procharger Posted July 2, 2015 Report Share Posted July 2, 2015 Can I order carb rebuild kit form BMW, or where is best place to purchase? Link to comment Share on other sites More sharing options...
Roger Lee Posted July 2, 2015 Report Share Posted July 2, 2015 You may want to stick with getting them from Bing or one of the Rotax service centers. The main jet and needle may be different. Link to comment Share on other sites More sharing options...
procharger Posted July 2, 2015 Author Report Share Posted July 2, 2015 is there any reason to change main jet Link to comment Share on other sites More sharing options...
Anticept Posted July 2, 2015 Report Share Posted July 2, 2015 Fuel varnish if you have it built up, but just use a carb cleaner and let it soak. Do not change the orifice size though. Aircraft engines run in far harsher conditions than motorcycles short of racing. Link to comment Share on other sites More sharing options...
procharger Posted July 2, 2015 Author Report Share Posted July 2, 2015 What is in kit I see diaphrams gaskets and o rings is that it Link to comment Share on other sites More sharing options...
Anticept Posted July 2, 2015 Report Share Posted July 2, 2015 Different providers have different packaging. Lockwood packages just the o rings and gaskets in the basic kits, for example. Leading edge's has the diaphragm (unnecessary, IMO). Here's what I think: O-rings: In my opinion, replacing the o-rings, if you inspect often enough such as in a flight school plane, is unnecessary if they are in perfect health. I keep a small stock as I always find one or two o-rings that show some surface wear. In the industry it's customary to replace any o-rings you find, but I think that's an old "just in case" thing that mechanics did because the rings are usually old, difficult to get to, or undergo a lot of stress, like in hydraulics. Unless you are Gunthering the carbs together or inspect only once every couple years, none of these are a problem, the carbs are quite gentle on o-rings. If you lubricate the gaskets before putting them together, and don't see any damage, I don't worry about the phenolic gasket replacement either. Cork, on the other hand, gets replaced immediately, as it never fits quite right the second time. Diaphragm: if it's still soft and no cracking, replace only at the 5 year. Floats: look em over. If they still float and the surface isn't coming apart, they are fine. Comply with the safety bulletin though!!! Brass parts: soak em in carb cleaner from automotive stores (remove and replace o-rings if you do this!). Takes the varnish right out. Might need to apply some to the carb brass area where the fuel inlet needle with the viton tip rests in. Don't submerge the viton tip at all! If you have varnish on the viton tip piece, polish it off of the corners. Finally, take a piece of stranded electrical wire, size 14 or smaller, and remove a strand of copper. Use it to clean the idle jet hole. Link to comment Share on other sites More sharing options...
Doug G. Posted July 2, 2015 Report Share Posted July 2, 2015 There are two carb overhaul kits I have seen. One is mainly gaskets and o-rings. The other has a number of other parts. CPS or Leading Edge Airfoil (LEAF) have them. The most difficult thing I can see is peening the screws on the butterfly. Link to comment Share on other sites More sharing options...
Anticept Posted July 2, 2015 Report Share Posted July 2, 2015 Dowel rod for support on the screw head side, take a small metal rod, place on the end of the screw, and give it a rap with a hammer. Just need to give it a little bulge, I've seen a couple where it looks like they put it in a drop forge. Link to comment Share on other sites More sharing options...
Doug G. Posted July 2, 2015 Report Share Posted July 2, 2015 Rotax-owner has a good video on carb overhaul. Link to comment Share on other sites More sharing options...
Roger Lee Posted July 3, 2015 Report Share Posted July 3, 2015 The better kit has "O" rings, two gaskets, main jet, jet needle, needle valve, new butterfly screws and diaphragms. The "O" ring only kit is better suited for just an inspection. The reason you replace the needle and main jet nozzle is vibration wears them both. The easiest way to remove the two butterfly screws is with a grinder on the end of a Dremel tool. The best way to peen these over when re-installed is to take a piece of aluminum or steel rod 1 3/8" in diameter and 5"-6" long. Clamp that in a vise up straight and the throat of the carb is the perfect size and slides right over it. The heads of the screws in the butterfly lays on top and you take a flat headed drift punch and whack it a few times. These do not get Loctite. When peened over these screws can not come out. DO NOT try and unscrew these screws without grinding or filing the threaded part down. If you do you can easily strip and mess the threads up on the butterfly arm. The other thing not to do is try and unscrew with muscle the needle fixation screw from the piston. If you do this you will twist the screw head off and it's a PITA to get out and you may ruin the piston in the process. Always heat the fixation screw down inside the piston that holds the needle in place. It is Loctited in place and heat will release it. Make sure the butterfly goes back in the correct way. If you don't know where the punch mark goes you could it it in backwards and or upside down. When rebuilding carbs there are some do's and don'ts. I rebuild lots of carbs a year so if you need help and need it done let me know. Link to comment Share on other sites More sharing options...
Anticept Posted July 3, 2015 Report Share Posted July 3, 2015 Roger: as an addon: it's very important when dealing with those screws to have a dedicated screwdriver where you grind the end down so it's nice and fat at the tip. Those screws have a thick slot. The better you get a screwdriver to fit the slot, the less chance you have of damaging them. I almost never have to heat pistons because I made a screwdriver that fits those screws like a glove (and I don't use more than a couple drops of locktite, that helps too! Link to comment Share on other sites More sharing options...
Roger Lee Posted July 3, 2015 Report Share Posted July 3, 2015 Hi Corey, Wait till you twist one off. You'll be a convert in seconds. It only took me one and now I heat them all and they unscrew easily. Link to comment Share on other sites More sharing options...
Anticept Posted July 3, 2015 Report Share Posted July 3, 2015 I already have twisted one off. Tried the heat thing too. Got it over 350 degrees at one point. Still twisted off. Then LEAF reminded me that they always have a dedicated screwdriver to deal with those damn screws and to get them to fit best as possible for best results. Also, having destroyed one, I now know when too much muscle is required and have to switch over to the heat gun Link to comment Share on other sites More sharing options...
Roger Lee Posted July 3, 2015 Report Share Posted July 3, 2015 I use my small butane torch and aim the flame down into the piston area right at the screw. Works like a charm and zero muscle required. The Loctite they use is medium blue. They all come out without any force. I do about 20 carb sets a year and haven't had any issues. Link to comment Share on other sites More sharing options...
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