2001 '800FI-Y hesitates upon acceleration, then clears and goes like a train :)

Hi all. I'm new here, so in a moment I'll head over to the introductions board, but for now, I wonder if you learned folks I get be able to help me out a little...

I have the above machine in Candy Tahitian Blue, love it to bits. But, on increasing throttle from cruise, say to overtake something or gently accelerating off a junction in pretty much all gears, it will hesitate/bog down for about a half a second or a second. The induction note will change as the throttles open, and it farts about briefly, then clears up completely, usually at about 5k, and then it goes like a train all the way until I chicken out and change up! It does it regardless of whether I blam the throttle open (bad idea this time of year!) or wind it on slowly.

I've searched in here for answers, but to no avail. I've checked the throttle pot resistance, and it sweeps nice and smooth from about 4.9k down to about 800 ohms, and I've had a plug out, and it was bob on. Light brown, excellent condition. Bike is really straight, one owner from new, clearly been extremely well looked after as the service history is a thing of exquisite beauty.

I've also checked the fault code memory - none stored; the FI light just glares at me when it jumper the connector and key it on...

Any ideas?

Thank you for your time.

Ed.

 

Welcome aboard.

I'm gonna go with a real simpleton approach here - and I doubt that its your problem - but what kind of RPMs are you running at? The VFR is well known for not wanting to be lugged at low RPMs. While everyone has their preference at what they like to ride at (I'm seldom below 4000), if your trying this from say 2500rpms, that's really way too low.

I know you said once she gets to about 5000 she clears up.

I could be entirely wrong, which happens pretty often, but maybe you're just dumping too much gas into her at low RPMs before she's ready to move?

Could it be something that simple?

 

Um, yeh it is at low revs. I'm a recent convert to bikes, and until recently have been driving a V8 petrol and a TDI, so I do cruise at low RPM... Perhaps I just need to let it Buzz a bit more?

I rode a friends baby blade, and she told me to keep it above 8k...! Hellfire!!!

Above about 5-6k, it doesn't stutter at all.

Perhaps it's operator error?!

Guess I'm a bit surprised that a supposedly torquey motor like a v4 doesn't pull well low down...

 

I'm still not saying I'm right, but I'd definitely try to keep those RPMs up a little bit and then see what happens. Yes its a V4, and yes its "torquey" (sounds like my Puerto Rican wife trying to say "turkey"), but its not a miracle worker. I'd say try your usual route, but keep the RPMs about at least 3000, preferably 3500, and report back.

 

I have had my 2003 about a month and I had the same complaint in the beginning. After reading a lot of the threads, I got a used PowerCommander III USB, blocked the PAIR valve (maybe just a US emissions device) and added O2 eliminating resistors (again US catalytic converter). Not it is not as recalcitrant at low RPM and smoother starts. Makes life much better. Still ride above 3K RPM, but doesn't complain nearly as bad if you pull from 2K-2.5K.

 

These motors are full of torque...but they are setup to come in around 5000 rpm (ie mid thru upper rpm torque). Honda used to put the VFR750 motor in the Magna cruiser bike but it was re cammed for low to mid rpm torque.
Run her up to around 7000 rpm in first gear and snap that throttle....you best be holding on!! :vtr2:

 

Get a power commander III and it will smooth out all the low end problems. I had the same problem on my 01 and it cured all my issues.