My CB450 Saga

ericfreeman

Veteran Member
Joined
Jul 12, 2025
Total Posts
230
Total likes
290
Location
Ferndale, WA
A customer recently brought me his 1972 CB450 that was previously at a different shop where they told him one cylinder was dead and there was nothing they could do. He brought the bike to me to see if I could help. Over the past few weeks I reset the valves (all were tight), removed and checked the cam chain tensioner while the valves were all slack, set the points and dynamic timing, replaced faulty spark plug caps and fitted new B8ES plugs. I also cleaned the carbs, which were in pretty good shape. I found a massive vacuum leak on the right carb at the manifold/head joint so pulled both manifolds and replaced the gaskets.

After balancing the carbs using an infrared gun on the header pipes, I went for a road test. Bike ran great until about 4-5,000 RPM when it would start stuttering. Right plug looked good while left was black and sooty. Re-checked everything electrical (about 5 times) and couldn’t find any faults. Pulled the left carb (about 6 times) and finally noticed the Air Idle Jet, that little brass tube pressed into the intake bell at the 6 O’clock position. I didn’t realize it was a jet and yes, it was blocked. Soaked the carb overnight and used a .45mm welding tip cleaner to clear the small passage. Also checked the right carb and it was OK.

Bike now runs fantastic and revs smoothly throughout the range. A great riding bike and I’m envious of the owner.

Moral of the story is to check EVERYTHING and never assume you haven’t missed something. I’ve done lots of carbs but this was a first for me. Glad I found it and I was ready to pull out what little hair I have left!
 
Nice work sorting out the issue. Please allow me to add a couple of illustrations for future readers. I can't get over the beauty of the Keihin CV carburetors — they are an engineering masterpiece.

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This anecdote underscores an important part of vintage motorcycle ownership. It's so much better if you can maintain and repair your own machine.

My impression is that many shops struggle with the cost/benefit ratio and turn away vintage bike jobs to avoid the hassle, especially if it involves some sort of phantom issue. It can be difficult to determine a fair cost when it takes several hours of labor to arrive at a solution that could be implemented in thirty minutes.
 
Good job. I love the fact that one shop said the cylinder was dead and there was nothing to be done. Waaay too many people out there claiming to know how to work on the simplest high performance machines ever built in my lifetime, when they clearly don't know the basics.
 
stl360+450 said:
It's so much better if you can maintain and repair your own machine.
Click to expand...
It's rapidly approaching, if we're not already there, that one has no choice

In Puget Sound at least, all the dealerships are gone or going and the independent shops have headed down the long trail as well. So what's left are modern bike mechanics who know just enough about vintage to get in trouble
 
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