I know that there had been some previous discussion about B&S engines of the same displacement with different power ratings. Being an owner of the 305 cc engine also known as the 120000 series, my curiosity has been piqued. From what I've gathered, the 305 cc displacement is offered in power ratings from 9 to 11 horse power. It's available as the Intek, Intek I/C, Powerbuilt, Intek Snow and Intek Snow Max. Correct me if I missed any. Having some time on my hands, I pulled up a copy of the service manuals for the 9.5 h.p. model (20A414) and the 11 h.p. model (20E414). I compared parts that I though would have an effect on power output. Things like crankshafts, pistons, connecting rods, valves, head gaskets, carburetors (including jets, gaskets and spacers. Other than some variation of crankshafts within the same power groups for both the 9.5 and the 11 h.p. which do not particularly differentiate between power groups, there is no difference in the part numbers. So, if all parts are interchangeable within all three power groups, what is the secret to the difference in power?
Someone had mentioned that B&S plan to use carburetor restrictor plates on future engines. Not sure if that would work. Restrictor plates are used to restrict flow from the carburetor to the combustion chamber. This in turn reduces rpm. If an engine is designed to produce maximum power at 3600 rpm, the restrictor plate would reduce maximum rpm. So, if an eleven h.p. engine makes max. power at 3600 rpm, the 10 h.p. would be reduced by approx. 10% and the 9 h.p. by approx. 20%. That would equate to the 10 h.p. machine achieving max. h.p. at 3200 rpm and the 9 h.p. achieving max. h.p. at 2880 rpm.
Maybe I'm wrong here. If so, I would appreciate any enlightenment that can be provided. Nonetheless, if anyone can explain the difference in power output from the same engine, I'd like to here what you have to say.
This message was modified Dec 9, 2007 by borat
