FS90R running rough, stalling

J

joea99

Active Member
Worked good last week. Put in new fuel today, fired up quick, but was "missing", puffing a wisp of white smoke. Warmed up a bit and stopped smoking, but would not reach a "smooth" top speed, appeared to be struggling and never reached "normal" top speed. Struggled to cut any grass.

Pulled the plug which appeared "wet and sooty". Put in a new plug, gapped at .020 and it ran better for a few minutes then started stalling out. Restarted a few times and still would not "max out" for speed and struggled to cut.

Pulled the plug and it appeared to have sooted up already, not even 5 minutes of running. But only on one side of the plug. Pictures attached.
 

Attachments

  • new-plug.jpg
    new-plug.jpg
    308.8 KB · Views: 16
  • new-plug1.jpg
    new-plug1.jpg
    272.8 KB · Views: 15
  • old-plug.jpg
    old-plug.jpg
    193.7 KB · Views: 16
  • old-plug1.jpg
    old-plug1.jpg
    142.9 KB · Views: 16
A 7 is a lot lot colder than a 4
So what is happening is the spark pug is not getting hot enough to prevent carbon build up
And the carbon build up provides a conductive path down the side of the insulator so the spark tracks don the nose rather than jumping the gap .
This is of course assuming that the 4 is in fact the correct plug heat ( check your owners manual ) .
Bosh heat grades & NGK grades are pretty well similar and run hot in the low numbers & colder in the higher numbers and a 7 is quite a cold plug .
 
You must log in or register to reply here.
Back
Top