En500
 

Hi, Looking for some inspiration here, have a500EN '90 with CVK34s starts runs to about 2krpm, then fuel starvation (?) choke hardly helps, carbs cleaned many times,all good, runs up about 1/4 throtthle then gasps and slowly dies, sparks all good checked with timing light, .float height 17mm , fuel level +.5.. over.base.. Manual says keep vent tube away from intake, upsets etmosphereic balance in float chambers, but no matter what|I do it's the same. Is this designed so that the air resistane in the factory airbok/element is so critical to mixture? ` am attempting to run individual cone cleaners. , getting adequate flow thru tap, . - like geoff boycott, I'm Stumped...... any ideas please?
Best Regards all Paul Milsom