Strange Rattle / Knock

[Ohio HD]

About a month ago when starting the bike after it had been sitting several days, so the motor is cold, I heard a tapping start right away. I give it some throttle, it went up and down with the RPM's, then went away. So I just chucked it to a lifter had bled down. Then a few days later, same scenario, then went away. Then it started staying around longer, and as I would ride, maybe 10 minutes or so, the sound would go away finally. But before it did, I would get a rattle sound when letting off the throttle to shift, riding easy, 2,000 to 2,100 RPM shifts.

So then lest weekend I started it cold, and heard a definite knock, kinda hard too, but before I could get down to the motor level, it stopped, and was a little ticking, then went away. Had the same exact knock on the 4th this past week, it went away again. So I put the bike on the lift so I can be near the motor to hear better, I've tried to get it to do it again, the heavy knock, and it's gone. But has been replaced by a sort of rattle, that goes to a light tapping sound as the motor warms up. Doesn't go away now, just gets quieter. Even with a stethoscope and also using a screw driver, and a hose, it's really hard to detect the location of the sound. At best, I can say it seems to be coming from the rear cylinder. Not near the head really, more prominent in the middle of the cylinder or at the base, or even the case area.

I've pulled many motors apart with a wrist pin bushing loose, but they were not making noise that I ever heard like this. The motors with a loose bushing, were quite, the loud ones, the bushing was deformed and mostly gone. I've heard rods knock, and they have a hollow knock, pretty easy to distinguish. This is a strange rattle / tapping, it almost sounds like sheet metal rattling when the throttle is let off, and more of a tapping when giving some throttle. It is most prevalent around 1,800 to 2,100 RPM.

This has me stumped as I've never heard anything like it. I know it's not the compensator or anything in the primary, as I had that all apart, and even replaced the compensator while in there a few weeks ago. The only noise coming from the primary is the whirring of the chain. I know I can pull it down and find it, but would like to determine just what it is if I can.

Looks like I may not worry about getting it tuned this year now...  unless I figure it out, and it's a quick fix. My fear is that I have cracked a piston skirt, but can't imagine it getting quieter as it warms up. If that's all it is, that's a quick fix, sort of....   

I have her on the lift with fans on the motor to cool it down, and will try to listen for it again.

This is on my 107", 4-3/8 stroke, 3.937 bore.

[05FLHTC]

Piston slap?

I had a very noisy build on my RKC was most prevalent at 2400 rpms hot or cold made little difference, never did tear it apart to confirm, traded it away

[Ohio HD]

Piston slap?

I had a very noisy build on my RKC was most prevalent at 2400 rpms hot or cold made little difference, never did tear it apart to confirm, traded it away

It's possible, but I'm assuming worse, simply because it was never there before a month ago. And it was really load a couple of times, not not so much.  It's weird.

[06roadglide]

I know you say your confident it's not the comp. but I'd check it to be certain.

[rbabos]

Does sound piston related with heat changing it's sound. Rod or wrist pin bushing wouldn't be effected like this. I've seen this before in my early days with v8s. Micro crack near the wrist pin boss. As the engine heats up the crack closes stopping the noise. Over time the cold starts beat the gap larger until even warm the knock but at a reduced level. Just one possible cause in this case. Generally predictable in noise level and when it occurs. Your case the noise changes and unpredictable. Classic test back the was to pull each plug wire off until the knocking stopped to find the culprit. May or may not work with the vtwin. Might determine front or rear. I do know you need to be around the 2k mark trying this or the comp will knock like crazy at lower rpms.
Ron

[No Cents]

Does sound piston related with heat changing it's sound. Rod or wrist pin bushing wouldn't be effected like this. I've seen this before in my early days with v8s. Micro crack near the wrist pin boss. As the engine heats up the crack closes stopping the noise. Over time the cold starts beat the gap larger until even warm the knock but at a reduced level. Just one possible cause in this case. Generally predictable in noise level and when it occurs. Your case the noise changes and unpredictable. Classic test back the was to pull each plug wire off until the knocking stopped to find the culprit. May or may not work with the vtwin. Might determine front or rear.
Ron

I would highly suggest wearing a thick pair of insulated rubber gloves if your going to try to pull a plug wire off of one of these twin cams while it's running...it will light you up in a heart beat!
just sayin

[02FYRFTR]

Sounds like piston slap to me, did bike get hot once or twice during the past.  How many miles on the 3.937" bore, forged or cast pistons, what was clearance set at when built???

[crazy joe]

Hows about cutting the oil filter open and checking for metal?
Maybe draining some of the oils and checking for metal?

[rbabos]

Does sound piston related with heat changing it's sound. Rod or wrist pin bushing wouldn't be effected like this. I've seen this before in my early days with v8s. Micro crack near the wrist pin boss. As the engine heats up the crack closes stopping the noise. Over time the cold starts beat the gap larger until even warm the knock but at a reduced level. Just one possible cause in this case. Generally predictable in noise level and when it occurs. Your case the noise changes and unpredictable. Classic test back the was to pull each plug wire off until the knocking stopped to find the culprit. May or may not work with the vtwin. Might determine front or rear.
Ron

I would highly suggest wearing a thick pair of insulated rubber gloves if your going to try to pull a plug wire off of one of these twin cams while it's running...it will light you up in a heart beat!
just sayin

Never had a problem myself, but the extra caution can't hurt.
Ron

[Ohio HD]

I know you say your confident it's not the comp. but I'd check it to be certain.

