'68 r50/2 rotational noise

[baddean]

Well, there is a ball cage with seven balls that runs under what's called the thrust piece that pushes in on the release rod (thrust rod) when you pull in the clutch lever.
I suppose that the ball cage could be worn and might cause your noise.
Pulling in the clutch lever could, while putting pressure on it, lessen the noise.
Actually, releasing the rod lets the ball cage run freely and that may be when you get the noise.
Also, the end of the thrust rod could be worn where it contacts the pressure plate causing a whining noise as well.
I only mentioned the generator brushes because if worn down far enough they can whine against the generator armature
but you've ruled that out.
I don't think you can pull the thrust rod out far enough to remove it while the transmission is in the bike. That rod is quite long (runs all of the way through the trans) and will probably hit the rear fender before it is completely out.
To be honest, replacing the rod with the felt on it will be hard enough with the trans out let alone with it in place.
Probably be easier to pull the trans so you can get to it easily if you are pretty sure that is the cause of the noise.
My only experience with the rod was when I had the trans out of the bike.
Dean

[312Icarus]

Think I found it...

I think I found it. With some more stethoscope work, I'm pretty sure it is coming from the clutch/release bearing/rod assy. Now I am looking to see if I can replace the bearing assy without pulling the tranny as a start. If push comes to shove, after I do that, I'll consider pulling the tranny and while I'm at it, replace the disc and the rod. 55k miles, it is probably due any way, although the disc was pretty good a year ago when I did the slinger service, so I didn't do it then.

Has anybody done the release bearing in place? Hints?

Thanks one and all,

Icarus

[312Icarus]

I think I may be back to square 1! The release bearing does make noise, a little lube quiets it, but I'm still getting the other noise! It sounds like a bell at higher RPMs, sort of a ringing. Still stumped!

Icarus

[stagewex]

I'm also thinking generator though you say it is not. We are watching from a video so kinda guessing. But sounds like from the top.
On my Ural sidecar rig if the alternator cush-drive need a dab of grease it makes a similar whine.
Grease it and it goes away.

[johnpst]

Aloha,

Because of physics, the sound is going to bounce all over the place. What you think is the location may just be the reverberation off of a resonant part of the engine. Sorry but, physics are laws not suggestions. None of us has X-ray vision so, all we can do is send good wishes and educated guesses your way.

1. Push back and forth on the flywheel. See if the crankshaft is moving or the flywheel is loose. It's possible the flywheel is rubbing on the engine case.
2. Do the same with the cam shaft. It runs at half the speed of the crankshaft so, the frequency of any noise it make will not be the same as a crankshaft noise.
3. Ping on different parts of the engine with a small, hard faced object. Needs to be hard so that it rings but not steel or anything which could damage the engine parts. See if anything sounds like the pitch of the sound when it's running. Everything in there will have an individual resonant frequency.
4. Drain the oil through clean cheese cloth. Make sure you're not shaving metal in there. If you are, it will tell you a lot about where the noise may be coming from. Bearing race shrapnel, aluminum dust, iron chips...
5. Find an NDE inspector in your area who can do vibration analysis. It shouldn't take more than an hour of their time. They can listen to your engine using some pretty high tech stuff, run it through an FFT filter and tell you if it's any of your bearings. You will need to tell them the type of bearings so they know how many balls are in them. I don't know how much they would charge but, why not use technology.

Call Vech. He'll be glad to talk to you about it and give you some ideas.

After 40+ years of engineering, the one thing I've found is, after asking, you gotta go look. I've got mine apart right now so, if you're wondering what anything looks like I can share photos.

I wish you luck. We're all root'n for ya.

John

[312Icarus]

John,

Thanks for the great ideas. (I did send Vech the videos and his response was, "I don't have x-ray vision and if I did I would be watching women. If you got a new sound, tear it down!" (Easy for him to say!)

I am going to have an oil analysis done, maybe that will reveal something. I will keep looking, until I have to give up and tear it down. I'm leaving for several months at the end of next week, so any progress is likely to be slow between now and the fall.

Once again, thanks all for the great ideas. I was hoping someone had heard it before and could give me a clue where to start looking. It is the "ringing" that is sort of mysterious. As you say, what ever noise will resonate through out the case.

Icarus

[312Icarus]

Here is the post with the rotational noise video, for those that are reading the other thread.

Icarus

[johnpst]

Physics,

A sound is brought about by movement. We all know that the engine has moving parts so, that narrows it down to those parts that move so, let's eliminate things that dont move right off the bat. So, the things that do move are supposed to move, right. You are questioning the sound so, the obvious answer is, something that is supposed to move is not moving the same way that it did before. Right? That can mean only a couple of things.

1. The movement of something that is supposed to move has changed its movement.
2. The movement of something that is supposed to move relative to something that is not supposed to move has changed.

