OK, this is my take on the shim bucket verses the tappet adjuster valve clearance adjusting methods.
I am not saying this is 100% true with the two engines you are comparing, but this does hold true with most all bikes that I have experienced since 1988 on the shim valve motors.
Shim valve motors are a little more sophisticated and need a little tooling to make valve clearance adjustments, also if you do not have a good selection of shims on hand you will need to make a trip or two the M/C shop to either exchange one for another (yes there are some shops that will do this for a small fee) or just buy the ones you need.
I have found that almost all shim valve motors do not need to be re-shimmed on a regular basis (most street models will go 20K to 35K miles with out needing to be re-shimmed), but it is wise to check clearance on the recommended maintenance schedule.
For the most part the only time they need to be adjusted is when some one tightens a loose valve clearance. Most of the time a loose valve clearance is do to a carbon build up on a valve face or seat. Most shim valve motors are high revving and lugging them around or using low octane or low grade fuels will cause a valve to carbon up. It is my personal belief that all M/C engines be run hard at high RPM prior to checking valve clearance.
If a shim valve motor has a tight valve clearance (this could be a little normal for higher mileage engines). This usually indicates valve seat wear or a valve face is cupping. In this case you will want to keep an eye on that valve and if it continues to tighten, it might indicate that the valve should be replaced and valve seat re-cut.
Valve tappet adjuster motors are very straight forward and easy to adjust once you get access to them (some time this can be hard do to frame, body parts, etc.). It does take a little experience to master but is no big problem.
I have found that most all adjustable tappet motors need to be adjusted on a very regular basis. There are a lot of wear points that are always changing, such as rocker arm pivots, the tappet adjusters them selves, top of the valve stems and the rocker arm followers.
So, it is my opinion that the shim valve motor is a better design (provided the engine manufacture did their job) and is less maintenance than the tappet adjuster motor.
Thank you,
Ron
Please note! There are exceptions to ever rule and the above is my general experience with both type of valve systems.
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