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Post by stuckchuck on Mar 3, 2015 22:39:52 GMT -5
Yeah it lines up right after the compression stroke but not during it so why confuse people? It's TDC. The piston is at the top of it's stroke. daath may already know all about it anyway.. my post wasnt for daath any way? it was for the original poster to see if he was doing it right? |
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Post by Fox on Mar 3, 2015 23:17:20 GMT -5
So you're saying a compression stroke and TDC are the same thing then. Thanks for enlightening us. I stand corrected.
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Post by 90GTVert on Mar 4, 2015 11:54:25 GMT -5
The issue is that if you try to adjust valves at the wrong TDC the valves may be partially open because there is a period of overlap on the TDC between the exhaust and intake strokes. There should be no valves open when at TDC between compression and power strokes. Exhaust is pushed out of the cylinder on the exhaust stroke with the piston moving up the bore and the valve is still open to some degree as the intake valve begins to open and the piston changes direction and restart the process.
If your cam and flywheel marks are all lined up you've got the right TDC so you don't really have to think about all of this.
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Post by Fox on Mar 4, 2015 12:45:14 GMT -5
The way I see it is that the cam and the rocker assy. have no brain so they don't know where the piston is nor should they care if they could reason. If the cam is in the proper position regardless of where the piston is then both valves should be closed.
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Post by 90GTVert on Mar 4, 2015 12:56:02 GMT -5
Right, the valves will be closed as long as the cam is lined up with the marks up because both rockers should be on the base circle of the cam at that point. You could install the cam so the marks are up and the valves are closed at totally the wrong time relative to the crank/piston if you wanted. It wouldn't run or run poorly and possibly destroy itself when the piston hit the valves, but the valves would be closed whenever the cam's marks were facing the right way.
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Post by Fox on Mar 4, 2015 13:19:51 GMT -5
Exactly! So if you are doing a valve check/adjust on a scooter that runs but runs kinda crappy then the odds are the cam is properly installed so there really is no need to get into the fan cover and look at T marks or to use your words "think about all this". I think we've beaten this horse to death now.  |
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