« Last post by ace.cafe on Today at 03:36:39 PM »
No. With NGK sparkplugs, the higher the number, the colder the plug.
The lower the number, the hotter the plug.
Most of us have found the NGK 6 is just about perfect for the sleeved aluminum cylinder that comes on the UCE 500 EFI engines.
The older Iron Barrels which tend to run hotter seem to like the colder #7 plugs better.
Not to nit-pick, but in the interests of clarification, the Iron Barrel 500 actually specifies an 8 heat range plug as standard. The 350 Iron Barrel specifies a 7 heat range.