| Diagram | Fig. 2 — Engine: Cylinder, Cylinder Head and Fittings · ref 15 |
| Subsystem | engine top |
| Listed in parts books | 1971–1973 |
Norton Valve Split Collet
Valve split collet that locks the spring retainer onto the valve stem in the cylinder head.
NMT187 is a valve split collet, the small locking piece that holds the valve spring retainer (cap) onto the valve stem up in the cylinder head. Two collet halves seat into a machined groove on the valve stem and lock in place once the spring pressure is released, keeping the whole valve train assembled and under proper spring tension.
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This one shows up in the cylinder head and valve gear sections of the parts books, appearing in catalog listings spanning 1971 to 1973. It's a small part but an important one - if a collet is worn, cracked, or doesn't seat correctly in the stem groove, a valve can drop into the cylinder, which is not a repair you want to be doing on the side of the road.
We don't have more detail on this one beyond its listing in the valve gear figures. If you're rebuilding a head, it's worth checking the collet groove on your valve stems for wear before reusing old collets, and confirm fitment with us before ordering.
We've never carried this one. Tell us what you're after and we'll go looking — you'll get a price and photos before you commit to anything.
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