Roger Lee Posted April 28, 2015 Report Share Posted April 28, 2015 Not only do the bowls need to be checked, but the carbs need to come off and have every orifice blown out. You may have a piece of hose or float skin in an orifice that moves around or closes off when more fuel or air runs through that orifice. See the picture. You can pop them off and just get this done or spends days or even weeks looking for the issue. Just take the carb throttle arms off with the 11mm nut and the same with the choke. Then take the carb top off. Now the carb can come off without losing any of your adjustments because you have disconnected the cable at their attachments. Little pieces in an orifice can act as a flapper valve. Link to comment Share on other sites More sharing options...
FastEddieB Posted April 28, 2015 Report Share Posted April 28, 2015 Great advice about removing the arms - never occured to me! And after 7 years and 500 hours, rebuilding the carbs is probably a good idea regardless. Roger does them for a reasonable rate, and with a quick turnaround, at least when he did mine last year. Link to comment Share on other sites More sharing options...
Roger Lee Posted April 28, 2015 Report Share Posted April 28, 2015 I rebuild quite a few carbs a year and have a 1 day turnaround. Some of our aircraft are not only getting a lot of engine time, but some accumulate time just sitting. For instance a 2006 CT is now 9 years old. As the carbs age in time and or hours the "O" rings do crack and split at times. Some owners rebuild carbs at the 5 year hose change and some wait. When they start getting up to 7-8 years or 800+ hours whichever comes first is when I think it's not a bad time to get them rebuilt. A good rebuild kit replaces the diaphragm, all "O" rings including the one on the end of the butterfly valve shaft, the 2 butterfly screws that are peened over, the needle valve, the main jet needle and guide, the bowl gasket and choke gasket with its "O" ring, checking for smooth movement of the choke mechanism (corrosion does build up on the edges of the choke mechanism which tends to be more prevalent in humid damp areas of the country, Many "O" rings are hard when I see them and some are cracked and split. The majority of the time float will last to TBO. Rotax has nothing in writing to indicate a rebuild time only a 200 hr. inspection. p.s. Carb rebuild tips: Dental picks go a long way to make "O" ring installation and removal easier. The fixation screw that holds the main jet needle in place down inside the piston is Loctited in place. You need to take a heat gun or small butane torch and heat this really good down inside before you try and remove this screw. Many have found out the hard way that failing to do this causes you to over torque the straight slot screw head. The top head just breaks off. Then you have a mess on your hands trying to get it out. You don't want to go there. Next tip when you put this screw back in place don't put a lot of Loctite on the fine threads or you may have a worse time trying to get it out next time. One tiny tiny drop is all you need. The butterfly valve plate has a punch mark on it many fail to see. IT MUST face outward and be located at the top. The chokes are right and left dependent, don't swap them and they have a punch mark on the choke shaft that faces toward the side that looks like it has a tube coming out the choke body. ALWAYS measure and set the float armature heights while the carbs are off and getting new parts and a new needle valve. They must be held upside down to do this. Link to comment Share on other sites More sharing options...
Steven Posted April 28, 2015 Report Share Posted April 28, 2015 Thanks Roger and FastEddie for the detailed replies. I'll print them out and give them to my mechanic. And before flying the plane to him I'll do a very long engine run-up check including a test of full throttle. Link to comment Share on other sites More sharing options...
Roger Lee Posted April 28, 2015 Report Share Posted April 28, 2015 Hi Steven, Many times an obstruction won't show up on a ground run regardless of throttle amount. Sometimes if the problem is moving around like it can in the bowl then it sits too still on the ground, but in the air at a more continuous full throttle it moves where you don't want it. I have seen this a lot over the years. At a minimum check the float bowls. Link to comment Share on other sites More sharing options...
Polar Posted July 14, 2016 Report Share Posted July 14, 2016 Thank you Fast Eddie B. (And all who contributed) Just fixed my loss of power on T.O. Little piece of rubber in carb bowl... Suspect it flaked off one of the floats. Dave Link to comment Share on other sites More sharing options...
FastEddieB Posted July 14, 2016 Report Share Posted July 14, 2016 Glad to help! Be sure to thank all the other folks who chimed in as well! Link to comment Share on other sites More sharing options...
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