Adjust it and see. Have you NOT used the sync screw adjustment yet?Tickover screw is fully backed off and right carb butterfly closes but left can fit a 004 feeleblade under itwould the balance / synchronization screw cause this??
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Update on my insanity and other carb related issues ;0)
- Thread starter T250tut
- Start date
T250tut
XS650 Enthusiast
Yep - balance set with vac gauges at 3000rpm cos I can't get a tick over steady what I'm not sure about is the effect of the butterflies not closing to a sealed fit but having a gap - ???
Eyeball balance looking through the bores, install and run, see how it acts.
valves cam chain timing etc. all double checked?
Needs an orifice to quell the high fluctuations in vacuum.
Many/most automotive vacuum gauges have a twist type valve as part of the hose connection, slowly tighten the valve til the needle stops wavering but still responds to changes.
Myself, having broken vacuum guages through excessive pulsations by not having a valve closed on the gauge inlet when starting an engine - I propose best to fit the gauges with a valve closed on the gauge inlets. Then start the engine and open the valves on the gauges bit by bit to get a vacuum reading. Open them until the gauge reading is flickering too much and close them slightly to calm them down. That's your reading.
Absolute gauge reading isn't important, cylinders reading the same is the desired condition.
That way, you won't damage the gauges from excessive pulsations on starting the engine with them connected.
Absolute gauge reading isn't important, cylinders reading the same is the desired condition.
That way, you won't damage the gauges from excessive pulsations on starting the engine with them connected.
T250tut
XS650 Enthusiast
Quick update - well thats f**ked the job! 3 of the screws holding the butterflies came loose and 1 butterfly centered one screw however came half out and snapped 
so carbs off to a local engineering firm who have a 2 week lead time due to workload 
anyone got any cheap bs38s going spare?? I can swap all the new goodies from mine 
The only positive is they needed serious work any way - whatever i did i couldn't get the butterflies to seal shut and at best.could get a .004 feeler blade in the gap
so carbs off to a local engineering firm who have a 2 week lead time due to workload anyone got any cheap bs38s going spare?? I can swap all the new goodies from mine The only positive is they needed serious work any way - whatever i did i couldn't get the butterflies to seal shut and at best.could get a .004 feeler blade in the gap
It's possible the shaft is bent or the bore that the shaft rotates in is badly worn. The shaft is only chrome plated brass, not strong at all. An engineering shop should be checking all that out for you anyway. Don't forget to fit new shaft seals when you rebuild the carbs.Quick update - well thats f**ked the job! 3 of the screws holding the butterflies came loose and 1 butterfly centered one screw however came half out and snapped
The only positive is they needed serious work any way - whatever i did i couldn't get the butterflies to seal shut and at best.could get a .004 feeler blade in the gap
I had so much trouble with old BS38s, I swapped to a set of CVK 34s off an ER5. Runs great.
