31-10-12, 01:10 AM
(This post was last modified: 31-10-12, 01:16 AM by His Dudeness.)
I'm not a mechanic but this is my fisher price understanding of valve clearance :lol
The valve clearance is the gap between the valve and the cam lobe. The cam is shaped in such a way that as it rotates it makes contact with the top of the valve which causes it to be pressed down (ie open) at specific times. Obviously there are times when you need the valves open (ie to get fuel in and exhaust gases out) and there's time when you need the valves closed (ie during compression and firing).
The engine operates at a wide range of temperatures and it is made from different materials which expand at different rates so the valve clearance is a tolerance that's in there to ensure that as everything expands the cam lobe only makes contact with the valve at the precise time that its meant to.
If its too tight (ie the clearance is too small) then you're risking that as everything gets up to temperature the cam lobe might be opening the valve too long and you loose a bit of power. Another problem is that the valves cool themselves by making contact with the head and if they are being held open too long then they don't make contact with the head long enough to cool down and you can burn out the valve and that is the biggest danger of tight clearances. The opposite is when they go loose (ie the gap gets too big). That is less of a problem because they're making enough contact with the head to cool so they're not running the risk of burning out. When they go loose they get noisy and you get that tap tap tap sound. When they go tight they don't make any sound. The reason why they go tight is that the valves wear into the head and so the gap gets smaller.
Thus ends the fisher price lesson on valve clearances :lol
Having said all that you've measured your clearance a bit on the tight side. The bikes not going to explode if you leave them for a while but they're only going to get tighter so its up to you whether you want to do them or not.
The valve clearance is the gap between the valve and the cam lobe. The cam is shaped in such a way that as it rotates it makes contact with the top of the valve which causes it to be pressed down (ie open) at specific times. Obviously there are times when you need the valves open (ie to get fuel in and exhaust gases out) and there's time when you need the valves closed (ie during compression and firing).
The engine operates at a wide range of temperatures and it is made from different materials which expand at different rates so the valve clearance is a tolerance that's in there to ensure that as everything expands the cam lobe only makes contact with the valve at the precise time that its meant to.
If its too tight (ie the clearance is too small) then you're risking that as everything gets up to temperature the cam lobe might be opening the valve too long and you loose a bit of power. Another problem is that the valves cool themselves by making contact with the head and if they are being held open too long then they don't make contact with the head long enough to cool down and you can burn out the valve and that is the biggest danger of tight clearances. The opposite is when they go loose (ie the gap gets too big). That is less of a problem because they're making enough contact with the head to cool so they're not running the risk of burning out. When they go loose they get noisy and you get that tap tap tap sound. When they go tight they don't make any sound. The reason why they go tight is that the valves wear into the head and so the gap gets smaller.
Thus ends the fisher price lesson on valve clearances :lol
Having said all that you've measured your clearance a bit on the tight side. The bikes not going to explode if you leave them for a while but they're only going to get tighter so its up to you whether you want to do them or not.