vfr400 nc24 rich and revs hang

[Persicus]

[img]c:\users\chris\nc24.jpg[/img]

[Persicus]

i wud post some pics but i cant seem to do that on this forum for some reason.

[hunter]

You need to use photobucket or simular.

[magg]

Nothing to loose, try no air filter. When did problem start, after the non standard air filter fitment. Richness might be flow restriction and hanging idle could also be some weird affect from the non standard filter.

[Persicus]

magg, i suppose it did start after putting in air filter, but then the carbs were also all cleaned and reset to standard settings, on another point i never actually checked what size the main jets were (standard 112? 115?) so this could cause over fueling i suppose. will have to take em off again and check.

[Persicus]

ok again another update,..............
carbs off again checked All jets and sizez. 115 main all round, 35 pilot all round, redone float heights, 6.8mm all round. carb sync.......hhhmmm....te main carb with throttle attachment wont close fully, ie can see light through butteryfly when all others are set to just see the small hole in venturi, this could point to revs hanging????? if so what can i do as you cannot adjust this the close it off!

[magg]

As you are no doubt aware, the carby throttle valves are mechanically individually adjustable. The "main" carby adjustment is the idle setting knob. Do not understand why you cannot adjust all four to operate in unison, unless one or more is damaged.

[Neosophist]

This is something i hadn't taken into consideration but it sounds like the carbs are really out of balance.

If they are way off this can cause hanging but i dont see how it will cause them to run really rich.

115 all around is stock for NC24.

Perhaps the carbs are incorrectly assembled.

You have the main idle adjuster screw which will move all 4 carbs and 3 screws underneath that adjust the individual linkages to adjust balance, these should be adjusted with carbs on engine and balance gauges attached, have you adjusted them?

[Persicus]

had manually balanced the carbs on the bench following instructions from rick oliver (using the small holes in the throttle body as a guide mark), havent got access to any balance gauges so thats why i sued that method.
i did notice the main carb even when on throttle stop the butterfly wasnt fully closed, (only a fraction) could get all the others bang on but not that one (only taking fractions of a mm but i suppose this could cause an issue.

[Persicus]

okay then guys, another update. reset all the carbs again (and again and again and again!) checked all for air leaks, none found, however i did notice that the choke on the front two carbs wasnt closing fully (just about 2-3mm to seat back properly), have now modified to a solid bar rather than a cable to come out of the side so it has no play and now shuts all the way off.
This could be why its running rich, also turned the a/f screws to 1 3/4 turns out.
started first time with choke and idled fab, took for a spin to get warm and the hanging revs have improved dramatically, still pulls through the gears nice so all i can do now is get hold of some balance gauges and do a final tweak. the revs still hang a tiny bit but no where as bad so hoping a fine balance will sort this out.
will post back when i have got hold of some gauges.