Jumping revs vfr 800

The problem appeared overnight. Saturday was driving perfectly, but Sunday morning the problem reappeared. It behaved normally three times, the idle was stable, and I drove. If it starts, that's the cause. It only started with the hood open, where it immediately revved up. I've never seen a similar problem or such a variable idle anywhere else. The fuses are good, the pump is turning on, and nothing was done before the problem occurred. Does anyone have any ideas or have seen such a high idle?

Best regards.

 

What is "the hood" that you referred to being "open"? Upload a photo of this "hood" please.

 

I'm using a translator. Maybe he did something wrong. What I meant was that I could only start it by opening the throttle, meaning I opened the throttle, and when it started, it would rev up. Otherwise, it wouldn't start. He couldn't maintain idle speed because of that in the video. You can see the revs jumping around; they're very unstable.

 

check for any air leaks or hoses that are loose in the throttle body area.

do you have a service manual for reference ?

 

Thanks for the clarification.

What year is this VFR? How many km on the clock?

Is there any difference between a "cold" engine start, and a "warm" engine start?
In other words, does the bike idle better when it is either cold (been off for an hour or more), or when it has been running and is warm?

 

I have the manual, and I haven't found any disconnected or damaged hoses. It's a 2002 model, with 72,000 kilometers on the clock. It doesn't matter if it's warm or cold. The revs fluctuate, except for the two times it ran properly, and after shutting it off, it started perfectly and maintained idle speed. It did this until it cooled down completely and ran again, as in the attached video. I wondered if it was the valves, but the problem occurred suddenly. Anyway, if I can't find a solution myself, I'll be taking it to a mechanic in three weeks, as I'm out of ideas, and I don't know if something strange happened to the engine. When the problem occurred, I started hearing a sort of knocking sound coming from the rear cylinders. I don't remember hearing that sound before. There was nothing alarming before. Now I can't even start it.

 

You cannot start it with the throttle wide open anymore?

Is there sufficient oil in the motor? If so, I would pull a spark plug or two in order to see if they are flooded with fuel or not. while they are out check the compression in each cylinder, Insert a spark plug into the spark wire boot, ground the plug, and turn the engine over to see if you have a spark.
The engine needs the correct mixture of fuel and air, a correctly timed spark, and sufficient compression in order to run. Are any of these missing?

 

^^^ i agree its time to inspect sparkplugs, looking for one that looks different from the others.

symptoms suggest one cylinder is firing irregulary. when it fires correctly, rpms jump up. could be a bad connection or failing ignition coil on one cylinder or...........

worst case, could be a bad CDI ign black box.

 

Only three coils, because I can't remove one bolt securing the fourth coil. The Allen key socket is worn out. I used the old spark plug; there are new ones installed in the engine. I'll remove them as soon as I have time. For now, I'm packing up the job. I don't know if it's correct.

 

first, replace that plug with new or use anothder one for testing. next, check both resistances on that coil, primary and secondary, and compare both to known good coils and service manul specs.