ST100 FUEL PUMP

[RCMCY]

Have been having trouble with ST1100,s running rough and missing on front right hand cylinder (it must be the last carb to get fuel) one had been giving trouble for ages and changed carbs ignition unit etc but after doing the pump runs perfect, I have done half a dozen bikes all fixed the rough running.
The fix, you can put an aftermarket pump as has been posted before, but I have found the existing pump can be repaired. (the good part is it costs nothing)
After removing the original pump I have not been able to get the end off whith out slitting the cover but then with the armature out clean the comutator with some fine sand paper and reasemble fixes the problem.
There dosen,t appear to be anything wrong the armature looks okay but obviously must have a film over it.
Don,t know how long it will last but my ST has now covered 10,000klms since and is still going perfect.
There is a discription on the American ST site on how to do it (as always found after I fixed it.)
Cheers
Ron Hewitt

[Pezzz]

 
Thanks for the tip.

[johnnyYTED]

 
  I'm hoping I don't need this info for a long time  but great info to know, thanx Ron.
 

[Yorkie]

From my experience with armatures this will only be a temporary fix, the commutator needs to be undercut, that is putting a sharp point on an old hacksaw blade and cutting away the white insulators between the copper segments. The problem is caused by the soft copper wearing leaving the insulator sitting proud and preventing proper contact with the brushes.