norfolknchance
Sheene Gold rider. Nuff said
15967 mile & climbing
Posts: 783
|
Post by norfolknchance on Jan 28, 2013 19:41:05 GMT 1
CARB VENTING
As we have now seen, the CV carb needs the presence of outside air (at atmospheric pressure) inside the carb for several reasons:
--Outside air is needed under the diaphragm to push it up. --Outside air is needed above the fuel in the float bowl to push down on the fuel and force it up past the various jets and into the starting, pilot and run circuits. --And outside air is needed to service one or more of the air jets that reside inside the carb body..
How does this outside air get in? It gets in through the breather pipe which sits toward the top of the carb just under the diaphragm. Air jet(s) also reside in this space and have access to it. And drillings in the carb body allow the outside air to go down and enter the space above the fuel in the float bowl.
A breather tube typically attaches to the breather pipe and extends to some point (e.g., behind a side cover, or inside the aircleaner pod) where the air is relatively calm. Why? We don't want wind to be changing the airpressure at the end of this pipe, because this will disturb the operation of the air jets, the diaphragm, and the fuel delivery. These functions need consistant outside air pressure to work properly against the various levels of depression created in the bore, above the diaphragm, etc., as the carb goes about its work.
|
|
norfolknchance
Sheene Gold rider. Nuff said
15967 mile & climbing
Posts: 783
|
Post by norfolknchance on Jan 30, 2013 21:07:46 GMT 1
today i tried an expriment i changed the airbox to one with a filter...........motor now has a deeper note to it then disconected one sub-filter pipe from carb..........now is very hesitant at 2500 rev
flat out am getting 80mph
one day i'll figure the problem out
|
|
pikey
Bad ass biker
Posts: 342
|
Post by pikey on Jan 31, 2013 9:25:01 GMT 1
You don`t normally run a filter element? Disconnecting the sub filter hose shouldn`t have such an effect as it`s atmospheric pressure is it not, surely there should not be any great vacuum through the subfilter that will act upon carb functions? The engine / crankcases breath through the subfilter, if anything the motor should rev more freely with the crankcases venting to atmosphere and not through the fuelling circuit / carbs.
|
|
norfolknchance
Sheene Gold rider. Nuff said
15967 mile & climbing
Posts: 783
|
Post by norfolknchance on Jan 31, 2013 22:44:41 GMT 1
i ment sub-filter.....not air filter sub filter is only connected to the carbs & from what i can tell help to control the diaphragm
even without the foam filter it has to get out the filter box where as being open pipe its free to exit there must be some form of back preasure
3 carbs with different jet setups 3 airboxes........6 months later it still runs shite fingers carbs & airbox & it runs great
from what i can tell & describe as when i open the throttle at 2000rpm & close & open at 6000+rpm the slider open quick (guessing no back presure) so it stutters untill it gets the correct fuel
ive tried adding 2 layers of foam......that was even worse......restricted it too much
|
|
sear
Bad ass biker
Posts: 302
|
Post by sear on Feb 2, 2013 20:22:58 GMT 1
How does it run with fingers' airbox and the carbs from the d'ville? Then you can work out whether the problems in the airbox or if its unrelated?
|
|
odie
Bad ass biker
Posts: 263
|
Post by odie on Jul 25, 2013 19:32:37 GMT 1
I keep hand info, had this for a while now, might help you. Rick
|
|