I changed the compensator for a different reason, other than noise after the motor started making this noise. I know they're not related.

[Ohio HD]

Does sound piston related with heat changing it's sound. Rod or wrist pin bushing wouldn't be effected like this. I've seen this before in my early days with v8s. Micro crack near the wrist pin boss. As the engine heats up the crack closes stopping the noise. Over time the cold starts beat the gap larger until even warm the knock but at a reduced level. Just one possible cause in this case. Generally predictable in noise level and when it occurs. Your case the noise changes and unpredictable. Classic test back the was to pull each plug wire off until the knocking stopped to find the culprit. May or may not work with the vtwin. Might determine front or rear. I do know you need to be around the 2k mark trying this or the comp will knock like crazy at lower rpms.
Ron

I can give that a try Ron, it may help identify the location. I'm pretty sure that it's a broken / fractured piston too. I just got back from a couple hour ride, so the motor is well up to temperature. I can hear the rattle a little when cruising along. If I hammer it through the gears, I only hear the exhaust...   

I suspect that I broke something, I do tend to be a little rough on em....    

[Ohio HD]

Sounds like piston slap to me, did bike get hot once or twice during the past.  How many miles on the 3.937" bore, forged or cast pistons, what was clearance set at when built???

I think that it must be noise from the piston(s). The top end has about 7,000 miles, pretty hard miles.
Bike has never been hot at all, and runs considerably cooler than my stock '09 Ultra.

Forged Wiseco pistons, front clearance was 0.0023, rear, 0.0024.

I'm pretty resolved to believing there is damage to a piston, the way it changes with temperature, and the couple times I heard hammering, then it stopped right away.

[Ohio HD]

Does sound piston related with heat changing it's sound. Rod or wrist pin bushing wouldn't be effected like this. I've seen this before in my early days with v8s. Micro crack near the wrist pin boss. As the engine heats up the crack closes stopping the noise. Over time the cold starts beat the gap larger until even warm the knock but at a reduced level. Just one possible cause in this case. Generally predictable in noise level and when it occurs. Your case the noise changes and unpredictable. Classic test back the was to pull each plug wire off until the knocking stopped to find the culprit. May or may not work with the vtwin. Might determine front or rear.
Ron

I would highly suggest wearing a thick pair of insulated rubber gloves if your going to try to pull a plug wire off of one of these twin cams while it's running...it will light you up in a heart beat!
just sayin

I'm with you there Ray, I hate getting shocked. And I've been hit with one leg of a 480 circuit before. Man I heard crackling in my ears! 

I think I need a lot bigger motor, I won't be turning the wick open quite so hard then.

[Hillside Motorcycle]

We have a client that ran his 95" HO build like a wildman.
He had us build him a 124"/HPI 62/.640/our heads/custom exhaust............he DOES NOT run that 1/3 as hard as the other combo.
Scott

[Ohio HD]

We have a client that ran his 95" HO build like a wildman.
He had us build him a 124"/HPI 62/.640/our heads/custom exhaust............he DOES NOT run that 1/3 as hard as the other combo.
Scott

No doubt Scott, no doubt.   

[sfmichael]

 

bummer dude   

[Ohio HD]

I guess I expect it to blow it's top, and that's what I don't get. I can hammer it and bounce off the rev limiter, I have it set at 6,200, and it runs fine, and strong. Maybe it's just waiting for me to get far enough away from the garage....   

[No Cents]

the bigger they are...the more you want to turn the wick up on them to have fun. Seems they just get you up there quicker...with less strain on the motor. It's nice to have it there...when you want to use it   

[koko3052]

Vegas is the place to take your chances Brian.

[Ohio HD]

the bigger they are...the more you want to turn the wick up on them to have fun. Seems they just get you up there quicker...with less strain on the motor. It's nice to have it there...when you want to use it   

I just can't believe it couldn't take a whoopen like that. I've owned Evo and Shovels with 4-3/4 stroke, and cranked the heck out of then. Never had issues like this. Of course I don't know for sure what the problem is yet, but it appears to be piston related. 

[Ohio HD]

Vegas is the place to take your chances Brian.

naaah Bill, only the house wins in Vegas.   

[BUBBIE]

 

Could a crack in the cylinder liner cause this? Thin material in a 107"

signed....BUBBIE

[Ohio HD]

Could a crack in the cylinder liner cause this? Thin material in a 107"

signed....BUBBIE

Anything is possible. But I think I would be hearing pretty good with the stethoscope in the cylinder. The sound seems to be deep inside, and almost completely goes away when the motor is warm. Got a couple of things to try when I get back to the bike at the end of the work week.

[klammer76]

Ohio,

Sorry to hear about the trouble, it's frustrating.

Klammer

[les]

Are you sure it's not lifters?  Those symptoms sound the same as what I've been struggling with on my '11 RK.  I've had three sets in there.  The start off good, then after some miles I get that chatter during cold start up.  Then the noise goes away when the engine gets hot...after 5 to 10 minutes.  Also, if I get it hot, let it set for an hour, I get chatter (again) until it gets hot.