Low power full throttle mid rpm

[Gnasher]

Hello again everybody, a few days ago i completed my driving exams (hurray) and took my bike for spin. It was amazing as it should have been, but i ran into some problems (as it shouldnt have been). At around 6.5-8k rpm at full throttle the bike seems like it almost cuts fuel off. Then at 8k right at the power band the bike flies all the way to max rpm. It seems to happen at 2-3rd gear, too scared to try first and not enough space to go 4+ gear  :o .

This could be alsorts, from stuck cold start valve/s to pin hole/s in a diaphragm, air leaks and possibly blocked or restricted pilot/main jet fuel circuit.

So what are your suggestions? Last owner didnt winterize the carbs, are they the problem? How can the power stop, then come on at full force later?

Winterise carbs........ another myth that has appeared over recent years.  Providing the bike is correctly maintained (very important that bit) you need to do nothing to anything to store it over winter other than garage it and keep the battery charged.  If you were taking it off the road for say a year or 2 then it would be wise to take precautions.  The other myth UK/Euro fuel goes off and blocks you pilot jets, it doesn't.  What does is suspended debris in the fuel,  The main one being rust, how does the rust get there water in the fuel from cheap/poor traders who allow there fuel to get too low before refilling their tanks.  Others are storing the bike with an empty tank over winter, dents in the tank these can damage the coating on the inside and rust then forms, filling up from a fuel can that's got crap in it.

I've recently (3 weeks) took my XJR1300 out of the garage.  It's been in there since Mid Oct 17 with half tank of fuel connected to a Optimate charger nothing else.  I primed the crabs (very important that bit) by turning the fuel cock to prime, put the choke half on (same system as Fazer) hit the starter and it started, got on it and rode it.  The bike rides perfectly the fuel has been in the tank for 6 months, when I got home I topped the tank up with fuel I've had stored in 20lt metal fuel can (commonly known as Jerry cans)  that fuel is about 8-9 months old, I've used the almost every day since, and I've topped up with garage fuel there is/was no difference. 

The same applies to my other bikes all start, and ride as they should all their fuel is at least 5 months old, fuel doesn't go off certainly not over winter.  Some years ago I took my Fazer off the road for 3 years, it was just left in the garage connected to an Optimate, nothing was done to it before or during other than the odd start up perhaps once a year.  It started first time every time and rode perfectly after the 3 years, the fuel was 3 years old!

Based on your other posts (cam chain noise) this bike clearly hasn't been cared for it's possible candidate for a bike that's been clocked i.e. it's got far more mileage on it than it's stating.  Looking at the pictures you posted on U tube I'd say it's looking very ratty for a 40km (25k) bike it's certainly not been looked after outwardly.  As I stated in my other post, take it somewhere that's recommended by other bikers, see what they say.

Good luck keep us posted.