This is a findings report on a set of new replacement exhaust valves for the mid size bikes and fellow rebuilders.
Short version - Shin Nippon Valves are a downgrade from OEM
Long version - Though an affordable alternative to NOS Oe parts (and KMPI products). The nippon valves are not a great choice for servicing the valve trains. Here's why.
The valve lacks any sort of performance coating or visible post processing.
The grind on the back of the valve dome does not achieve the same standard as oem.
The grind along the stem of the valve is rough in its surface quality.
When measured side by side with a used oem valve of favorable condition. The nippon valve stem is ~.0015" under sized to the used oem.
Comparing fitments with a new, uninstalled dynoman bronze valve guide - the sliding fitmet of the nippon valve issimply poor. Side play inside of the guide feels on the edge of unusable.
My pain is your gain, lesson learned.
