1999 flat spot on cold start up

[black bart]

Busa started playing up after a recent oil and filter change (now done 22,000 miles), feels like a fuelling problem. THe symptoms are:
On cold start up erratic revs up to 2500 revs down to 1500 cough splutter back to 2500. Always was very smooth.
big hesitation or flat spot if you try to rev it at all, grab a handful of throttle and it will almost die.
Once its warm its OK and will tick over and rev quite smoothly.
It is defo down on power inital pick up is a little slower, midrange is almost competly normal so 80 - 110 mph in top gear feels great.
Full throttle in say 5 th does not have the same rush, there is not the same urgency at 9000 to 11000 revs and it feels strained, used to just go into hyperdrive.
First gear acceleration feels like its thrashing at 9000 revs

It has a clean K&n air filter and iridium plugs. Fully synthetic amsoil 10w 40 oil. Drained tank and cleaned out tank filter, removed fuel line and blew out with an air hose, fresh fuel.
Got some problems with the alarm after the battery was disconnected, so have removed the whole system and set it back to standard.
No codes or warnings are being flashed up.
Anyone got any ideas about what it could be

 

[black bart]

UPDATE:
Tonight I went to adjust the tick over, knurled knob on right side of engine.
Turned it the engine cut out, would not start, F1 error, turns out it had blown the fuse to the fuel pump
cover off replaced the fuse.
engine started went to adjust the tick over again and it did the same thing., obviously there is a problem, anyone any idea what it might be. replace the fuel pump?

 

[rusheriv]

What's a "tick over"?

Pinched fuel line?

 

[black bart]

Hm sorry bout that, tick over = idle speed

 

[pgeofm]

Check that the fuel pump plug contacts are clean and in good shape. Could be making contact with one another if corroded or dirt inside plug.

 

[delbert]

many a post on choked / clogged up fuel pumps on here early busas with external pumps suffered

do a search you will find some useful info , good luck

 

[black bart]

Yeah I did a search before I posted, and found a few bits and pieces but nothing that seemed to fit my problem.
Why on earth would the 10 amp fuel pump fuse blow when I try to adjust the idle speed with the engine idling?
Switch the engine off, turn the screw, start it up its all fine.

Anyone got any links to reconditioned or replacement fuel pumps they would recommend?

 

[delbert]

strange one , got to be wiring to pump shorting somewhere , i would pull the pump , strip and clean out screens first / check wiring

 

[moloko]

strange one , got to be wiring to pump shorting somewhere , i would pull the pump , strip and clean out screens first / check wiring

If you're going to do that, do the external filter mod while you're at it. You'll be glad you did.