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Discussion Starter · #1 ·
Finally got everything mounted up and took the girl out for a ride, and everything was fine for the most part. There was one nagging issue...no performance at full throttle! The engine responded beautifully at other throttle positions, as near as I could tell, but cracking it wide open caused a massive bog in power. I have no check engine codes and the bike idles just fine. Weather is a bit chilly, but that shouldn't adversely affect performance after warm-up in my experience. Anyone got tips for me?
 

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Discussion Starter · #3 ·
i havent added a blessed thing, just finally got all the parts bolted on to the wrecked bike i've been rebuilding.
 

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what map is on the ECU?
does it sound like the engine can't keep up with WOT? any chance you have a video?
 

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Discussion Starter · #5 ·
I'll see what I can do about snagging video. Not sure what to say about the engine "can't keep up". I've done a poor job explaining, to be sure. Basically, it builds revs in a fairly linear fashion in response to increases in throttle. Once you're at or near full throttle, though, the engine doesn't increase revs as though the throttle is wide open. It's almost as though only 10% throttle is applied. I suspect a fuel issue, I just don't know where to begin. The map loaded when I got the bike is labeled 20137. I couldn't tell you if that's a custom map or not, honestly.
 

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from the sounds of it - it probably is a fuel issue. is there any rust in your fuel tank? a dirtied fuel filter maybe? are the injectors clean?
 

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If it was carb'd I would point to the main jet.

I would see if the fuel system is all clean, and your fuel pump is still strong.

Might try resetting your ECU.
 

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Discussion Starter · #10 ·
Intake flap and exup removed, tank is clean as a whistle. Is the pickup on the pump the only filter or is there one later down the line outside of the tank itself? The air filter is also clean and I don't believe it's a vacuum issue since it idles smoothly.
 

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When you removed the Flapper did you cap off the vacuum hose? did you load a new tune on to the ECU to account for the lack of EXUP and Flapper?

Just because it idles fine doesn't mean there's not a vacuum leak, it's still possible.

The flapper is vacuum operated, and doesn't open until a certain RPM defined by your tune. if you've disconnected the flapper and left the hose unblocked it won't cause any issues until you hit the RPM that the flapper would normally be activated.
 

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Discussion Starter · #12 ·
EXUP and flapper are disabled in the ECU. Is it still necessary to cap the vacuum hose even with the appropriate settings made in the ECU?
 

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EXUP and flapper are disabled in the ECU. Is it still necessary to cap the vacuum hose even with the appropriate settings made in the ECU?
Probably,
If you've removed the flapper and the vac canister/solenoid you've got a vacuum leak.
 

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Discussion Starter · #14 ·
I didn't remove any of the hardware, I'm just trying to work my way through what was removed before my ownership. Sounds like I need to start working through some diagrams in the service manual to trace back what's missing.
 

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Discussion Starter · #15 ·
Flapper wasn't the culprit. I plugged the vacuum hose and the behavior hasn't changed, unfortunately.
 

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Discussion Starter · #16 ·
Quick update: a fuel pump replacement did fix this last year, and the bike was running fine when I parked it. Annoyingly, the problem is back. I tried mounting a different tank and fuel pump, but the problem persists. I'm at my wit's end here. It ran fine all track season, and now I'm back to getting the damn bog when I crack the throttle. Help?
 

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Discussion Starter · #17 ·
More new stuff: performance improves depending on the map utilized, but I still can't get proper response from large throttle openings. Hoping to get a video today to demonstrate.
 

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Did you safety wire the exhaust valve open? The spring on the valve holds it open, if you physically turned it and wired it there, its closed. Might not be your issue but ive seen this before. The bike wouldnt go past roughly 8k at WOT, if i slowly rolled the throttle it would climb rpm but slowly. Hope this helps!
 

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Discussion Starter · #19 ·
The Leo Vince full system I have doesn't have an exhaust valve and I disabled that in the map using TuneECU. It doesn't seem to matter what RPM it's at when I crack it, though. If I whack it open it just falls flat.
 

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Sounds like a fuel issue. Considering youve tried multiple tunes with no success i would start looking at the fuel system.

EDIT - Just saw youve tried a new fuel pump and tank with no success. Time to go deeper. Maybe injectors. Maybe trash restricting flow after the pump.
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