Question on strange cb500 exhaust

carnivorous chicken

carnivorous chicken

Over 1,000 Posts
In PHX taking care of stuff and went by Stan's place. Cool old dude, he raced BSAs in the 1950s, still has one of his race bikes, and a 1939 Indian. He's also got a yard full of 40 bikes or so, lots of cbs, and parts. Saw a cb500 today with a 4-1 system where the head pipes wrapped over the oil filter on to one side similar to 400f or 550f stock pipes, but they collect into one about 8-10 inches from where they mount, in front of and above the oil filter, as opposed to much further back like most systems. Any exhaust gurus know these pipes, or why they might have benefits or be worse for performance, or not matter?
 
Sounds like the Action Fours header set up. They ran really short headpipes before the collector. They were designed to be a top end pipe along with their 590 kit and cam. We roadraced one back in the late 70's and it worked pretty good. At a track like Road America where you could get a long straightaway run, it could just stick with a stock GS1000 on top end.
 
VY - I can try to make it back there, but after googling CB550 action four exhaust, the images show what I saw.(thanks ex119x). Think its worth anything? It's in a yard here and I could likely get it for $100 or so. It's in decent shape (in AZ, so no rust, but it was painted/coated and not too pretty in that regard).
 
Action Fours was pretty race oriented, so their stuff was never chromed or fantastically finished even when new. It was functional not fashionable. It has some value as a period performance part. Action Fours had a whole catalog full of parts, so it might be interesting to know what else that bike has besides the pipe.

If you could get it cheap, I would.
 
Good to know. I can't make it back there on this trip, but will be back in 6 months or so, and will make an offer on the whole engine to see what it's got inside. Thanks a lot for the info ex119x!
 
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