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I got problems!

Old 07-25-2007, 08:52 PM
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I got problems!

So, it doesn't concern me greatly, but... After doing my undertail exhaust, I have been having what appears like a rich (or ignition misfire) stumble on hard throttle at 6500rpms. Why I say its rich is that the dyno sheet shows a remarkable drop in power and a dip in air fuel ratio. My question is if anyone else has had this problem???

I have run through the scenarios in my head, coil would continue to suck ***, same with spark plugs. I just can't think of a possible solution as of right now, that doesn't cost me of course.
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Old 07-26-2007, 11:18 AM
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Post Dyno with A/F curve?
17/43 gearing?
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Old 07-26-2007, 06:34 PM
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6500 is a strange place to have a hiccup.... I see you have a drop-in.....stock airbox? Don't see why you'd have a rich dip at that particular rpm though there's something funny going on in the airbox like it's losing pressure
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Old 07-26-2007, 07:18 PM
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The airbox isn't pressurized.

6500 is when the mains start playing into the jetting equation. It's mainly the needle height and profile though. Maybe drop the needles a bit?
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Old 07-26-2007, 10:30 PM
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Originally Posted by Hawkrider View Post
The airbox isn't pressurized.

6500 is when the mains start playing into the jetting equation. It's mainly the needle height and profile though. Maybe drop the needles a bit?
+1
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Old 07-27-2007, 05:01 PM
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I know what you are thinking, 17/43 gearin???? Yeah, so I could only get the sidewinder tri-metal in a 43 tooth and didn't want to loose the highway attitude so I bumped up the front a tooth. The ratio is a tidbit shorter, but hardly noticeable. Less wheelie happy, for sure. I shoulda done a 520. Oh well,
As for the jetting. Ok on the needles coming in at the point, but the problem is that we have it dialed in right no for AFR and don't want to dick with it. I just didn't know if anyone had experienced this problem. Also, i have a goofy undertail I built myself, so I think that may be part of the problem.
thanks,
Bill
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Old 07-29-2007, 04:16 PM
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How would the undertail have anything to do with the jettting? I'm cornfused!
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Old 07-30-2007, 03:28 PM
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the lengths of the exhaust will play a role in the wave tuning and could definitely cause hiccups in a carbed bike. Oh well, I think I am going to just keep beating it like a bad dog.
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Old 07-30-2007, 04:13 PM
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Aha! Undertail EXHAUST! Got it. I was thinking undertail, as in fairing.
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Old 09-12-2007, 11:43 AM
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Thought that this may shed some light on recent tuning questions. I lost one of my homemade endcaps to my homemade exhaust. This pretty much sucks, but the shop i was working at had a shifter cart exhaust end that would work with my diameter, yeaaaaah. But wait, it only had a 1" outlet, so I tried it and it completely fixed all my carb problems. The first time I went out I hit the rev limiter in first because it didn't hiccup at 6500 and lose power. NOT ENOUGH BACK PRESSURE, i say, so its getting equal sized outputs to help this, and quiet the bike overall. Boy I am happy.
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