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Knocking sound at very specific RPM

11K views 92 replies 18 participants last post by  slickvic 
#1 ·
I’ve just noticed an oddity with my ‘09 Kingpin and it’s somewhat worrisome. The engine will develop a knocking sound at a very specific RPM. I don’t know what RPM it is because I don’t have a tach, but its most noticeable at 64 MPH in 6th gear. The sound disappears just below that speed and just above it. The knock gets louder with load. If I just feather the throttle, it’s not noticeable, but as I twist the grip (say, going up a hill) it gets quite loud. It does this in every gear, but it’s most noticeable at higher speeds in 5 and 6 due to the load.

Temperature plays no part in the noise. It makes the knock just as loudly at mile 1 as it does at mile 100.

Lastly, this bike was hardly ridden until I bought it in late summer. When I got it at the end of August, it had 8,000 miles on it and now sports just over 11,000. The bike runs awesome and I am enjoying the hell out of it, but this knocking is concerning.

Any ideas?
 
#2 ·
I think this would be normal if you are lugging the tranny. At 65mph in 6th gear, I'm thinking you're running around 1500-1800 rpm. If you have the stock speedo, does it not rotate through the modes to show digital display of RPM? If so, try riding and keep the RPMs over 2000rpm (and shift around 3000rpm), I think you won't have this happen any longer. Think of 6th as overdrive, downshift to accelerate.
 
#3 ·
Could it be detonation? What octane are you running? Have you pulled the plugs and checked them? Could be running lean.

also agree with Laser….at 65mph you should be in 5th. I always run 2500 or more. Shift at 3200-3500 as normal riding. For fun, I run her up to 4500 or more.
 
#6 ·
I always put 93 octane gas in the bike. The sound is more of a rod knock sound than a detonation sound. In fact, it sounds quite a bit like a bad rod bearing, but comes and goes.

As for lugging the motor, I agree than 65 is a little low for top gear, but if it was lugging, I would expect it to continue to make the noise at lower speeds (below 65), but the sound goes away. Sounds like the easiest way to remedy this is to simply shift at higher RPMs.

I’ll have to check the speedo to see if it has the digital tach feature. I had no idea about this!
 
#7 ·
Maybe a pronounced valve train noise? You could try some seafoam for a short bit and see if that "unsticks" it. Maybe intermittent?

how long has it been going on? Did it just start? What was the last thing you did to the bike?

check out this video from the Vic shop

 
#88 ·
Just got mine fired up on friday with the BB kit and new cams, and I feel that I have this knockingnoise all the time on idle.
But maybe it is my rocker arms that did not like the 116 upgrade with new cams and forged valvesprings then?
I definetaly need to take off those valvecovers again tomorrow and have a look at the rocker arms!!
 
#9 ·
I wasn't sure about that. I would assume there is a tach being it's manual transmission, whether it's digital or analog I wouldn't know. Is there a mode button on the '09s?
 
#12 ·
Try using sea foam in the gas in case is a dirty fuel injector causing starving for fuel ping & also run some in the crankcase oil just in case a lil piece of trash got inside that little tiny hole in the cam chain tensioner and not letting it fully open and remove all chains slack. Good luck & let us know what happens
 
#16 ·
Wait ….. this sounds familiar. I’m betting based on what your saying you have a blown head gasket. Ask me how I know. ok I’ll tell you.
everyone that rode the bike said it was fine but didn’t ride it like I told them to. Hard throttle in either 3rd 4th or 5th gear accelerating and the knock sound appeared. How I found it ….. bike sitting running and warmed up. In neutral grab throttle and Rev to limiter and puff of oil mist coming from the head gasket front cylinder.
Hey it’s worth a check.
 
#18 ·
One of the easiest ways to find phantom noises is put it on a dyno run it loaded at the speed and rpm where the noise comes in.
No. it's not that expensive for a diagnostic run, you're not tuning the bike so all you're doing is making one pull with just the most basic settings on the dyno.
Most I've paid was one hour shop time. I've done this three times in the past 5 years chasing phantom noises. It's worked every time, one Buell that turned out to be excessive cam gear slop, it would only do it at 3k in 2nd and 3rd gear at a no load throttle position.
One 1275 kitted Sportster with a bad crank pin, same thing would only make noise at a certain speed and rpm.
One Vic with a bad piston, that was operator error not letting it warm up, same thing wouldn't make the noise unless it was running under a light load at a specific rpm.
 
#19 ·
Thanks for the great replies. FYI: the bike is totally stock, except for drilling some holes in the ends of the mufflers for some added growl. Interestingly, doing this changes the entire dynamic of how the bike sounded, so the noise (which had always been there) is more pronounced.

I do like the idea of running it on a dyno. I had never thought of that. I have a dyno shop pretty close by.

**One thing that I completely forgot about** : My wife reminded me that last October we were on a 3-day ride and the bike did something weird on the last morning. It was warming up while we were putting our gear on. While it was idling, this same knock sound slowly got louder, then faded away. It did this twice - each time fading in, then fading out. That was the one and only time it’s ever done that. It was one of those “what the hell was that?” moments. Could it be related? I don’t know. Thanks to my lovely wife for the reminder (along with the reminder to take out the trash).
 
