On The Lift :: Robb’s CB590

For all intents and purposes, this bike started its life as a run of the mill Honda CB550.  A stock CB550, while beautiful in its original form, is capable of a stock 50 bhp at 8,500 rpm.  In a day-to-day application these numbers, when combined with stock carburetion and exhaust, amount to a modest performer of a bike suitable for daily commuting and short highway jaunts.  Now, take a look at the cam profile in these photos of Robb’s motor.  If you’re new to the inner workings of reciprocating engines, look hard.  See that cam profile with its long duration, tall lift, and steep flank?  This beefy cam isn’t stock, it’s part of a Stage 2 kit from Action Fours, an old school performance mods company out of California.  When all is said and done, this Stage 2 kit transforms a stock CB550 into a 590cc machine capable of 80bhp, suitable for prolonged fun on the road and occasional track time.

Before the days of electronic rev limiting, companies like Action Fours used thoughtfully designed racing valve springs that effectively float to protect your engine from over-revving, in this case, at 13.5k RPM versus the stock 8.5k RPM.  Heavy duty Japanese-made piston heads and rings were also included in their kits, bulked up to match the stresses associated with Stage 2 type performance mods.  That said, it’s never enough to aimlessly “go big” with everything when modifying your engine.  For example, there’s no sense in running a hot cam without high compression to match.  Every modification that you make to your engine presents a new set of variables that need to be thoughtfully balanced, or “tuned”, to make for a fast and reliable motorcycle.

For those of you that know Robb, one of our lead mechanics, you’re probably not surprised to miss a glamour shot of a period-correct cafe racer in this blog post.  For Robb, it’s just not like that – mechanical perfection is priority one, and then there’s everything else.  Form follows function, or in his words “a bike that runs well looks good.”  For the sake of discussion, this no-frills CB590 will likely be a well running and ridiculously fast drag bike with a short wheelbase…but don’t expect to see a polished tank anytime soon.

3 Comments


  1. Nathaniel Salzman
    Feb 07, 2012

    To put that 80 horsepower into further perspective, my GL1100 made 83 hp when new and probably outweighs Rob’s CB550 by around 250 lbs. My GL is properly fast and powerful. Slice 250 lbs off of it and I can’t even imagine how snappy that machine will be. Mated to the balance and suspension geometry of the CB550, that ought to be an amazing bike to ride.


  2. Simon Turner
    Dec 14, 2012

    This looks awesome! I had a few questions on this mod. Any info you can give on where to obtain the cam and such? What are all the parts required to do this properly (Cam/chain/pistons/machine work)? Also, is this option similar to dropping in a 650 cam and chain? Thanks!


    • Nathaniel Salzman
      Dec 14, 2012

      Simon, the easiest thing to do would be to just give us a call at the shop. Robb can answer questions about cams, etc. much better than I can.

Leave a Reply

Contact Us

BlueCat Motors
460 N. Prior
St. Paul, MN 55104
(651) 645-1172‎
info@BlueCatMotors.com

Restoration Services

BlueCat Motors Restoration Services

We believe there's nothing sweeter than an old machine running as good as, if not better, than when it rolled off the factory line. A close second is when that machine looks as good as it runs. That's why we offer comprehensive vintage motorcycle restoration services. Whether it's a concourse bike, a resto-mod custom, or even your own take on the perennial Cafe Racer, give us a call at (651) 645-1172 and we'll get the wheels rolling.

buy cipro no prescription buy tadalafil generic online