Honda made several changes/upgrades when the RC26 F2 (700cc) replaced the RC24/26 F models (700 & 750cc) in late 1986. One of these was a change to a fully transistorized ignition system requiring several different components, including the pulse generators located inside the clutch cover. Another is the addition of "rocker arm spring"/"rocker arm guide" components in the head assembly surrounding the spark plug holes (1987 only). Reference the photos below.
Both of these items presented a roadblock to me yesterday as I removed and prepped the valve & engine covers for powdercoat on Project 41, a 1987 F2. I wanted to temporarily install spare covers while the originals were off for paint, but my spares happened to be '86 F model items. The alternator cover is interchangeable but the valve covers on the F have cast-in "towers" which interfere with the F2 rocker arm guide assemblies while the F clutch cover pulse generator bump-outs are too small so won't fit over the F2 pulse generators. I was aware of the clutch cover interchangeability issue but had never encountered the valve cover problem, which was a running change for the 1987 model year.
The photos below show the pulse generator bump-out castings on the clutch cover, and how the "towers" inside the F valve covers are "missing" from the later F2 castings, preventing the earlier valve covers from fitting the later cylinder head. This also required a change to the valve cover gaskets, which have individual round gaskets for the spark plug holes, instead of the earlier "bridged" gasket design — subtle, but necessary. As for the clutch covers, you can visually determine the difference in the two styles of clutch covers as the later F2 pulse generator cover's forward bump-out measures 1/4-inch (6mm) longer than the earlier F casting.
The photos below show the pulse generator bump-out castings on the clutch cover, and how the "towers" inside the F valve covers are "missing" from the later F2 castings, preventing the earlier valve covers from fitting the later cylinder head. This also required a change to the valve cover gaskets, which have individual round gaskets for the spark plug holes, instead of the earlier "bridged" gasket design — subtle, but necessary. As for the clutch covers, you can visually determine the difference in the two styles of clutch covers as the later F2 pulse generator cover's forward bump-out measures 1/4-inch (6mm) longer than the earlier F casting.
The take-away here is a reminder that changing out your Gen-2 engine covers for different items requires some investigation beforehand. While the later F2 clutch and valve covers should fit both F and F2 engines, the F covers will not fit the F2 engines. Clear as mud? Again, the alternator covers are interchangeable.
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