1973 cb450 – Part 2
So… after taking the engine apart it was apparent that we couldn’t diagnose the cylinder head properly. The cb450 in the 70’s has a really weird cylinder head design. Instead of having valve springs, it has what are called “torsion bars” which hit the valve to open it, and also, hit the valve to shut it. Really weird…
Also, each piston has 3 rings on it… bottom is oil ring, and top 2 are compression rings. So… the middle ring on each piston was “stuck”. Meaning that it didn’t have any free play in it.
So… I took the cylinder head to a specialty engine machine shop here in the N.E. philly, and explained the rings. They told me that a ring should never be stuck like that, and that’s why oil is burning. Also, they told me not to fuck with the cylinder head. So, I took their advice, didn’t fuck with the head. Ordered new OEM pistons and rings.
We re-assembled the engine on a tuesday night. Then put the engine back into the frame on saturday.
After several kicks, it fired right up and runs awesome. No more smoking. Did the timing and points. Rode it around fairmount park for a bit on sunday. It runs awesome!!!
I’m psyched. Successfully did our first real engine work.
Published - Feb 28, 2013
2021 update – click here. Below is deprecated info… Read about rebuild Part 3 Read about rebuild Part 2 Read about rebuild Part 1 Well… the 450 is finished and it runs. Video at bottom. I’ve riden it about 10 miles so far. Haven’t gone over 5K rpm yet, but it feels super responsive and […]