Loss of power at full throttle

[Carl]

Bike is a new (to me) 2005 1150 GSA.

After I picked the bike up noticed a loss of power when throttle snapped open fully, didn't worry too much about it at the time as I knew that it was overdue its 12k service, it also had a cracked airbox.

Spent the weekend fitting a new airbox and service replacing engine, gearbox and FD oils. All 4 spark plugs, fuel filter, oil filter and air filter. Was all excited about getting back on the bike to ride instead of working on it, but the damn problem is still there.

It starts first touch and idles fine, but got out on the road into the first NSL cracked open the throttle and it splutters and farts running on just one cylinder (I cant work out which while moving) revs drop and flutter around 500rpm but as soon as the throttle is closed the other cylinder starts firing again and normal operation resumes.

Was able to recreate the fault while out by just pulling in the clutch and snapping the throttle open full, not so scary as losing all power when accelerating hard . Also had the bike cut out a couple of times when coming to a standstill.

Any ideas? Already had coil packs suggested, but why would they only give up at full throttle and work again when throttle closed?

Not done a TB sync and valve adj as was I was going to get these done at BMW along with brake/servo bleed.

Sorry for the long winded post

 

[ELIMINATOR]

http://www.ukgser.com/forums/showthread.php?t=91406&highlight=coilpack

Could be a coilpack, read this. simple to check & costs nowt to do so

 

[RickG]

Had a blocked fuel filter that caused those symtoms, but only on the road when the fuel demand was v. high - bike just cut dead when the throttle was whacked open only to cut back in with a bang when it was shut. Was worse when tank nearly empty.

 

[Carl]

Had a blocked fuel filter that caused those symtoms, but only on the road when the fuel demand was v. high - bike just cut dead when the throttle was whacked open only to cut back in with a bang when it was shut. Was worse when tank nearly empty.

Fuel filter already replaced... Fuel starvation was my first thought. Managed to get hold of a pair of primary coils today, will see what happens

 

[Steptoe]

Managed to get hold of a pair of primary coils today, will see what happens

You don't need another set to find a faulty cap.

Just pull the lower spark ( secondary spark) cap off and see if it idles on the main plugs.
If it's rough, reconnect ONE lower at a time, and see which side connected it runs better.

 

[iletts]

Any ideas? Already had coil packs suggested, but why would they only give up at full throttle and work again when throttle closed?

The spark has to overcome higher pressures and temeratures as revs/power increase, so an iffy spark will give up.

 

[Carl]

Update

Coils....

Borrowed a set to test, and the problem went away. So got 2 new ones today "£110 please sir"
Now got the good old one as a spare.

Engine now running cooler and only showing 4 bars even after a caning.

Thanks all for the advice.