Not firing on all four

[andy from roxeth]

My girlfriends 1500fwd lost power the other day and after swapping everything I could think of for good used parts and going over it with a test lamp I finally got it to start. The problem now is that it needs full throtle to keep running and feels like it only fires on two or three. I can now hear a loud knock from somewhere that I couldn't hear while spinning it over on the starter motor. Any ideas?

[cliftyhanger]

Firing order of ignition leads? 1 3 4 2 anticlockwise. Amazing how easy it is to get it wrong!

[Triumph1300]

Head gasket?

[trackerjack]

1500's and there bretheren have their coils mounted on the suspension turret and sadly this results in the spark jumping all over the place sometimes when its damp! Typical BL which was repeated on the Montego .
I doubt that this is your problem though and would look to a partial blocked SU needle valve.
Oh really it could be several things and using a process of elimination hunt it down.
Good luck.