Over Rev

[hackers2r]

I've done this 2 times by complete accident.  Here is the scenario.  Reving through 2nd but shift to 1st instead of 3rd.  Both times, the wheel hasn't locked up, and bike runs fine afterwards.  Bike is S2R 800.  I know it is bad to do this but is there any damage possible?  Wouldn't I hear and feel it running different?  Thanks.

[NAKID]

No such thing as an over-rev on a desmo engine...

[Howie]

Your bike will blow up in a week.  I'll give you a dollar for it

Seriously, you would need to pull some tremendous RPM to do any harm to the engine, like maybe shifting down at redline.  Even then it would probably survive.

[Raux]

doesn't the 800 have the APTC clutch? if so, that's what saved you.

[stopintime]

doesn't the 800 have the ATFP clutch? if so, that's what saved you.

APTC  yes it does. Does it really work? Apparently

[Raux]

did you notice that was at 11pm 

[booger]

Yeah but doesn't the rev limiter take care of over revs? I've bounced off of it once while in first.

[Raux]

no it takes care of fueling. it's a fuel cut off, not a rev cutoff.

[Howie]

Yeah but doesn't the rev limiter take care of over revs? I've bounced off of it once while in first.

If the over rev is due to the engine being driven by the rear wheel, due to a downshift at too high an RPM, no.  The APTC clutch helps keep that from happening.

[yotogi]

Yeah but doesn't the rev limiter take care of over revs? I've bounced off of it once while in first.

The rev limiter will keep you from using the engine to pass the readline. On a bad downshift, the rear wheel can be driving the engine past the redline. The only way to prevent that is with mechanical intervention. Hence, slipper/APTC clutch. You got one.

As I understand it though, it is difficult to over-rev a desmo engine as you have mechanical valve closure instead of spring closure which should prevent the valves for getting thrashed by the piston. I imagine that you could do it if you really tried, but to do it accidentally by dropping a single gear would be a real challenge.

[hackers2r]

This is what I understood also.  Just making sure.  Thanks.

[Keld]

As I understand it though, it is difficult to over-rev a desmo engine as you have mechanical valve closure instead of spring closure which should prevent the valves for getting thrashed by the piston. I imagine that you could do it if you really tried, but to do it accidentally by dropping a single gear would be a real challenge.

Over rev is not all about the valves. it stresses the crank, piston and rods too. If it was all about the valves hitting the pistons,  there would be no need for a rev limiter on a duc engine.

[scduc]

Personaly, I believe that everyone should hit their rev limiter at least once to know how the bike reacts. I was scared to death to find out, but once I did, it was no big deal. Some have said it feels as though the brakes are thrown on. Mine felt like I let off the throttle and just leaned forward a bit.

[Raux]

based upon some calculations and limits given by a noted Ducati Engine builder you can figure that the max theoretical rpm before things start flying apart for the 800 with the 66mm crank is about 11591rpm and the safe rpm is about 10500rpm

don't quote me on it (as my calculations may a be a little off) and i'm certain it depends on the build of the motor, valve specs, etc. as to whether you motor is capable and safe at those rpm's.

but those are specs for  some race bikes i've been told.
the stock bikes obviously have a fuel cutoff way before that.

a cool thing for me, IF i keep the 57.2mm crank for the 696, are limits of 13375 and 12035 respectively.

[yotogi]

a cool thing for me, IF i keep the 57.2mm crank for the 696, are limits of 13375 and 12035 respectively.

Whoa... 

I can only imagine what that would sound like!