Engine start issues

Perhaps you might give us a detailed description of your starting technique ??

Turn on the mags and start. That’s all. Won’t start no matter what. Only way it starts is if I turn the fuel valve off and then once it starts I put the fuel valve back on. 

Hi Ofek

OK so you have established the carbs are flooding from the sounds of it.  Who installed the parts on the carbs?  What is the adjustment like on the float level?  Rotax does not make "blue" floats so they are aftermarket.  Weigh them as sets, they can't be over 7 grams for the pair.  if you changed the inlet needles on the float arm the seat should have be cleaned and inspected for any fuel varnish, this could hold them open and cause what you describe.  It might be best to find an iRMT in your area that can help you work the problem as there are many questions that should be asked to help you. 

Cheers

so I did the work as it’s not rocket science. If I can rebuild a car engine carb I can do this one as well with complete accuracy. I was told by many people that Rotax had a problem with their floats etc etc and to get the blue ones. These weigh 5.2 grams. The ones I took out weighed 6.4. I know still within limits. The seat was cleaned and inspected and all looks like new and no residue or any deformations. Both carbs showed no signs of any issues. 

yes they are flooding hence why it starts when I close fuel valve. 

Ofek

OK so what is your fuel pressure then?  Do you have an electric boost pump and what mechanical pump is your engine fitted with?  In addition do you have a fuel return line in the system, if it is blocked this may be an issue as it may go over the limits.  

Check fuel pressure, check the return line orifice is not blocked.  Some information on the installation might help, such as the aircraft make and model and if it is modified in any way.  any additional information would help, someone may know that aircraft make and model and be able to offer better suggestions. 

Cheers