The 996 uses the same shims as the 2V 1000, so you're familiar with the size of 'em.
Access to the valves/shims is quite a bit more restricted than on the 2V engines, and on a SBK, you've got to take a lot more stuff off to get at 'em.
Also, there's twice as many to do....
QuoteAre the newer heads less prone to flaking rockers?
Not really a head qustion as different production years of rockers. 2000-01 were bad batches.
the first bikes we saw it on were around '99 models - st4 and 748 especially, but then 996 as well and older 916 models. no consistancy that i could see for use, maintenance, etc. we saw a few older bikes do it - 851 even, but much more of the later ones. we had some guys with st4 who had really bad runs with them, doing cams as well.
Good thing about buying a 996 is that a lot of them already have the megacycle rockers that bypass this problem.
My 996 is my track bike and I love the shit out of it...
Quote from: brad black on December 08, 2008, 03:32:16 AM
the first bikes we saw it on were around '99 models - st4 and 748 especially, but then 996 as well and older 916 models. no consistancy that i could see for use, maintenance, etc.
Over the last several years, I've come to the understanding that the desmoquattros which were more prone to flaking rockers were from '96+. The '95 and earlier bikes have been known to have an odd-ball every now and again, and I've seen/heard of flaking Testastretta rockers, also.....but they are quite rare. Heck, my 2002 748 had four rockers replaced at 5600 miles during the first valve adjustment.....I have a set of heads from a 1998 748, and every single rockers is shot.
Interestingly, the clearances were huge on my 748 at the first service, and when the valves were done, they were all placed in the middle of Ducati spec. I would up changing 14 out of 16 shims to do this (all 14 were out of spec). At 12k, all vlaves were still in spec, most hadn't changed at all, and the rockers looked no worse than when I checked them at 18k. I currently am sititng at 18k miles and need to tear the bike down, but I've had too many other projects going on to get into it, yet. I'm hoping to tear it apart in the next month or two.
FWIW, both of my S4R's (both 2004's, 996/ST4S motor) had at least one flaking rocker @ 6k
Adam
my S4 had 5 openers dud at 5000miles I replaced all 8 openers with Nichols /Megacycle rockers.