CB450-Motor-rebuild

[dan_bleichman]

On paper this motor was suppose to to make big power and came with the following goodies:
Valve spring conversion
Dual spark plug heads
Aggressive Megacycle 120x7 cams
Somewhat higher than stock compression (well, there is a high dome on the pistons but also large valve pockets).
But at Mosport 2012 on the back straight I wasn't able to keep up with the stock CB450th.
A leak down test revealed significant leak through the valves on the right cylinder and 90%! leak on the left side.
So the head needs some work. The cylinders pistons look OK though, no sign what so ever of hot combustion gas passing past the top ring

Tapets.JPG

Pistons-good-shape.JPG

[Peter Balfour]

Don't make that thing too fast Dan, my poor old BSA won't be able to keep up!

[dan_bleichman]

For now only fixing what's broken but it is amazing how much performance stuff for this motors is available.
From the information I gathered so far, by spending $3K it is possible to bring this motors to over 60HP at the rear and still have half decent reliability and you don't have to go to the extend of designing and custom machining your own cams and pistons as the CB550 guys have to do.
On the other hand the CB450 just as all Brit bikes of the period do have some fundamental design flows (insufficient oil pump capacity and weak valve train).
The Honda fours don't suffer from any of this.

#525

[Ray Roberts #115]

You will take the top end out of that every time with the mega cycle cams, I used the Norris cam profile and never touched the top end again.
Ray.