OK, let's clarify needle terminology as it applies to these Mikuni carbs. First, the clip slots on Mikuni needles are counted from the top down .....
To lean the needle, you need to lower it in the slide, to make it richer you need to raise it. This is what's confusing - to lower (and lean) it you have to raise the clip up, to raise it and make it richer you have to lower the clip .....
Now I'm going to go back to the needle jet. You really haven't clearly answered about that. You said you bought new Mikuni jets from Niche Cycle but I checked their site and they don't sell the Z-8 needle jet your carbs require. They only sell Z-6 and Z-2 needle jets, both of which are leaner. If you did get some of those, that could be your problem. Your stock 4M1 needle is made to operate correctly when paired with a Z-8 needle jet. Even if you didn't change the needle jet, maybe someone before you did and installed the wrong ones. It's probably best you check them to insure they are the correct Z-8's. I'm kinda hoping they're not because it would help explain your issues.
Then I guess it's also possible that you don't even know what I'm talking about when I speak about needle jets. They're the long tube that the needle sticks into. They're not a small brass screw-in type jet like the mains and pilots .....
To lean the needle, you need to lower it in the slide, to make it richer you need to raise it. This is what's confusing - to lower (and lean) it you have to raise the clip up, to raise it and make it richer you have to lower the clip .....
Now I'm going to go back to the needle jet. You really haven't clearly answered about that. You said you bought new Mikuni jets from Niche Cycle but I checked their site and they don't sell the Z-8 needle jet your carbs require. They only sell Z-6 and Z-2 needle jets, both of which are leaner. If you did get some of those, that could be your problem. Your stock 4M1 needle is made to operate correctly when paired with a Z-8 needle jet. Even if you didn't change the needle jet, maybe someone before you did and installed the wrong ones. It's probably best you check them to insure they are the correct Z-8's. I'm kinda hoping they're not because it would help explain your issues.
Then I guess it's also possible that you don't even know what I'm talking about when I speak about needle jets. They're the long tube that the needle sticks into. They're not a small brass screw-in type jet like the mains and pilots .....
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