7/64" drill is what I think I used for the diaphragm.
That explains a lot. It hasn't been liking the throttle since I installed the N65C with either the 180 or a 175, Was thinking of putting the N86E back in with a shim or two, to see how it changes things.That's only the N65 needle, the rest of the sporty specific needles are thicker.
The first CV's used on Sporties were sans accelerator pumps, and they used that rapid taper needle to make up for it.
Dropping it into a big twin will fatten them up. But usually fattens them more than they need. General rule is N65 - 165 Main jet - 42-48 Low speed jet.
That needle jet is sort of just there. You jet the carb from the bottom up, after you select a needle profile. If you look down the bore you'll see some little holes that the throttle blade uncovers as it opens. The first one is controlled by the idle screw. The rest of the holes are controlled by the slow jet. The jet sets the maximum amount of fuel that the combined holes can flow. The holes split the flow (stage) and as each is uncovered by the blade, the flow from that hole is added to the total. There is also air that gets sucked into the fuel passage through the air jet. The air jet is not field adjustable, and it can suck in dirt. A tiny speck can totally screw your fuel flow. That's why you never run a CV without a filter. And that's why at idle, the throttle blade should not uncover the second hole. If it does, you need to drill a bypass hole in the blade so that you can close the throttle to cover that second hole. The thing to remember is that the slow jet fuel is always there. If you change the slow jet, you change the fuel on the top end too. That's why you tune from the bottom up. Tune the first 30% of the throttle twist first using the slow jet.That explains a lot. It hasn't been liking the throttle since I installed the N65C with either the 180 or a 175, Was thinking of putting the N86E back in with a shim or two, to see how it changes things.
I have a 165 I can get from my buddy though, so may toss that in there before going back to the N86.
I haven't cut the spring, but the slide was already drilled to 1/8" and I backed out the idle mixture to 2 1/2 turns from fully seated.
Some comments made above in Orange,That sounds like great info.
I will say before I write more that I am becoming quite frustrated and confused at results. That is to say that all needles are now richer than they were when I started, yet my pipes are blueing now. Isn't that a sign of running lean? The needle is not having any effect until after it lifts out of the jet. And that is not until you are at about 1/3 throttle on steady cruise. The pipe blueing can be because its lean, or it can be because the spark advance is slow and it can be from an air leak at the spigots. And some pipes just seem to blue because they can. Letting the scooter cold idle at 1500 for more than a moment will blue them for sure.
I began this morning, after a warm up ride, with the goal of starting at the bottom (as I understand it) and working up. So I attempted to start with the idle mixture. Following instructions on nightrider, nothing seemed to go as it was supposed too. Clockwise until the screw was set caused no change at all to the engine that I noticed. Backing it out eventually (3+ turns) caused it to run rougher, but that is the opposite of how I understand it is supposed to act. If the idle mix has no effect, 1) check that only one transfer port is uncovered at idle. 2) Be absolutely sure there are no vacuum leaks. 3) reset your float. 4) make sure the idle passage and air bleed passage are free of debris. And while the carb is on the bench, look at the idle port opening. If its raised up from the screw being more than lightly bottomed out, the carb body is junk. 5) Be absolutely sure that the enricher is closed when you push the cable in. The valves and seats do wear out. Fix this idle issue first. Don't even think about the rest of it untill after you have control of the idle setting.
So how does that figure in? Am I really richening or leaning the carb from top to bottom if there is no indication of either at idle? Is it that idle mixture screw big of a deal? That video of Scotty's even mentioned that it doesn't seem to affect hardly anything, and to just back it out 2&1/2-3 turns. That's it. NO adjustment based on how the engine is running. Maybe I need to back it completely out and give it a look? Not that I know what it should look like. I can compare it to the ones from the other two CV carbs I have though.
Installing the 48 pilot seemed to clear up the popping and such on decel (at least that is what I think did it), at first. Riding it more, I can still say it is much, much better. Although I am seeing some, most notably starting when I get down to between 3500 and 2500+ RPM, Below that I am not noticing it. That is well below 30% throttle though.... so is that a slow jet issue? Do I need to upsize it again? What would that be.... a 50? That's starting to get a little rich, right?
Another issue.... just trying to hold it steady, say at 2500 rpm (35 mph-ish) it runs pretty rough. AS was mentioned.... kind of stumbling or skipping.
This would likely be much easier on me if I was better at recognizing how it acts riding lean as opposed to rich.
I didn't notice any issues on WOT, or even hard throttle, but did not spend a lot of time there today. I did open her up a couple few times for short burst, and she seemed more responsive to me than ever. Smoother. Better pull. Sounded better. The original Main Jet that was in it when I started was a 175. Again, I'm at a 180 now.
A question on the needle profile. Doesn't adding washers to shim it up also enrichen from top to bottom? I mean, It allows fuel to be drawn from the main jet from the very beginning, as it is never really closed, right? Or is there something I am not quite grasping on this? I can be thick at times.... Would that possibly account for why the idle mixture screw seems so inconsequential? That is, the carb is now sucking from the main what I closed off with/from the idle mixture screw?
Also on the Main & Needle combination. I understand (I think) what is being said about how the Main is for WOT, but won't it also affect the midranges also, as with a needle being the same size & at most any given height... a larger main will allow more fuel to pass than a smaller?
I'm not intentionally disputing anything @Thermodyne has mentioned. Am just trying to gain a better understanding of what was said.
Thanks. You posted this while I was writing my response to the other replies. Thanks again for all your info and help.Some comments made above in Orange,
I would add, that some carb bodies get dirt packed into the air bleed system that no amount of spray cleaner and compressed air will remove. Sometimes caustic dipping will take care of it, and some times the air jet needs to be pulled so you can take a wire brush and torch tip cleaner to the passages. Me, I would grab another carb before I went to as far as dipping it. Past that, make sure the carb body is intended for a big twin. Those 880 carbs never seem to work well on 80 inch motors.
