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Buell Forum » Knowledge Vault (tech, parts, apparel, & accessories topics) » Troubleshooting (Poor Starting/Running/Handling/Ride Issues) » Engine Cutting Out at 4,500rpm - Everytime « Previous Next »

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Mcengnrng7075
Posted on Tuesday, June 23, 2015 - 10:41 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

My XB9 motor cuts out every time I accelerate to exactly 4,500 rpm like clock work, and it seems to be irrespective of any specific throttle position. When it cuts out there is a complete loss of power and I can't get the engine to get past 4,500 rpm. It's very similar to hitting a rev limiter were the engine bounces off the limit but in this case its only at 4,500. This comes along with some pretty good backfires. It then refuses to run properly again until I pull in the clutch and allow the motor to stall and then I can restart it and carry on (until I hit 4,500 again...) Under no load and parked I can rev the engine past 4,500 without a problem - seems that it needs some load to cause the issue. Has anyone had a similar issue along with a solution? No check engine codes. (2006 XB9-SX, 34,000 miles, no engine mods other than K&N air filter)

(Message edited by mcengnrng7075 on June 23, 2015)
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Reepicheep
Posted on Tuesday, June 23, 2015 - 08:09 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Not a perfect match for symptoms, but I'd be looking at the crank position sensor. Your symptoms are pretty close.

Easy to check if you have an oscilloscope (even a cheap one).
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Mcengnrng7075
Posted on Tuesday, June 23, 2015 - 09:03 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thank you for responding Bill. This problem has gotten worse in that the frequency has gone from very seldom to every time. Is that indicative of a failing crank sensor to go from not so bad to totally bad? I def do have an oscilloscope. Can you point me in the direction on how to actually test this?
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Mcengnrng7075
Posted on Tuesday, June 23, 2015 - 09:10 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

And to be clear we are actually talking about what Buell calls a cam sensor not a crank sensor (regardless of what its actually sensing) Is this the one: http://americansportbike.com/newdir/Item/17495
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198rock
Posted on Wednesday, June 24, 2015 - 06:28 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Similar symptoms on my 08 XB12ss... problem was the plastic intake cover collapsing against the intake boot. Mechanic resolved it by trimming the boot. The check was that it ran fine with the cover off, only had problems with the cover on.
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Reepicheep
Posted on Wednesday, June 24, 2015 - 08:08 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Correct and correct, continuing to get worse is exactly how the CPS fails. And it is actually a cam position sensor, I get lazy with my terminology. Is the tach needle also doing the funky chicken dance when the bike is running badly? That's another indicator.

Here is a good thread that shows some good detail...

http://www.badweatherbikers.com/buell/messages/384 2/712569.html?1362582842
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Mcengnrng7075
Posted on Wednesday, June 24, 2015 - 09:47 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thanks again Bill, there is a wealth of knowledge contained within that link. I can't get the problem to occur while parked and there is no way I can get my 15 pound, AC powered scope on my bike while riding at 4,500 rpm! I think I might just bite the bullet and attempt a repair-by-replacement method on this one. I'll let you know how it goes. And to answer your question, the tach does do a bit of a chicken dance but I had just assumed it was actually reading the RPMs correctly as it bucks like a bull.
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Mcengnrng7075
Posted on Wednesday, June 24, 2015 - 09:50 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Glen, thank you for the hint. While your issue certainly seems plausible, my intake cover is very rigid however I can certainly take the bike for a spin without it and see what happens. Thanks!
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Reepicheep
Posted on Wednesday, June 24, 2015 - 10:19 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Not a bad part to have a spare of tucked under the seat anyway, so at worst you refreshed a part that often fails (but didn't fail yet) and have a used but working spare on hand.

And look at this. Sorry in advance for making you spend your money. : )

http://www.amazon.com/SainSmart-Upgraded-Pocket-Si zed-Handheld-Oscilloscope/dp/B004Y3QHZ6/ref=sr_1_4 ?ie=UTF8&qid=1435155104&sr=8-4&keywords=dso+nano

(or search for DSO Nano on Ebay)

The BenF firmware is a nice (and easy) upgrade, but the stock firmware works fine also.
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Mcengnrng7075
Posted on Wednesday, June 24, 2015 - 12:48 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Okay thanks for the link.
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Gabby_duck
Posted on Wednesday, June 24, 2015 - 07:39 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I haven't check the service manual but around 4500 rpm I thought I read the bike goes from close loop back to open loop. (Might be 02 sensor) to lean or to rich???
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Gabby_duck
Posted on Wednesday, June 24, 2015 - 08:51 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

