Guest hatrack Posted February 16, 2008 Share Posted February 16, 2008 G'day. Have just bought a new 503. Can't seem to start it with the hand choke levers. Have resorted to the trusty old squirt of fuel down the plug hole trick (which works). Have also got a flat spot if I give it full throttle too quickly, from which it takes ages to sort itself out. It gets flooded and will not rev past about 3000 rpm. Only by tickling it around 2000 to 2500 rpm can I burn up the excess fuel and get it sorted. Then it runs sweet. Any gurus out there? Link to comment Share on other sites More sharing options...
Knighty Posted February 16, 2008 Share Posted February 16, 2008 Hi Hatrack Dont know about being a guru but have a rough idea how things work in the big picture of things! 1: Choke will ONLY work when the throttle is closed because of the carbs design. A simple priming trick without taking anything apart is to lightly blow a small mouthful of air into the clear tube that comes from from each side of the carb (Atmosphere Equalisation). Doing this fuel transfers directly into their throat. My 582 loved this on a cold winters day and it fired up after one revolution, you dont need to spend a cent on priming gear or taking spark plugs out or air cleaners off. 2: Fuel bowl level is measured when the carby is full of fuel as per normal running. Take off your bottom bowl and measure the fuel from the top, this should be between 1/2 inch to 9/16 inch mark from the top. As for the dead spot I have never experienced any of this on the Bings and numerous motors I have worked on. When you experience the the dead spot I would suggest to shut the motor down immediately and check that fuel bowl level. It sound like to me your motor is BOGGING DOWN. You may need to replace the needle (cant think of the proper name, its 4 in the morning and I cant sleep, bugger) as it has a soft synthetic end on it and if its not closing off when the floats are telling it to then excess fuel and a high fuel bowl level would be the result and flooding would shortly follow until the system is clear. This sounds pretty much what you have explained yeh? Also another point that needs to be made is the carby design only requires a low fuel pressure, if you have a secondary electric fuel pump this may cause a few problems. Give me a post back when you have looked over things. Also I must add your little 2 stroke relies on good fuel management for performance and reliability. Ive always run my motors according to the EGT's, if you havent an EGT BUY ONE as it can save you $$$ not to mention that safety factor etc. Cheers Knighty Link to comment Share on other sites More sharing options...
Guest hatrack Posted February 16, 2008 Share Posted February 16, 2008 Thanks Knighty. Very prompt! Mate I know about closed throttle with choke, you need it for vacuum, and have always done that. Thanks anyway- it would be an easy mistake. That trick sounds handy with the equalisation lines. The engine only has 4 hours on it so I would hope the needles are fine. And one would think that the float level would be right from the factory. But I know I will have to eliminate them. Mate they tell me that the Bingg carby doesn't have a choke but an enricher. Do you know exactly how they work? Do you know of any websites detailinging Bing carbs? The Rotax manual doesnt show much. And yes I have dual EGT which I glance at every minute or so. I blew holes in 2 pistons with my old dual point 503. It had Mikunis and I was never confident fiddling with those. Cheers. Go back to bed. Link to comment Share on other sites More sharing options...
Captain Posted February 16, 2008 Share Posted February 16, 2008 G'day. ...... Only by tickling it around 2000 to 2500 rpm can I burn up the excess fuel and get it sorted. Then it runs sweet. Any gurus out there? G'day hatrack, No, No gurus. And it's impossible to come to a conclusion from your initial few lines, but based on racing 2 stroke bikes, it sounds a bit rich or cold when it fluffs at 2000 - 2500. What colour are the plugs and are they in good nick? Regards Geoff Link to comment Share on other sites More sharing options...
Knighty Posted February 19, 2008 Share Posted February 19, 2008 Mate they tell me that the Bingg carby doesn't have a choke but an enricher. Do you know exactly how they work? Do you know of any websites detailinging Bing carbs? The Rotax manual doesnt show much. Yes you are right about the enricher circuit, I have seen the breakdown on how the carb works but have looked through my books and cant find the info anywhere. I have however a breakdown of the carb parts in my California Power systems book, I can scan the pages for you and email them if you like? Give me a pm with your details and I will email you the pages if thats any good. Cheers Knighty Link to comment Share on other sites More sharing options...
slartibartfast Posted February 19, 2008 Share Posted February 19, 2008 There's a few diagrams and a lot of info about the Bing in the Jab 2200 manual here. Link to comment Share on other sites More sharing options...
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