#20 ·
I've just noticed an oddity with my '09 Kingpin and it's somewhat worrisome. The engine will develop a knocking sound at a very specific RPM. I don't know what RPM it is because I don't have a tach, but its most noticeable at 64 MPH in 6th gear. The sound disappears just below that speed and just above it. The knock gets louder with load. If I just feather the throttle, it's not noticeable, but as I twist the grip (say, going up a hill) it gets quite loud. It does this in every gear, but it's most noticeable at higher speeds in 5 and 6 due to the load.

Temperature plays no part in the noise. It makes the knock just as loudly at mile 1 as it does at mile 100.

Lastly, this bike was hardly ridden until I bought it in late summer. When I got it at the end of August, it had 8,000 miles on it and now sports just over 11,000. The bike runs awesome and I am enjoying the hell out of it, but this knocking is concerning.

Any ideas?
 
#21 ·
I've just noticed an oddity with my '09 Kingpin and it's somewhat worrisome. The engine will develop a knocking sound at a very specific RPM. I don't know what RPM it is because I don't have a tach, but its most noticeable at 64 MPH in 6th gear. The sound disappears just below that speed and just above it. The knock gets louder with load. If I just feather the throttle, it's not noticeable, but as I twist the grip (say, going up a hill) it gets quite loud. It does this in every gear, but it's most noticeable at higher speeds in 5 and 6 due to the load.

Temperature plays no part in the noise. It makes the knock just as loudly at mile 1 as it does at mile 100.

Lastly, this bike was hardly ridden until I bought it in late summer. When I got it at the end of August, it had 8,000 miles on it and now sports just over 11,000. The bike runs awesome and I am enjoying the hell out of it, but this knocking is concerning.

Any ideas?
I had an odd ticking more than knocking at 2300. It ended up being a rocker.. 2011 XC
 
#25 ·
Related to your earlier experience with the bike. I have heard it said and have had a very small experience with the bike warming up on the stand and acting slightly "oil starved". Get a tic, might be loud or not so much depending on a number of circumstances. If the oil is a little low to start with. Anyway, that might have happened to you and there could be some carry over damage trying to manifest. I don't warm my bike on the stand anymore.
 
#26 ·
@.John sounds like it could be piston slap, run good oil in it, start it standing straight up, let it warm up a few minutes before riding and don't beat it until its been running a couple miles. Then start riding it harder and wind it out to 4k to 4.5k a bunch of times. This helps keep the valve train noises in check.......And change oil every 3k, the oil gets beat up in these motors.....:bandit:
 
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#27 ·
Thanks for the great replies. FYI: the bike is totally stock, except for drilling some holes in the ends of the mufflers for some added growl. Interestingly, doing this changes the entire dynamic of how the bike sounded, so the noise (which had always been there) is more pronounced.

I do like the idea of running it on a dyno. I had never thought of that. I have a dyno shop pretty close by.

**One thing that I completely forgot about** : My wife reminded me that last October we were on a 3-day ride and the bike did something weird on the last morning. It was warming up while we were putting our gear on. While it was idling, this same knock sound slowly got louder, then faded away. It did this twice - each time fading in, then fading out. That was the one and only time it's ever done that. It was one of those "what the hell was that?" moments. Could it be related? I don't know. Thanks to my lovely wife for the reminder (along with the reminder to take out the trash).
Just re- read this post, could it be a loose baffle? I hadn't really noticed the part about drilling the pipes. Could have come straight from the factory with something inside a muffler or loose baffle.
 
#28 ·
Or loose head pipes snug up the exhaust nuts
 
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#35 ·
So, a little update on the bike: I performed a compression check (cold) and the numbers looked pretty good . . . rear cylinder: 195psi, front cylinder 190psi.

The plugs looked good - maybe a little on the lean side, but that's probably part of the stock tune to meet EPA mandates.

I have also ordered a borescope so I can inspect the cylinder walls.

On Tuesday, I took it for a ride (60 degrees here in TN) and found that if I just keep the revs slightly above where I had them, the noise is all but gone. I'm starting to wonder if this issue isnt self-inflicted.

I'll post some pictures once the borescope arrives.
 
#36 ·
. . rear cylinder: 195psi, front cylinder 190psi.
I want the ability to see inside my cylinders as much as everybody else but with those numbers I bet their good. At worst, maybe lil extra carbon build up on top of pistons and the valves but lil sea foam through gas tank would help clean that up. Being a wet clutch I'm not sure about adding to oil. Clean, regap plugs and keep those rpm's above at least 2000, between extra valve noise going away, much less chance of tranny lash or tip in, your fuel economy increasing and the bigger smile on your face, it'll improve the feel of the bike. Vics truly were engineered to rev
 
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#42 ·
So, I finally got a chance to try out the new borescope. Here are some pics:

The first 5 pictures are the FRONT cylinder, while the last 3 pictures are the REAR cylinder.

Thoughts?

View attachment 592537 View attachment 592539 View attachment 592541 View attachment 592543 View attachment 592545 View attachment 592547 View attachment 592549 View attachment 592551
3rd and 5th picture show some scoring, you may have wiped a piston. On one of Rylan's videos he's got some bad pistons sitting on his bench. I believe it was the video about big bore kits, steel vs nikasil cylinders. Compression numbers aren't that bad . Manual says 185lbs. is within acceptable limits. 210 to 225 are the ideal numbers according to the manual.That's for the 106, don't know how much difference there might be between the '08 and '09100 inch motors.
The big problem with carbon buildup is on the valves more than on your piston.
 
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