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2danglico
Joined: 08 Sep 2008
Posts: 17
Location: Seneca SC
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 Posted: Mon Sep 08, 2008 11:27 am Post subject: 447 tuning tips |
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I recently bought a used Kolb Firestar with a freshly rebuilt (4Hrs) Rotax 447 single carb. I'm writing in hopes of getting some advise on getting it tuned up. I'm a little concerned about the EGT/CHT temps I'm getting while operating at speed. I'm getting a lot of surging and stumbling. It's difficult to find a happy cruise RPM. Anything below 5000 RPM and it will slowly load up and begin to lose RPM and run rough. When I try to nudge the throttle up a small amount, I get a surge that puts me up to 5500 RPM. My EGT is only reading 850-900 even on my full power climb outs, and my CHT is reading 300-325. I assumed this was indicating a over rich condition but when I checked the plugs I found the healthy looking rust/brown color I've seen in the books. I'm thinking that I may benefit from dropping the needle down(or up?) one notch to lean it out and see if I can bring my EGT and CHT in line. Does anyone have any feedback or opinions? Any help I can get will be appreciated. -John
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Ralph B
Joined: 14 Apr 2007
Posts: 367
Location: Mound Minnesota
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| Posted: Mon Sep 08, 2008 11:45 am Post subject: Re: 447 tuning tips |
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| 2danglico wrote: | | I recently bought a used Kolb Firestar with a freshly rebuilt (4Hrs) Rotax 447 single carb. I'm writing in hopes of getting some advise on getting it tuned up. I'm a little concerned about the EGT/CHT temps I'm getting while operating at speed. I'm getting a lot of surging and stumbling. It's difficult to find a happy cruise RPM. Anything below 5000 RPM and it will slowly load up and begin to lose RPM and run rough. When I try to nudge the throttle up a small amount, I get a surge that puts me up to 5500 RPM. My EGT is only reading 850-900 even on my full power climb outs, and my CHT is reading 300-325. I assumed this was indicating a over rich condition but when I checked the plugs I found the healthy looking rust/brown color I've seen in the books. I'm thinking that I may benefit from dropping the needle down(or up?) one notch to lean it out and see if I can bring my EGT and CHT in line. Does anyone have any feedback or opinions? Any help I can get will be appreciated. -John |
John, this sounds like the jet needle is inside the white cup in the carburetor slide. This is easy to check by loosening the screws on top of the carb and pulling out the slide. The needle and clip should be underneath and outside the cup. The needle and clip go in first on the bottom of the slide, then the spring with the cable go down the middle inside the cup. Make sure the cable end is locked into the bottom of the slide before installing the slide into the carb body.
Ralph
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_________________
Ralph B
Kolb Kolbra 912uls
N20386
550 hours |
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