Quote:
Originally Posted by bigdano711
Heavy lifter. I know that feeling. When I bought my 2002 Dodge Dakota, suddenly everyone was hitting me up to help them move. Did you play hoops? Football? Soccer goalie? lol My game is hoops, all the way. This Hawk is gonna get me to the rec center, eventually.
I put 100 miles on the bike and decided I better check my valve lash. They were tight, zero lash. I just got done setting the lash and took her for a spin, she feels good.
When they're tight like that, it means the valves are not closing all the way?
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I played football, though not particularly well. I mainly just did weight training and was in ROTC, so I had to meet certain physical standards.
When the valves have no lash the risk comes when the engine gets hot, particularly the valves, which are the hottest individual parts of the engine during operation. They can only shed heat as long as they are in contact with the head, and that contact is the narrow band the seat and valve face contact area, and the extremely minimal contact with the stem and guide.
As they get hot, they expand, and that little gap is there to provided room for the valve to expand so that they don't get pushed ever so slightly open. Even a fraction of a millimeter of a gap at the valve seat causes a loss of compression and greatly reduces the valves ability to shed heat, which then accelerates the problem.
The potential damage and other issues of this were covered already by others, so I won't bother going into that.
One less talked about detail with the CG engine design, and why it can operate with very small valve lash specs when compared to other small singles is actually down to the aluminum pushrods. The cam being located in the lower case half, the cam followers being located in the cylinder, and the valves themselves at the top of the head with all of the engine being made of aluminum means that as the engine also expands and grows from heat the followers move away from the cam and the valves move away from the followers. The pushrods, being the same metal as the engine, expand at the same rate as the engine, so most of the lash put into the valves is to compensate for the expansion of the cylinder that pushes the rockers away from the followers. As the valves get hot they actually help take up some of that slack when they grow themselves. That is why the CG engine runs fine with so little valve lash compared to other engines.
When I played around with the chromoly steel puhrods I discovered that even when set with zero lash, the cylinder expansion was so much greater than the pushrods that the valve noise became fairly loud.