GENERAL The Buell DDFI operates both as an open and closed loop system which allows it to adjust for all possible operating conditions. During open loop operation, the system utilizes programmed fuel and spark maps in the ECM which provide ease of cold starting and maximum power at wide open throttle (WOT).The adaptive fuel value which is "learned" during closed loop operation is applied during open loop operation to adjust fuel and spark maps for optimum performance. During closed loop operation, the system relies on input from the O2 sensor to provide for the optimal air fuel mixture which results in reduced emissions, good fuel economy and power. In order for the system to enter closed loop operation, the following conditions must be met: O2 Sensor at operating temperature (Engine at normal operating temperature). Operation below 4000 RPM with engine under steady or light load conditions. By using both open and closed loop systems, engine performance is continuously tuned to compensate for changing conditions and provide maximum performance.
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Gabby_duck
Posted on Wednesday, June 24, 2015 - 09:01 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Above is from an 08 electrical service manual. I,m not ruling CPS or anything out.I would follow the sevice manual flow charts to properly check the mention sensors. This will save $$$ of course it dosn't hurt to have spare parts.
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Gabby_duck
Posted on Thursday, June 25, 2015 - 09:04 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

A failed O2 sensor would stay in open loop which would make the bike run a rich fuel mixture. I don't think this should shut the bike off. other blogs lean towards CPS sensor as a good place to start.
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Mcengnrng7075
Posted on Thursday, June 25, 2015 - 10:21 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thank you Allan. Wouldn't a failed O2 sensor trigger a trouble code? I don't have the manual near me but I would assume that would certainly be one of the possible trouble codes. (I don't have any codes with this issue) Believe me, I'm not trying to discount your suggestions but if an O2 sensor did fail, the bike would run in open loop mode which it would at WOT anyway. So at WOT (which lets be honest, I spend a lot of time there) I shouldn't have the problem... especially at the exact same rpm value of 4,500 every time. Furthermore, if it is true that the bike runs in open loop above 4,000 rpm, the O2 sensor (good or bad) should have no impact at 4,500 rpm. So as you said, in any case a failed O2 sensor would not shut down the bike.
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Reepicheep
Posted on Thursday, June 25, 2015 - 11:32 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The thing about the CPS check is that with a scope, a paperclip, and two allegator clips, you can pretty tell fro sure it's broken or rule it out as the problem in about 10 minutes. Take off the seat, put the paperclip through the back of the uber-deutsch connector on the ECM where the cps wire goes in, fire up the scope, and watch for missing teeth in your square wave that correspond to the explosions coming out your fuel pipe. : )

You don't even have to unplug a connector...
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Gabby_duck
Posted on Thursday, June 25, 2015 - 02:03 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

For info only I had an O2 that use to cause a hesitation at take off after about 23milea of riding.I found a chafe on the O2 signal wire I never got a code on this. I do agree with you above info though
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Mcengnrng7075
Posted on Thursday, July 02, 2015 - 10:22 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

FIXED! So, I was quite certain my issue was ignition related. I hadn't changed the spark plugs in awhile and I've never changed the wires or the coil sooo I ordered plugs, a couple wires, a coil, and a cam position sensor from Al at American Sport Bike. He and you guys pointed at the cam sensor and it seemed like the most logical cause. Today I replaced it all and I'm happy to say the bike is running great! Of course I don't know what the true cause was because I changed no less than 4 items but I really don't care, haha. I did notice that the green wire on the old cam sensor had been rubbing on the steel bracket that the noise fairing attaches to just under the cam sensor housing. The plastic jacket was compromised and its possible for that wire to have shorted to ground. But maybe that wire is a ground anyway? I don't know. Anyway, Al had pointed out that do do the static timing I need only listen for the fuel pump to prime at TDC. We are back in business, thanks for the help!
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Anonymous
Posted on Wednesday, September 21, 2016 - 11:42 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

While doing an engine swap I ran into the same problem of the engine cutting out upon hard acceleration at 4200 to 4500 RPM. Upon careful disassembly of the air box components I noticed that I'd not seated the umbrella boot inside the air box all the way down on its seating surface to the throttle body. With this not seated all the way down and upon full acceleration the umbrella boot would suck tight to the top air cleaner cover restricting air flow. Hope this helps!
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