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BobbyPaulk(at)comcast.net
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 Posted: Tue Jan 25, 2011 8:41 am Post subject: Carb Jetting |
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Mike
My first carb was running EXTREMELY rich on the standard jetting and nothing I did would lean it out. The soot would build up in the exhaust pipe and the plugs were covered as well. I was cleaning the plugs every 5 or 6 hrs. Jetting, changing float level, and the inlet needle valve did not make any difference. Make sure you are using the newer black floats. I know for a fact that the original white floats could not shut off the fuel flow at 1.7 psi on that carb.
My second carb with the black floats was running extremely lean with the standard jetting. ( Go figure ) When I went into it I discovered it had a 250 main jet in lieu of the standard 255. I have since re jetted to the 255 main and then up to a 260. Also I have upped the needle jet in stages up to a bored out 290 to 295. I have finally got it running some where in the ball park with no adverse change in fuel consumption.
I do not understand how the same size and make carb can give such different performance with the same parts except for the floats.
At cruise settings my front two cylinders are running 150 deg. hotter EGT ( 1340 ) than the rear ( 1190 ~ 1200 ) with the middle two in between. CHT on the front cylinders are relatively cold 250 ~ 260 and rear cylinders right at 300. I had to modify my Ram Air ducts, get rid of the butterfly baffles on top, and make Lycoming type baffles on the bottom of the cylinders to get to this point.
Bobby
113 hrs.
601 XL
[quote][b]
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wb2ssj(at)frontiernet.net
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| Posted: Tue Jan 25, 2011 5:02 pm Post subject: Carb Jetting |
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Bob, I had almost the same problem when trying to rejet my carb. The jets from bing and others are not the actual sizes marked on the jets. Some are larger then marked and some are smaller then marked. Take a good set of drills and check each one. After I found this out I would get the result expected when changing a jet. Tex
[quote] ---
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aerobiz1(at)gmail.com
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| Posted: Wed Jan 26, 2011 12:08 am Post subject: Carb Jetting |
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Hi Tex & Bob,
Your comments could not have come at a better time. I have just
checked the main jet on a Bing fitted to a J230, and despite being
marked as #255, it measured at #250. I have since reamed it to #260
Cheers
Martin
On Wed, Jan 26, 2011 at 10:58 AM, Tex Mantell <wb2ssj(at)frontiernet.net> wrote:
[quote] Bob, I had almost the same problem when trying to rejet my carb. The jets
from bing and others are not the actual sizes marked on the jets. Some are
larger then marked and some are smaller then marked. Take a good set of
drills and check each one. After I found this out I would get the result
expected when changing a jet. Tex
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