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Discussion Starter · #1 ·
I'm doing my first valve adjustment on my 1973 CB450. I have read a lot of posts on this site and a lot of great guidance has been given. I'm having an issue finding the correct stroke to set the valves on the left side. Is it safe to assume that if I am seeing the notch in the cam shaft, (see picture) and the index pointer is aligned with the LT mark on the alternator rotes that I'm where I need to be to adjust the left intake and exhaust valves??

Once the left side is complete, then turn the alternator rotor 180 degrees counter clockwise to the T mark and adjust the right side. I just want to make sure I'm on the right track - Thanks!

IMG_2416.jpg
 

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Don't try to use the cam timing marks as a guide for setting the valves. Use the understanding of the 4 cycle principle - intake, compression, power, exhaust. The valves are adjusted when the engine is at TDC on compression stroke and both valves are closed - easily achieved by rotating the crankshaft (in the direction of rotation, of course, as shown by the arrow on the alternator rotor), watching the intake valve open on the cylinder to be adjusted, then as the intake valve is closing, stopping rotation at LT (or T) on that cylinder (but before the exhaust valve begins to open). And yes, the right cylinder should follow 180° after the left - but watch the valves to be sure
 

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You can get a feel for proper timing by examining the overlap at TDC that ends exhaust and begins intake stroke:
 

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Discussion Starter · #4 ·
Don't try to use the cam timing marks as a guide for setting the valves. Use the understanding of the 4 cycle principle - intake, compression, power, exhaust. The valves are adjusted when the engine is at TDC on compression stroke and both valves are closed - easily achieved by rotating the crankshaft (in the direction of rotation, of course, as shown by the arrow on the alternator rotor), watching the intake valve open on the cylinder to be adjusted, then as the intake valve is closing, stopping rotation at LT (or T) on that cylinder (but before the exhaust valve begins to open). And yes, the right cylinder should follow 180° after the left - but watch the valves to be sure
Makes sense and what is throwing me off is the fact that when I find the compression stroke based on the intake valve opening and then closing and before the exhaust valve opens at LT, the gap on the left exhaust has a lot of slop that does not go away by rotating the set screw on the adjuster. I have adjusted the other 3 valve without issue to .002 but the left exhaust has me scratching my head. Since I do not know the history on the engine, i hope someone has some insight in this area. Thanks
 

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Make sure that the adjusters are at the correct position; should be visible on this drawing:
valve_adjust.jpg
The gap can come close with the adjusters rotated too far out of the indicated range, but the contact of the follower will be wrong, any may not achieve the proper gap.
 

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Most likely is a worn tappet (or cam lobe).....That is the last part of the engine to receive oiling......
 

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Discussion Starter · #7 ·
Make sure that the adjusters are at the correct position; should be visible on this drawing:
View attachment 284308
The gap can come close with the adjusters rotated too far out of the indicated range, but the contact of the follower will be wrong, any may not achieve the proper gap.
Hey Rick, yes, I have them in the range but I do not understand the second part of your message. Please explain. Thanks
 

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Maybe not for an experienced 450 mechanic, but generally yes.... Too much to type, but phone and I'll explain......
 

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Hey Rick, yes, I have them in the range but I do not understand the second part of your message. Please explain. Thanks
The drawing shows the acceptable range for the adjusters, but they will turn a complete 360; while in the other half of the circle, the follower will also get near the cam, but is extended to make contact in a different part of the follower. Some will reach the spec gap, but the geometry is all wrong for proper lift and duration.
 

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Discussion Starter · #11 ·
Thanks everyone. Yes it was a very warn tappet. Special thanks to 66Sprint for taking the time to talk me thru the repair.
 
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