And to close, I have never seen a chrome Thunder header that didn't blue the primaries. That pipe is designed for the drag strip. WFO and damn everything else. They are also a bitch to tune in the intermediate range with a carb. The Thunderjet was a response to the need for three fuel circuits to tune them. Back when they were popular, the old dyno guys would usually tune the top and bottom at the carb and then work on the baffle to fix the mid range.
Are you working on this carb with it still installed on the bike? If so Why? Take it off and do it on a bench so you can do it easily. Small Vice grips should (vice grip brand not cheap junk knock offs) should get that screw out if head is striped. I never seen anyone put locktite on one .Have tried most of what I knew, using a Phillip's tip and a 1/4" ratcheting screwdriver to fit in straight between the screw head and the jug. Tried grabbing it with vice grips from the side and turning, but no luck. I'm thinking the previous owner used red loctite. I'm hesitant to use a flame anywhere near the carb, but may have too. I saw a video where someone used chlorinated brake cleaner that broke down red loctite, so will try that next, before moving on to my little butane soldering iron torch. Then I would have more freedom of movement with the cap to insure the diaphragm is seated right, after giving it a thorough inspection.
It is not about manifold Vacuum (MAP) Air flow causes the needle to lift. A separate source of vacuum is created by the airflow across the opening in the slide. This vacuum is applied to the slide diaphragm and causes it to lift. Think about it, if it was MAP on the slide, the needle would be retracted at idle and seated at wfo. Another thing to be aware of is that the needle never shuts that port off. As soon as there is enough air flow across the needle jet, it flows fuel. The needle just regulates how much. And when uninformed hands have been in those carbs, you'll some times find the jet installed upside down, or worse, replaced with one from a Kawasucky. That can be a real mess to sort out.OK. It sounds like I need to do a few things differently. No more making more than one change at a time! I knew that, but.... well, we will just leave it at that. I am, however, tempted to just start completely over....
First, The screw that holds the throttle cable assembly onto the side of the carb won't loosen. So when removing the carb cap, I have not been able to loosen it in order move the bracket off of the back right corner & lift the cap straight up. I guess it is possible I did not get the diaphragm seated correctly, but it seemed good. I need to be able to do that portion cleanly though, I am sure.
Have tried most of what I knew, using a Phillip's tip and a 1/4" ratcheting screwdriver to fit in straight between the screw head and the jug. Tried grabbing it with vice grips from the side and turning, but no luck. I'm thinking the previous owner used red loctite. I'm hesitant to use a flame anywhere near the carb, but may have too. I saw a video where someone used chlorinated brake cleaner that broke down red loctite, so will try that next, before moving on to my little butane soldering iron torch. Then I would have more freedom of movement with the cap to insure the diaphragm is seated right, after giving it a thorough inspection.
Once I get the screw out, and replaced, before I make any changes at all, I want to try that enrichener/choke bit, to verify if I am lean or rich on on that steady throttle issue around 2500... then proceed accordingly.
I'm still confused a bit though on where the needle starts to come into play. It's based on vacuum, rather than RPM, I understand. And I understand it is not necessarily an on/off or discreet type of switching. Still, Thermodyne mentioned that it is the slow jet at 30% throttle and below, or that is how I understood him anyway. 2500-3500 RPM is way below 30% on my sled. Scotty mentions that once off idle, it is all up to the needle with it's taper and height. I assume he might referring to being off of the slow jet, as opposed to off of idle. NO NO NO. Its not based on vacuum from the engine or rpm. Air flowing through the suck hole is drawn across the opening in the slide. This creates a separate source of vacuum that is localized on the slide diaphragm only. (example: Blow across the end of a straw in a glass of water and it will suck the water out of the glass. Same deal as when you use a jug of weed spray on the end of your garden hose) And this air flow is from opening the throttle blade. It does not care about manifold vacuum, just the velocity of the air flow. Think about it, it it was plumed to manifold vacuum, the slid would be up at light load and closed under heavy load.
So, how do I know what jet is 'doing the work' at that 2500-3500 RPM, and needs a little tweaking? My assumption is that at 2500ish I am just beginning to use the needle valving, and that at 3500 I am a bit more into it and fully thru the slow jet "staging", but is that really correct? Am I off of the slow jet's staging by then?
Snap On battery cable pliers is my go-to on that screw.Are you working on this carb with it still installed on the bike? If so Why? Take it off and do it on a bench so you can do it easily. Small Vice grips should (vice grip brand not cheap junk knock offs) should get that screw out if head is striped. I never seen anyone put locktite on one .
As far as checking a lot of the stuff Thermodyne is saying, yes, she needs to come off. For the jet and needle changes, there is plenty of room on the bike. Even the idle mixture is pretty easy to get to.Are you working on this carb with it still installed on the bike? If so Why? Take it off and do it on a bench so you can do it easily. Small Vice grips should (vice grip brand not cheap junk knock offs) should get that screw out if head is striped. I never seen anyone put locktite on one .
Sprayed it with some brake cleaner and let it set for an hour. She broke free pretty quickly. I didn't see any sign of loctite though. Replaced the screw with one that does not have a stripped head.Don't use heat! The rubber diaphragm and gasket will be destroyed. Not to mention fhe fuel issue. You have a dremel? Maybe try cutting the head off that screw then work on it on the bench. Wrap a wet rag around it to catch sparks.
There is one washer under the needle... about .027. Did not mess with it yesterday due to the rain. Will go back out and start tuning it again in an hour or so...Are the washers still under the main?