i have a 1979 xs1100.the carbs have been stripped and cleaned.the jets,needles,float valves and housing,gasket etc have all been replaced.the tangs on the floats have all been lightly cleaned up to rid any wear.the floats were tested for leaks,all ok.the float heights are all set as yamaha manual to26mm. if the carbs are tilted with bowls off it looks like all the valves are working and are closing.each valve has its own filter so no dirt is present.when the carbs are fuelled up petrol fills the bowls then runs out of main air jet at the rear of each carb.they have been removed several times and checked,no fault found.in the past what ive done usually does the trick on other bikes but not this time.can anyone out there help.thanks,

zac, October 2013

How are the float needle seats fitted ? Are they screw in type with small fibre washers or the push in type with o rings and small screws holding them in place .and are you setting the float heights with the carbs upside down and with the float bowl gaskets off as this is the way to do it.if the float needle seats have the o rings I have seen them leak before as the fuel runs past the outside of the needle Sat and the needle has no way of stopping it.sadao if so try new ones.let me know zac

adam bike doctor, January 2014

thanks for info westcountry.

zac, October 2013

Hi,
These are notoriously finicky.
Here's a link to a very good site.

http://yamahaxs1100e.wordpress.com/2010/01/30/rebuilding-the-carbs/

Cheers now

westcountry, October 2013