9.9 spark plug problem

[tony6813]

pulled the plugs and found very different conditions on plugs. gaps are the same but dont look like proper combustion. any ideas on where to start. carb has been rebuilt and compression is also not the same in the cylinders. 90psi and 140psi. do i have a rebuild project this winter? This is a 2000 4 stroke 9.9.

 

[racerone]

Check valve clearance before anything else.

 

[tony6813]

any special tools needed besides a feeler gauge and what about adjusting them? never took apart top end before,any advise in advance of what to look for? thanks

 

[Vic.S]

Is the black looking plug oily ? Does it come from the cylinder with the low compression ? If so theres a good chance of a broken piston ring or worse.

Checking valve clearances first a good suggestion though.

Get a workshop manual before you start.

Looks as though checking and adjusting valve clearance will simple enough.

 

[racerone]

I understand that there is a " history " of rockers wearing prematurely.---------Have 3 of these motors and one needs rockers repaired as new ones are not available at this time.