VFR 800 6gen - rough engine under 5500rpm

Hi
- I'm looking for help with my VFR 800 VTEC 2002, 80,000 km, I've owned it for 3 months. I'm looking for advice.

My problem is how rough and "unhappy" my engine runs from 3000 to 5500 rpm. I can hear it especially when I open the throttle. and I feel like I'm riding a big single cylinder. I feel the problem especially at high gears.

The engine starts nicely, idles well, runs great above 5500rpm, VTEC works.

I tried disconnecting the PAIR system, it partly improved the engine performance.

Has anyone encountered such a problem?

Thanks for any advice.

 

Have you tried balancing the starter valves? What condition are the spark plugs?

 

- the current spark plugs are not new, but the gap is fine, dark brown, they look good..
- at the moment I haven't tried to balance the starter valves, I'm waiting for a new vacuum hose, and I want to replace them

 

Has it been running on old fuel - e.g. after long storage?

 

Fit new NGK plugs then reassess

 

- i bought this motorcycle in the spring, as "non-runer"
- it have electric isues, burn positiv wire, burn fuse box, burn starter solenoid conector, front brake issues, clutch master cylinder is leakink..., tyres, frort fork seals
- i fix all that, and drove 1500 km on his motorcycle
- all is ok, only one thing bothers me, that rough engin charakter pod 5000..
- i never ride VFR before, i drive in city - 50kmh, for smooth engine i need have 3 gear and 4500rpm... and that feels a lot to me...
- my other bike, GSX 1400, in city i ride in 6 gear and 1500rpm, and engine accelerete beautifly
- what engine revs do you drive in the city???

 

I have no experience with the fuel injection system so my knowledge is rudimentary at best but "electrical issues" may have damaged a sensor (pressure, temperature, throttle position) or the controller. The manual describes a way to interpret signals from the "FI" dashboard control light. The manual also describes a "Variable Air Intake" system which activates around 5500 rpm. Observing the "FI" lamp would be a good place to start.

You seem to be from Slovakia where there are some elevation differences. If the issue is related to a malfunction of e.g. the pressure (MAP) sensor the issue may also depend some on where you are (heightwise).

VFR driveability: I have an older model. I consider it very smooth also for use in city from around 2500 rpm depending some on the traffic.

 

Did you replace the air filter? If not You could test how she runs without.

 

- I have an old air filter, I cleaned it with a air compressor after buy
- I did an experiment, I removed the air filter, I feel that the engine worked a little better when accelerating from low revs (3000), but it was not a significant change.
- in the spring I took out the snorkel, Pair valve delete and did make "flapper mod" - that was a noticeable change for the better

- I have no FI errors
- in service manual, page 5-14 to 16 i some MAP testing procedures, i will try them

 

If I were you I would take this advise as well. Theoretically, if the MAP sensor was dead, the FI light would tell if you do a diagnostics.

 

another question:
- in manual 9-23, I found a "primary drive gear" with three springs, which is connected between the crankshaft and the clutch, its purpose is to dampen the engine pulse? it could be a source problem?

 

Will have no effect on your problem. Springs and split gears are to minimize gear mesh backlash.

 

Hello, I added an additive to the gasoline to clean the injection nozzles, after driving another 1000 km, the engine is finally running nicely.

Thanks for help.