What's this change in engine tone ?

VTEC, 2003, 32000km ( 19,900 mi ) on the odo.

On a couple runs now I've 'sensed' a change of 'beat' after :
- been running for awhile ( engine at least 75C or hotter )
- throttle held stable at one 'cruise' setting for a period, around 5000 - 5500 rpm ( typically in 5th gear )

I 'sense' ( but not sure if I can 'feel' a surge or not ) the motor tone changes slightly, YET, if I tweak the throttle it's not stuck in a dead spot nor slow to respond ie will move outa this 'notch' when required to.

I don't think I'm imagining things ... however, I've not done enough runs yet on this machine to know for sure.

Any comment from experienced 6th generation Viffer owner(s) or engineers ?

 

No viffer 'engineer' by any stretch of the imagination so I'm just taking a stab in the dark based on the rpm range you've stated. It may have something to do with the leaning out of the fuel/air ratio for emission requirements.
On the stock fifth gens we have a short flat spot just after 5000 rpm. Maybe this is what your picking up on.

Sorry mate, thats about all the best I can offer - over to the guru's!:biggrin:

Cheers,

Skid

 

I notice a slight flat spot around 5k-ish on my 2002 as well. It is most noticeable in 2nd or 3rd gear where you can feel it more. Any other 6th Gen'ers notice the same?

 

That's Honda trying to save you gas. There's an exact explanation up on here somewhere. It has something to do with 'stoimetric' so search for that.

I've installed the Power commander Oxegen sensor eliminators which is supposed to stop the bike from leaning out when cruising. I guess there's a $2 radio shack part that does the same thing. The power commander helped too.

 

Had a 6th Gen with a slight flat spot on cruise in this area as commented already, it was due the the closed loop system and 02 sensers leaning out the fueling lowing exhaust emissions, may be the cause ? some have got overcome it with o2 eliminators and PC3...

My now '99 Gen5 has no noticable flat spot as the 02 sensors and CAT weren't introduced in the Klingon until the '00 model update.

 

Thanks mate ! Interesting, so it's probably not my imagination afterall.