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Strange throttle response


curlesw

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I experienced a strange throttle response this morning and hoping someone has insight into the probably cause.

 

About the bike: 05 RT, 28,000 miles, last major serve at 24,000 miles, serviced by me as required (fluids, plugs, valve adjustment, etc...), used a daily commuter, have had 10 months and put ~9,000 miles on, no problems experienced to date

 

About the incident: I was merging onto the freeway in 4th gear and needed to pass a car so I attempted to speed up. As I turned the throttle the bike initially surged but then sputtered as if out of gas (maybe a better description is it was as if I was hitting a rev limiter). This sputtering continued as long as tried to accelerate. So I slowed the acceleration and the bike continued to gain speed. I shifted to 5th and tried again, same response, also occurred in 6th gear as well. If I accelerated slowly the bike responded without any problem…I just could not “gun” it without getting this “sputtering”. I continued to work (about a 40 mile commute) and the problem eventually went away…the bike accelerates as it should in all gears.

 

Any ideas? I am thinking 1) bad gas (I filled up yesterday on the way home) or 2) a “sticky valve”…not sure what, just a thought.

 

Thanks in advance.

 

Wayne C.

Escondido, CA

 

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ShovelStrokeEd

Could be lots of things, ignition coil, fuel injector, rock in a throttle pulley, dislodged cable nipple.

 

If it doesn't come back, no harm, no foul. Usually, when there is a lag or reluctance in response to a load, I tend to blame an ignition problem, particularly the coil.

 

Bad gas doesn't just cure itself, nor does a clogged fuel filter. A fuel injector might straighten itself back out but the fuel filter should keep most of the heinous debris out of that region.

 

One other thing could involve the fuel pressure regulator. Higher and higher percentages of alcohol can lead to diaphragm failures but, again, they usually don't fix themselves.

 

Just my humble opinion.

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Wayne, how far had you been riding at the time of your problem? As Ed said it could be many things..

 

Water in the fuel would be the most logical answer as the water could have been settled in the low part of the tank but you would think it would have showed up on normal acceleration from a stand still also..

 

Might be as easy as fouled spark plug that acted up under load/RPM but returned to normal after a long high speed run..

 

I have seen vapor lock cause a similar problem but it is usually real hot & after riding for a long distance than sitting in traffic to hot soak..

 

You positive you weren’t just bouncing it off the Rev limiter? That is real easy to do when trying to beat traffic & accelerating hard..

 

I guess if it doesn’t come back just write it off as something in the fuel or a fouled spark plug.. If you get it again especially if you have run a couple of tanks or fuel through it in the mean time maybe install new spark plugs..

 

If you are really worried about the condition stop by your BMW dealer & have them check for stored codes in the fueling computer.. Maybe it trapped a faulty sensor code or other problem that stored a failure code..

 

Twisty

 

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Sounds like a fuel starvation issue to me. If it doesn't come back, probably fuel contamination. If it does I'd consider the possibility that your fuel pump may be on the way out. Usually they fail all at once but not always.

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Thanks for the responses, ideas and link...I'll check the connections and plugs. I am planning a 5 day trip next week (my first on the bike) so hopefully I can find the likely culprit or this will just "go away".

 

Wayne C.

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Wayne, how far had you been riding at the time of your problem? As Ed said it could be many things..

 

You positive you weren’t just bouncing it off the Rev limiter? That is real easy to do when trying to beat traffic & accelerating hard..

 

Twisty

 

Twisty, I had driven about 2 miles on city streets and just entering the highway. The bike was not up to operating temp just yet but very close. Also, I'm sure I wasn't close to the rev limiter, maybe 6k max.

 

Thanks.

 

Wayne C.

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Re. Strange throttle response.

Last summer I had the very same problem on my 05 1200ST.

I convinced myself it was fuel starvation. However, a BMW

mechanic advised me to 'replace the primary spark plugs'.

It sounded nuts to me but I did as directed.

Problem imediately gone! No more stuttering all summer.

 

Bud F

Ontario. R 1200 ST

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My '06 RT behaved the same way, BMW replaced the battery under warranty.

 

I first had the problem when trying to pass with the RPM's around 4500 - 5000. The bike would sputter then I'd back off on the throttle a bit and it would run fine.

 

The new battery solved the problem.

 

 

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s3steve, would the problem go away after a few minutes (10-15 min) of riding?

 

Wayne

 

At first yes then after a few rides no.

 

I made an appointment for a check up a few days after and the problem persisted until the battery was replaced under warranty. This was on a bike with less then 15,000 Kms. on it and using the BMW charger if the bike was park for more then a few days.

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I had the same prob. on my '06 rt. It turned out to be a broken ignition coil(the part that attaches to the spark plug). It cracked when the bike tipped over in my driveway. (Don't tell me you've never done it). I thought it was bad gas or fuel filter or something. By the way, does anyone know if the bike has a replacable fuel filter?

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By the way, does anyone know if the bike has a replacable fuel filter?

 

I was told it has a life time filter or "screen" in the fuel tank. Doh! Where did I hear those words before. :dopeslap:

 

 

 

Pat

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... It cracked when the bike tipped over in my driveway. (Don't tell me you've never done it)....

Just tipped it over yesterday for the first time, stupid me :dopeslap:

 

Will check the ignition coil, thanks.

 

Wayne C.

 

 

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I'd check the wires where they plug into the primary coils (this is the plug just below the plastic plug cover on the side of the valve covers). I serviced my 06RT last year and inadvertently had partially pulled the plug apart on one side. I had the exact same response you describe. After investigating I found the plug barely pulled apart. A slight push and the connector clicked together and all was good again.

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No, not yet. I got back from my trip, all went well except dropping the bike once I got home.

 

I'm still on a business trip, will get to it this weekend and report back.

 

v/r

Wayne C.

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  • 6 months later...

Just to close this out for future reference. It seems my problem was a loose plug. When I changed the spark plugs the socket was very tight on the right side but I thought I had a proper install.

 

This past weekend I bought a grinder and modified the socket (i.e. ground it down a bit so it would fit inside motorcycle without touching the side of the cylinder). I removed and cleaned all spark plugs. During this process I could tell the top right spark plug was not properly installed, it was loose. Once all the plugs were properly installed and oil changed I took it for a spin and wow…a new motorcycle! No sputtering and a noticeable improvement in throttle response as well as idling. I also noticed my mileage has improved as well.

 

So in the end it was operator error. Not sure why BMW did not make the cylinder a tad bit bigger to allow a standard spark plug socket. Regardless, I should have ensured I was using the proper tool. :dopeslap:

 

v/r

Wayne C.

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Paul In Australia

Hi

I had a similar incident, but for not as long . Turns out it was the ASC cutting in on a moss covered section of Highway. Do you have the ASC option? Not knowledgeable on Ramps in the US, but I would assume they are great places to find dropped motor fluids?

Just a thought.

best regards

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