by JimDirt » Fri Apr 29, 2016 10:12 am
Its not weather the rocker is on it or not , its the fact that the timing marks are aligned and there is a gap of some kind from the valve stem(where the shim is) to the rocker arm , the gap is determined by Valve Wear , and correct Timing Alignment , nothing else , the ONLY things that can alter the gap is Valve Wear or Timing Marks
If the marks are aligned and you have no gap then the valve must be wearing and the shim needs to be replaced with a smaller one , and/or the valves need replacing and the seats cut , remember i said "as the valve wears" ?? , the valve face where it meets the valve Seat is what wears , it is the ONLY "wear item" in the valve train (with the exception of the valve seat itself and the Timing Chain) , as it wears the valve face becomes thinner , as it becomes thinner the valve Stem will stick up farther due to the wear of the face , which decreases the gap between the rocker and the shim/valve stem , which is why you have to adjust the valves in the first place
As long as the tower is properly torqued down when checking clearance , then the ONLY movement of parts (due to wear) can be from the Valve Itself ,as the valve wears and the clearance is gone , then the valve sticking up farther pushes the rocker closer to the De-compressor which can not move as it is attached to the cam that can not move , so to simplify , if the valve wears it decreases the gap , the gap is determined by the timing marks being aligned and the proper shim size being on the valve stem and the amount of wear on the valve itself , which determines the size of the shim needed to keep the recommended gap , nothing else can change those settings
The cam is stationary in the tower , it cant change the gaps , the rocker itself is stationary in the tower , it cant change the gap , the only "wear item" is the valve itself ( and the valve seat to some extent) , so the valve is the ONLY item (as long as the timing is correct and ALL marks are aligned when measuring)that can alter the gap , the De-compressor pin is retained within the cam , it can't make the gap tighter
So no matter what , the gap is determined by the shim size , so basically if you have pressure on the rocker to allow it to touch the De-compressor pin , then it would mean the valve is wearing (or your timing marks are not aligned when checking clearance) and will need to have a smaller shim to correct the issue , or you are in need of a valve job , that's all it can be , the stationary parts have no relevance in the gap , only the valves wear does
Did not mean to confuse you with my prior replies , hope that answered your question
2020 CRF450R
2006 CRF450X
Weiser , Idaho