From: John De Armond Newsgroups: rec.outdoors.rv-travel Subject: Re: Champion Generator review Date: Sun, 05 Nov 2006 05:06:35 -0500 Message-ID: <65glk2lo6drhhv57uj62tf4do66q1li2ji@4ax.com> On Thu, 02 Nov 2006 17:12:13 GMT, "Victor V" <slackamn@aaahawk.com> wrote: > ><boondocky@no.spam> wrote in message >news:3d6kk291i2kt2qr6eqfhf143lej65ssep3@4ax.com... >> "Victor V" <slackamn@aaahawk.com> wrote: >> >> I'm not sure what the "coming from you" part means, but I'm taking it >> to mean "coming from a guy who has been dry-camping for going on 4 >> years straight in high-altitude cold-weather conditions". <g> >> > >Yeah, that and I find that smart-ass guy to be too over the top. Never >listen to him for anything. Good idea. Won't go wrong there. >All good stuff. You reckon my gen will run OK at altitude? Say 9K? At 9K? Probably not. From the US Standard Atmosphere chart, http://www.sworld.com.au/steven/space/atmosphere/ at 9K feet, the air is only about 77% as dense as at sea level. Thus, everything else being equal (it isn't), the power loss from altitude alone would be about 23%. This assumes the mixture is correct at 9K which it won't be. You should expect additional power loss from non-optimal mixture strength. Since small engines are now set to run very lean to meet EPA restrictions, the degradation might not be as bad as in previous years. Still, a high altitude kit (different jetting) would be appropriate. Honda sells such kits for their GC series engines which most of the ChiCom clones appear to be cloned from. If a high altitude kit isn't available from the generator's importer then perhaps you could figure out exactly which Honda engine they cloned and order an altitude kit from Honda. Does the manual for the generator mention any sort of altitude kit? Considering the range of elevations in China, I'd not be surprised to learn that they'd addressed that matter already. If you can't buy a kit then you can make one. All you really need is a different size main jet since the generator won't be idling much at all. If they cloned the Honda carb then the main jet should be a brass screw-in element. I used to make jets for "non-adjustable" carburetors fairly frequently in days past before EFI displaced carbs on almost everything. A spare stock jet makes things very easy, as it can be modified without risk to the carb if you screw up. The drill (pun intended :-) is to close the jet's hole and then drill/ream it to the desired size. For brass jets I solder the hole shut. For jets drilled into the carb's pot metal body, epoxy works well. I use a combination of orifice drills and watchmaker's hand reamers, both of which should be available from McMaster-Carr, MSC, etc. I got mine decades ago so I'm not sure of modern sources. Orifice drills are designed to drill the orifices of gas and oil burners when changing the output, converting from gas to propane, etc. Mine start out at 0.015 and go up in 0.005" increments. Watchmaker's hand reamers are tiny reamers used to ream the tapered hole in a watch hand to fit on the shafts. My set starts out at probably less than 0.015" and goes up in several pieces to perhaps 0.100". For watch making, one simply reams the hand opening until the hand fits tightly on the shaft. For carb tuning, one simply reams the jet until the correct mixture is achieved. I always record in my tuning notebook which reamer and how far it protrudes from the jet so that I can reproduce the jet when needed. A low performance generator engine should be very tolerant of mixture so it should be easy to get close enough with one or two tries. If the length of the metering channel is kept the same as stock (easy to do with solder) and the entrance and exit tapers are maintained then the altitude compensation will involve shrinking the AREA of the jet's hole roughly in proportion to the reduction in air density. At 9K feet, for instance, you'd reduce the AREA of the jet's opening by about 23%. Once you get the mixture close you can tune it in by varying the float level, the limits on that being overflow on the high end and uncovering the idle jet on the low. This sounds like a lot more work than it is. Once you have the drills and/or reamers in hand, making the change is perhaps a 15 minute job. Drop the float bowl, remove the jet, solder shut, drill and deburr the hole, re-install and that's it. John |