You should take off the R/H side cover and check the Valve Lifters
On the early NE-5 Taiwan used the lifters that were for the WC-1
Taiwan was always trying to save a $ with their stinking thinking
Apparently Taiwan softened the WC-1 lifters so they wouldn't damage the NE-5 cam,
What happens is the bottom of the lifter that comes in contact with the cam lobe starts to mushroom and metal fragments can break off and damage your engine
Whizzer USA offered hardened lifters (under warranty) to those who got the soft lifters and later offered a wide bottom lifter that makes much better contact to the NE-5 cam lobes. But ya had to buy those, The 06 and later models had wide bottom lifters.
Wide Bottom lifters are commonly called "Mushroom Lifters" not to be confused with a lifter that is mushrooming from wear
Having a soft lifter the valve lash has to be constantly adjusted, also the bottom of the lifters mushroom and metal fragments can break off and damage your engine .
I don't know where to find any (Mushroom Lifters) wide bottom lifters anymore
But Whizzer Paul will have the regular hardened lifters for the NE-5.
My 2005 NE-5 came with the soft lifters. I was having to adjust my valve lash alot when I discovered the lifters bottoms were mushrooming Lucky I caught mine in time before it caused any damage.
Whizzer USA gave me the hardened lifters under my warranty, but I later bought 2 sets of wide bottom lifters.
I still run the same set of "Mushroom Lifters" today
Many people have had this soft lifter issue with their 2005 NE-5, So your gonna need to check your lifters
I'm sure if some of my facts are off Ray will correct me
Ray is always teasing me by showing pics of hard to find parts
