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Rotax problem

edward7048

Well Known Member
I pulled the sparkplugs at around 20 and 40 hours and found that
the plugs in cyl.# 1,3,and 4 were black with soot and #2 was clean.
The compression was the same on all cyl., carb. are in balance and
engine runs smooth and have used only 91 octane no ethanol fuel.
Has anyone else had this problem?
 
Much discussion of this on the ROTAX-OWNER site. Apparently it is normal and is a result of prolonged idle operations just before checking plugs. I suggest that you visit the ROTAX-OWNERS site for more information. Also see 9/15/14 post on this VAF forum re: "Cylinder #1 spark plugs Rotax 912ULS".
 
Last edited:
Hi Edward,

No problem. Black dry soot can form during idle operations, but goes away during higher rpms. The sooty plugs can be different from time to time and may even disappear from time to time.

Only worry when there is a large mag drop issue and the plug is wet and black.
 
Hi Edward,

No problem. Black dry soot can form during idle operations, but goes away during higher rpms. The sooty plugs can be different from time to time and may even disappear from time to time.

Only worry when you have a larger mag drop and the plug is wet and black.
 
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