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Post by nash2time on Jul 21, 2020 15:57:47 GMT -6
Howdy y'all. I've seen the threads for the CV tuning and skimmed most, if not all, of this amazing board but I am still struggling a little in terms of understanding a double-carb setup. I understand the basics of a carb (I've worked on mopeds with singles) but I'm not used to the double setup. My 454 currently runs pretty well, though the brakes are currently tore apart, but I just want to make sure I'm maximizing my carb for performance, mpg, etc.
So far I have cleaned out the carb, adjusted the valves, cleaned out the gas tank, replaced spark plugs, and done a number of other things. Can someone give me a simple version of what to adjust on the carb to make sure she's running like a dream? Really I just want to know where the screws are and how they need adjusted. I know the black knob screw is the idle and should only be messed with at the end and when warm. I know where to find the air/fuel mixture screws on the bottom of each carb in that super awkward place to reach but when should those be messed with? Are there any other screws than the black knob and air/fuel?
Apologies for the cluelessness. I just figured I would herald your guys wisdom rather than continue in frustration.
Thanks for any help in advance!
Sincerely,
Nash
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Post by knoizy on Jul 21, 2020 17:32:16 GMT -6
IIRC on the stock 454 carbs once you rev up past the idle circuit there's only the sync adjustment left in the equation (youtube has a million carb sync vids!) so if you've not noticed any bogging or power issues above 2k RPM that's probably a good sign.
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Post by adarngoodjoe on Aug 27, 2020 22:23:24 GMT -6
MotorcyleMD has a carb sync video based on visual inspection rather than vacuum. It's not hard to do and should get you close enough to not notice anything if it's not quite perfect. There is a screw where the two butterfly valves connect in between the two carbs. You're really just adjusting one based off the other which is adjusted by the idle speed screw. Seems like I backed the idle speed screw all the way out before adjusting the screw between the two carbs and then reset the idle speed afterward. There should be several springs in the linkage that connects the two butterfly valves. Other than that, the only other adjustment (besides idle speed) is the idle air mixture screw.
Assuming you, like me, replaced the o-ring on the screw (Should be the screw,spring, small flat washer and o-ring....look at a schematic to be sure.), I've adjusted my screw between 1 3\4 and 2 1\4 turns out from lightly fully tight. Any further out on my bike tends to result in the the bike holding revs longer rather than dropping quickly back to idle. 1 3\4 to 2 seems to be ideal all around for my bike. My factory manual doesn't list a setting for US but starts at 1 3\4 turns elsewhere. If you're a higher elevation it starts at 1 1\2.
When it's set correctly (assuming all else is well with your carbs), your carbs should rev instantly and fall nearly at the same speed. The rise and fall along with the idle should be fairly smooth. I found that when my mixture screw is too far out, revs tend to take longer to come back down and there's a brief slight dip in the revs before the climb up. The insulators on my plugs to turn a darker brown than when I run a leaner setting as well. Make sure you have good diaphragm springs and that both diaphragms feel and operate the same during their rise and fall.One of mine was oxidized from old gas so I had to clean it up and polish it a little.
You're igniter (or CDI as it's also called) can also affect how well your bike runs especially on a cold start. I've found mine almost needs to be warmed up to operate correctly. I currently have a new digital one on the way. I think my factory unit is on it's way out. I baked mine one day (at like 250-300 degrees) thinking it may have had some moisture built up in it for about 30 minutes. When I plugged it in after letting it cool a few minutes, I couldn't believe the difference in how my bike ran. When I did my next cold start, I could tell it was back to operating as it was before until it warmed up. If I don't let mine warm up for a minute, it will occasionally kind of cut out and back fire if I stay WOT as opposed to rolling off the throttle due to it not firing correctly for whatever reason.
I've found my carbs to be very vacuum sensitive when it comes to fuel delivery. Namely, I'm talking about how much air is drawn through the carb with a factory air box. I prefer the Kawasaki filters to the generics like Hi-flo or whoever. I can't speak to the pod filter type setups. I think they tend to require a lot more tuning to get them to work correctly. My bike tends to average about 45 MPG or so.
Hope this helps.
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