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Tuning help


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So I just got a freshly built 421 banshee. It starts up and high idles but once you put it in gear the idle goes back down to normal. Then when you go to get on it, it sounds like it’s sputtering and when you get all the way to 6th, it sounds like it’s turning off and on. New spark plugs. I synchronized the carbs today and i got the idle issue fixed but it’s still running horrible. 

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It idles fine and it will respond to throttle in nuetral and it’s crispy. But when you put in gear it doesn’t have the power that it should. I tried posting a video. But the video is too large

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Who assembled the engine? Did it get leakdown tested? High idle can be cause by an air leak….. and considering it’s a new motor….. it may be lowering the idle when in gear because of slight mis-adjustment on the clutch side of things

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You may be on to something with the mis-adjustment. Because when it’s running you can’t put it back into neutral. Bring home an ohm meter from work so I can rule out the stator. 

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17 minutes ago, Jereme6655 said:

Who assembled the engine? Did it get leakdown tested? High idle can be cause by an air leak….. and considering it’s a new motor….. it may be lowering the idle when in gear because of slight mis-adjustment on the clutch side of things

Also, it passed the leak down test

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  • 2 weeks later...

Update:

-Carbs are synced
-New dynatek coil
-Noticed that the bowls were on the wrong carb. Swapped them
-Installed choke equalization tube

Starts up first or second kick. Idles fine. But still bogs under a load.


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 Check your wiring harness to make sure it’s not grounding out anywhere and check for broken wires or loose connections. Also if you have a friend that has a banshee try swapping out the ignition coil. Even though it’s new they can’t be trusted especially when it comes to aftermarket coils. When it comes to electrical parts it should only be OEM. 

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I went and put a couple runs in yesterday. I put 320 mains Instead of the 340’s. It sounded crispier at idle but it’s still doing the same thing. I put my hand on the right exhaust while cruising and there was flow but nothing like the left exhaust. I got a video of it. Wish I could post videos on here lol


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