I fit DOT head in b12, run on mikuni BST 36 preaty much well.
So I start setting mikuni RS 38. Set as should be, main 135 pilot 17,5 idle 2nd form top, fuel level 17mm. Been balanced. Running terrible at low and mid. I discover that mixture screw at 1 whole out improve reaction at low rev... But worse thing is that it stops at hi revs and very slowly drops. I's pretty scary when it hangs at 6tou at 3nd gear and it don't want to stop.
have you fitted a push/pull throttle as these carbs have been known to stick open due to the air pressure on the slides . also you might need to go up a size on pilots and raise the needle the factory settings are just a starting point and usually not far out
I had a lot of problems with rev's hanging up and misbehaving like you describe with a set of BST carbs. Turned out that the inlet rubbers were leaking air past the O-ring seal between the head and the rubber. Its worth a look, I spent days trying to chase fueling issues that turned out to be air leaks and bad sync.
does sound like a vacuum problem. also the intake ports need to be 'opened up' to work with larger carb boots on dot head. using dot head intake boots? or later/larger boots? if you mount them and look in the port you can see what you have to remove. this will cause a reversion effect, intake charge back into carbs, especially at lower rpms.
revs hanging up means mixture is lean try turning screws out 1/8 at a time till drops back quick ,or set with colour tune or vac gauges, as for mains all bike are different even with same setup but could put you a lot closer
Hi, first check cable for free movement,137.5 mains with dublex filters are too small, 150-155 is more like it. Check for faulty air, set mixture screws 2 out, on working temperature, let her idle, then turn screw on no 1 in till rpms drops a bit then turn the screw out a full turn, try that on all cylinders, keep in mind that all mixture screws have to have the same amount turns out.