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Buell Forum » XBoard » Archive through September 08, 2012 » My First Buell, Flat spot at 4000 RPM « Previous Next »

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Ktmguy
Posted on Wednesday, August 15, 2012 - 08:35 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Coming from 37 years of riding and racing dirt bikes, the Ulysses felt like a large 100 HP dirt Bike.. When wife sat on back, she really liked it.. so.. SOLD!

Now that I have put some miles on it, Im learning its quirkiness, strengths and weakness, etc..
Currently, My only serious displeasure, is a noticable flat spot from 4000 rpm to about 5000 rpm.. After that it really comes to life and pulls hard.. Pulls great below that also. Makes now difference in throttle position, once the tack gets near the 4g range, I can feel it flatten out.

I did some research on this, and noticed some others had the same complaint across the web, however, I never was able to find how they got it resolved?

From what I know.
The bike, runs a K&N filter
The stock Can was modified by the same folks who do the drummer exhaust here in NC, however I dont know what was done to it, it does not sound overly loud, and pulls great.
Zero Popping in decel..
I believe I have the stock ECM, however I dont know how to tell? I dont see a EBR on it anywhere.

BUT, since I have read about the flat spot on seemingly stone stock bikes, it leads me to believe it may be a common denominator of some sort?

Any Help Appreciated!!
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Froggy
Posted on Wednesday, August 15, 2012 - 09:44 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Are you sure that it is a Drummer exhaust? The Drummer should not have the flat spot like some of the other aftermarket exhausts. Also, what does it say on the ECM?

If you could, take a picture of the ECM and exhaust, we can identify them.

Stock bikes should not have the flat spot either, they have a valve in the muffler that reroutes the exhaust flow depending on the RPM and how much throttle you are giving, preventing the flat spot.
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Ktmguy
Posted on Wednesday, August 15, 2012 - 09:51 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I do not know if it is a drummer exhaust per se.. I was told that the original owner sent the stock can to the folks and had the stock can modified? The exhaust looks stock and factory, black in color (slightly faded)
The ECM Simply has what looks like a product/ skew code on top? Ill take a picture this evening and see If I can post it. The bike pulls VERY well from about 2200 RPM up to 3800/4000 rpm. Then it flattens until about 5000 or so and pulls Very hard again.
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Sifo
Posted on Wednesday, August 15, 2012 - 11:57 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Is the exhaust valve still hooked up and operational? If the stock can was modified, they may have also undone the valve, wired it open, or who knows what.

EDIT: BTW, the servo for the exhaust should be mounted on the top of the inner air box. The control cable is routed down the left side of the engine, then crosses to the right side just under the throttle body, and hooks up to the exhaust valve on the right side under the engine, just to give you an idea of what you should have.

(Message edited by SIFO on August 15, 2012)
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Ktmguy
Posted on Wednesday, August 15, 2012 - 12:50 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Sifo, I WIll try to look at that this evening or this weekend. Very good question, and Im embarrased to say I hadnt considered that before asking for help.

Just bear with me guys, this electronic bike stuff is a bit new to me.. Im used to adjusting valves and jetting carbs. I'll get there, and thank you for the prompt responses.
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Ktmguy
Posted on Wednesday, August 15, 2012 - 02:00 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

It happens no matter what the throttle input, it is RPM regulated, not throttle opening regulated.. Whenever the tack gets near 4g it flattens noticabley.. So I will try to look into the exhaust valve.
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