Sunday, January 31, 2010

Blown Cub slowly in the works.

Decided to go with a Chevrolet smog pump. This has been tried successfully on go karts and a 50cc Honda road racer I found. On the Honda 50 it was under driven quite a bit so on my 200 (stock displacement this year) I'm going to try 25% over and see what happens. I will have other blower pulleys to overdrive it more if needed. If it will show just a few pounds of boost I think that would make a noticeable difference. Stay tuned.....................


  1. I too looked at using the smog pump for a blower on my 400 cc diesel bike. However, they only flow roughly 5-7 CFM at stock RPM (depending on the manufacturer) requiring them to be greatly overdriven to be of any benefit. Even then, efficiency drops exponentially with RPM due to the limitations of the vane arrangement. As you noted, they are however good for a few pounds of boost. Yet, a 200 cc engine at 3500 RPM is needing to flow at least 13 CFM requiring the smop pump to be driven at twice the RPM for which it was designed, putting it in the range where one would want some protection between it and vital organs/parts. The absence of a protective shield could result in forms of "Planned Parenthood" never envisioned.
    Having said all that, I do love the look of your bike and the attached pump. If for no other reason, keep it for aesthetics.
    I secured a NOS little roots blower that would be sized about right for your application, but sadly is still a bit too small for my 400 cc lump. I'm now going with a 2 stage centrifugal blower that is sized almost perfectly.
    Please don't take this as a critique of your efforts. I love what you're doing and hope that you're ultimatley successfully. And do keep us posted.

  2. The zip tie could indeed provide one form of "Planned Parenthood". A radically over-driven smog pump shedding parts into the lower anatomy was what I had in mind, qualifying one for consideration of the Darwin Award accompanied by the ability to reach notes in the tenor range heretofore unattainable. That's assuming you lived. The very thought causes an involuntary and unconscious need to cross my legs.