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Weird isolated rpm vibration?

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Old Jul 25, 2009 | 11:20 PM
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Question Weird isolated rpm vibration?

On our recent 1400 mile round trip my bike developed a strang isolated vibration.
I have a 07 flhx 103 stage 1 with hd race tuner.
I also run the KW double back headers into VH basic slip ons and a heavy breather air intake.

Running up through the gears the vibration happens in every gear.
The vibration starts at 2800rpm and stops after 3100rpm.
When I got home from the trip tried it in nuetral and still does it. With the exception of when in nuetral the rear cylinder is spitting and popping up to 3100rpm.

Any thoughts?

Talked to the stealership and they said it might be a motor stabilizer out of adjustment.
 

Last edited by 88racing; Jul 25, 2009 at 11:22 PM.
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Old Jul 25, 2009 | 11:59 PM
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Did you check the motor mount condition?

The rear cyl shouldnt be spittin and popping at all. Do a CCP test on the front/rear cyl..
 
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Old Jul 26, 2009 | 01:51 AM
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Originally Posted by BAGGERDSM
Did you check the motor mount condition?

The rear cyl shouldnt be spittin and popping at all. Do a CCP test on the front/rear cyl..

Ok so how are the mounts or stablizers supposed to look like if worn or damaged?

Time to break out compression test kit? For the rear?
I will see how that goes.
 
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Old Jul 26, 2009 | 05:45 PM
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Do both so you can compare.

I had a fuel injector leak thru once, that was a wonderful adventure. And at first sent me off to the wrong direction to fix. I though the ECM had gone crazy.

I guess one could plug up just as well. That would give that cilender fits I bet.
 
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Old Jul 30, 2009 | 07:36 AM
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I don't know if I did the compression test right?
Tested each cylinder for 5 revs.
Rear started at 150 and ended up at 190.
Front started at 120 and ended up at 155.
Did the check with it being cold and slightly warm with same results.
Couuldnt find any numbers in service manual to compare to or a procedure for the hd.
 
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Old Jul 30, 2009 | 11:32 PM
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engine warm throttle wide open. Front looks weak. both should be near the same. I belive 140psi is normal and that would change with cam timming and cyl condition. but with throttle wide open. That weak front cyl you could but some oil in the front cyl and see if the Psi goes up and if it dose it looks like a cyl scuff. Weird but some times a scuff will go away with use, I would double chck my mixture and timming to make sure I am not cooking the engine at cruise speed. crank? front cams slow timming? curious minds want to know.
 
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Old Jul 31, 2009 | 06:30 AM
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Okay I will run the compression check again tonight.
Kind of a shame the bike only has 7K on it and already doing things that should happen at 25K. But with the 103 mass produced kit that I had the dealer put in the bike. I knew there would be problems sooner or later. If I can't find the problem I think its time to go bigger and get it retuned by a good shop. Let you know the results at the 2nd attempt.
 
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Old Jul 31, 2009 | 07:44 AM
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Originally Posted by 88racing
I don't know if I did the compression test right?
Tested each cylinder for 5 revs.
Rear started at 150 and ended up at 190.
Front started at 120 and ended up at 155.
Did the check with it being cold and slightly warm with same results.
Couuldnt find any numbers in service manual to compare to or a procedure for the hd.
For diagnostic purposes a leak down test will give better results. Do this with a hot engine since nobody drives around with a cold engine. It will pinpoint where the leaks are like valves, cyls. Standard compression tests are only good to determine cold cranking compression and differences between the two. Your differences are too much to have a smooth running engine. A leak down test will tell you where the problem is, with no guessing. There maybe an rpm where this roughness and mounts won't agree with each other, which is likely what you are feeling. Rubber mounts have a limited range of function to maintain smoothness.
Ron
 

Last edited by rbabos; Jul 31, 2009 at 07:52 AM.
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Old Jul 31, 2009 | 09:00 AM
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Just throwing this out there (may be a long shot), but I had a similar issue with a vibration between 2600 and 2800 rpm. Turned out to be my highway pegs. I had moved them up the engine guard a bit and they just didn't like being there in that rpm range. Since that is where I ride most of the time, the pegs got moved back down.

Just a thought if you have pegs.... FWIW.
 
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Old Jul 31, 2009 | 11:57 AM
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Originally Posted by matrix5
Just throwing this out there (may be a long shot), but I had a similar issue with a vibration between 2600 and 2800 rpm. Turned out to be my highway pegs. I had moved them up the engine guard a bit and they just didn't like being there in that rpm range. Since that is where I ride most of the time, the pegs got moved back down.

Just a thought if you have pegs.... FWIW.
I will take my pegs off and see if that makes a difference also. I had put them on for the trip and had never used them before.
 
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