As I progress through the refurbishment of Project 37, a 1993 VFR750, one of the items at the top of the checklist is a valve clearance check and adjustment. Beginning in 1990, the VFR's valve adjustment is accomplished via the "shim-under-bucket" arrangement whereby replaceable shims of varying thickness are exchanged to achieve the recommended clearance, also referred to as "lash." This design provides a very positive mechanical setting which is able to survive high-RPM operations without the threat of "spitting" out a shim as can happen with a "shim-over-bucket" arrangement. Honda must have thought that our high-performance, high-revving engines deserved this design, though interestingly, the earlier generation VF/VFRs seemed to have gotten by with the simpler screw & locknut approach. In fairness, those earlier systems required old-fashioned rocker arms for valve actuation which are more complex and heavier, adding reciprocating mass and, likely, high RPM flexing. But, that earlier design makes our life easier when adjustment time comes about.
In any case, owners of 1990+ machines will need to set aside more garage time (or expect to pay a shop more) in the event their valves are in need of clearance adjustments, which likely leads to this task being put off or outright ignored as part of a normal maintenance regimen. Of course, that's understandable when an owner realizes that, in order to replace a shim, the appropriate camshaft needs to be removed from the cylinder head…and there's four of 'em. So, if you're confident in your wrench-turning abilities, here's a video showing the steps involved in accessing the area for the clearance checks and removing/installing the cams, if necessary.
In this case, all eight valves of the rear cylinders required adjustment along with three of the front intakes and none of the front exhaust. So, three of the four cams required removal.
The second video shows the math exercise required to select the correct replacement shims. I wish I knew how to make math interesting but, alas, I don't.
NOTE: Once I gained access to the valve covers this entire operation took me about 2.5 hours of labor plus the better part of a week waiting for my local dealer to provide the three shims I didn't have on hand. There should be no additional parts needed beyond the required shims, though this is a perfect opportunity to replace the spark plugs. As noted in the shims video, the Haynes service manual is the more thorough guide for this operation.
In any case, owners of 1990+ machines will need to set aside more garage time (or expect to pay a shop more) in the event their valves are in need of clearance adjustments, which likely leads to this task being put off or outright ignored as part of a normal maintenance regimen. Of course, that's understandable when an owner realizes that, in order to replace a shim, the appropriate camshaft needs to be removed from the cylinder head…and there's four of 'em. So, if you're confident in your wrench-turning abilities, here's a video showing the steps involved in accessing the area for the clearance checks and removing/installing the cams, if necessary.
In this case, all eight valves of the rear cylinders required adjustment along with three of the front intakes and none of the front exhaust. So, three of the four cams required removal.
The second video shows the math exercise required to select the correct replacement shims. I wish I knew how to make math interesting but, alas, I don't.
NOTE: Once I gained access to the valve covers this entire operation took me about 2.5 hours of labor plus the better part of a week waiting for my local dealer to provide the three shims I didn't have on hand. There should be no additional parts needed beyond the required shims, though this is a perfect opportunity to replace the spark plugs. As noted in the shims video, the Haynes service manual is the more thorough guide for this operation.
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