Funky problem on a 99 Busa... help needed..


Hi gang..

I got a bike from a friend that has some issues,, it's a 99 Busa, and it didnt run on all cylinders..

I started checking things out, and he previously changed the stator and crank position sensor..
My first thought was that the new Crank position sensor was from a newer bike (32bit) so I changed it and
put the old one back in, then the bike started running on all cyl's. but... very poorly..ran rich..

I unhooked the vaccum hose from the map sensor (iaps), then it started running better at idle, but badly at higher rpm..
then.... (yes, its a funky bike) I saw that the aps sensor outlet had been blocked..
The iaps sensor is hooked to all 4 throttle bodies..

so, now im a bit at a loss what to do next..
I have 2 busas myself, but both are 2004 models, so i dont think i can (or want) to swap the ecu...
but are the iaps sensors the same between 1999 and 2004..?

any ideas here ? what should I check next?

Compression ok
timing ok
spark plugs ok
fuel pressure ? havent checked

also one thing I noticed, was when the bike was running the lights flickered.. but.. even though the charging is messed up it should run ok? (ran it on a charger = no change)

thanks in advance from Iceland...
I can only tell you my experience bike is a 2001 and my lights flickered as well and my charging system was fried after checking found burnt wiring and changed out stator and rec/reg and I have no flickering now far as the years being different I'm not sure if there is a lot that's different in those years if its the same gen ......

I'm sure someone with more expertise will chime in ...
Have you checked the ignitation coils? injectors? could be one of them is bad. I have the flickering too on my 99, but couldn't be bothered at this time.
Does it run well when cold and sputters when hot?
it pretty much runs crappy both hot and cold...
ignition coils are ok,
I havent checked the injectors..

I can see that it backfires a bit into the throttle bodies when I rev it..