No way! nothing over 8 psi should be used. 6 is plenty.The engine should hold the 20 psi.
whenfoxforks-ruled said:You do have the exhaust valve tension and the choke/air screw properly adjusted. Have you done plug checks?
AV8R said:No way! nothing over 8 psi should be used. 6 is plenty.
Here is an excellent post for a leak down test and tester that you can make from standard hardware.
http://www.thumpertalk.com/forum/showthread.php?t=506699
For "knocky" sound check that none of your power valve assembly bolts are loose.
Does the sound go away at slightly higher RPM's? If so it could be piston slap on a worn out cylinder. Did you measure the bore when you had it apart?
You can still measure it by taking off the head and using bore guages and a micrometer to see what the cylinder is at and comparing that to your manual.
Did you check the connecting rod wear? I assume you used a new wrist pin and bearing. If not this could be worn out.
If it is the crank main bearings then you will note movement on the stator or on the clutch side when you grab it and try to move it. There should be no perceptable movement.
whenfoxforks-ruled said:Let it idle for a minute and pull the plug. Wet or dry? How many turns do you have on the exhaust valve tensioner? Would an oval bore make the piston knock?
Could mean piston slap. Only way to tell is to take the head off and measure the cylinder. Cylinder to piston clearence only runs around .002" max. More than this and everytime the piston goes up and down it rocks on the wrist pin and "slaps" the cylinder walls with the piston skirts. This could lead to excessive piston wear and piston skirt failure or uneven wear of the bore.The sound goes away as revs go up. what does that mean?
Con rod excessive clearence (at least in the up and down direction) would be heard throughout the rpm range but at different pitches that would be directly related to the rpm of the engine. The side clearence is a different matter. There is a max limit for this also as the side thrust washers wear out.I didnt check con rod wear.
AV8R said:Could mean piston slap. Only way to tell is to take the head off and measure the cylinder. Cylinder to piston clearence only runs around .002" max. More than this and everytime the piston goes up and down it rocks on the wrist pin and "slaps" the cylinder walls with the piston skirts. This could lead to excessive piston wear and piston skirt failure or uneven wear of the bore.
Was this sound present before the top end? If the bore is worn, I would guess that it was. Although with the lower compression of a worn out top end it may not have been so loud or noticable.
I just rebuilt the top end. The piston that I removed was in perfect shape. Except were it kissed the broken power valve. Very little discoloration anywhere on the piston or noticable wear.
Con rod excessive clearence (at least in the up and down direction) would be heard throughout the rpm range but at different pitches that would be directly related to the rpm of the engine. The side clearence is a different matter. There is a max limit for this also as the side thrust washers wear out.
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