Let's experiment with the part that are supposed to move and see which is true. The things you will need:

a. A dial indicator. It would be best to have both a linear stroke and a test gauge but, either will do the job.
b. A stiff "something" that will not damage the aluminum but be able to fit into the timing hole and shove the flywheel back and forth. It should serve the secondary function of prying the camshaft away from the crankshaft.
c. Feeler gauges, tapered end is preferable and almost necessary.
d. A 2" funnel with hose to attach to the small end. Now, to get really Rube Goldberg, if you could have a set of earmuff hearing protection that you are willing to drill holes in, a wye connector for the hose you might really have a cool tool.
e. Your iPod/phone app for finding odd sounds, I mean music.
f. 6-pack of your favorite beverage.
g. 4 quality hours.

1. Crank shaft axial movement. Remove the timing cover. Place the dial indicator on the crankshaft (generator retaining bolt). Be sure the dial indicator is not at an angle. It must be in line with the movement (less math this way). Using the tool I mentioned before, shove the crankshaft back and forth until you get a repeatable and consistent number. Write it down.
2. Crankshaft radial movement. There is way too much stuff between the bearing and the end cover for this to be a completely accurate reading but, it will give you a number you can use in future experiments and a relative movement to use now. Place the dial indicator radially on the crankshaft (generator end bolt). Vertical alignment will take advantage of gravity making this easier. Using whatever means you have available without damaging the generator, move the crankshaft nose up and down until you get a repeatable and consistent number. Write it down
3. Timing gear clearance. Mount the dial indicator so that you can get a good measurement of the timing advance plate. You will be measuring rotational clearance in about the 0.010" range. Make sure the indicator is directly in line with that rotation, the best you can. Put the bike in 1st gear and mash down on the brake pedal. You may need an assistant or just adjust the brake actuator rod as tight as you can and wedge something on the pedal. You have to prevent the crankshaft from moving. You are not going to put a lot of force on it but, you still should be sure it's not moving. Now, using an hex key in the advance hold down bolt, move it back and forth. You do not need a lot of force, certainly nothing close to what it would take to loosen it but, you will have to overcome some friction of the seals. Move it back and forth until you get a consistent and repeatable number. Repeat this at 90 degree increments four times. Add the numbers together and divide them by 4. This will give you the average clearance around the gears.
4. Drill holes in the earmuffs just smaller than the hose you bought for the funnel. If you can get a wye connector for the the hoses, you will have stereo. Connect the hoses to the funnel and you now have a serious stethoscope with a pretty focusable pickup. Caution, sound bounces off of anything with a resonance so, the sound could just be a echo being generated from another area. If it doesn't work for a stethoscope, you can mount cup holder on it and put your beer in it. My grand-kids get a kick out of mine.
5. Optional, get your parts together to remove the timing cover and study up on how to do it. Not that hard. But requires skill, not brute force. Measure all the clearances directly that I mentioned above. You will be able to take all of the measurements above and compare them to the OEM recommendations directly, except for bearing clearances on the crank and camshaft. You will be able to inspect the breather, though as Vech said, it won't tell you if you have a rear main seal leak but, you can assess it's condition.

Now, for the rule it out stuff. I can't do this over e-mail. I can only tell you what's happening and you will have to decide if that's what you are hearing.

The camshaft moves at exactly 1/2 the speed of the crankshaft. Is the sound accelerating with the same frequency as the crankshaft? I've never used an iPhone app for these thing but, SPLnFFT Noise Meter, may be able to be used to isolate the frequencies allow you you to discern the crankshaft from the camshaft. Once you isolate the frequency, you can do some arithmetic and see if some of the louder frequencies have a harmonic or dissonant relationship to each other. Dissonant frequencies will most likely be a resonant frequency of a part that doesn't move so, you can rule them out. Harmonic or 1x, 2x, 3x, etc. frequencies can be measured for amplitude and give you an idea of where the part is. To tell you what the part is, you will have to, as stated earlier, know the number of balls in each bearing, teeth on the timing and oil pump gears. You can do that math on what is called vane pass frequency and see if the frequency is a multiple of each of these components.

a. Loose slingers will be 1x crankshaft frequency.
b. Loose more rubbing flywheel will be 1x.
c. Timing gears will be crankshaft frequency times number of teeth on the gear.
d. Bearings will be 1x divided by number of balls. For the camshaft, 1/2 crankshaft speed.

Go to a real paint supplier and get real cheese cloth. Drain your oil through it. Look for shiny steel, gray mud, dull blue shrapnel, and copper/bronze colored stuff. This will tell you immediately where the problem is if you find something.

Get a magnetic drain plug. If there is a metal on metal and it's steel, this will at least slow down the possibility of it getting picked up in the oil pump.

Remove the pan. It's easy. Get some good reading glasses and a better flashlight. Look for anything in the pan that might indicate rubbing. You will not be able to see through the foam screen very well but, you may be able to see something that tells you more.

If you have and NDE company around, they could do a lot of testing to narrow down where the sound is coming from. Using your parts manual, get the type of bearings in the crankshaft. You will need to know the number of balls in each of them. If I remember correctly, there are only three types of bearing so, that will be pretty easy. You will also need to know the number of teeth in the camshaft and oil pump timing train. Mine are buried right now but, I will pull them out over the weekend and count them.

Using ultrasound, an NDE inspector will be able to discern the pulsations of the pistons, the clickity-clack of the valve train, the gear mesh of the timing gears, and the vane-pass of the bearings. From there, they will be able to discern the bad actor. They can also listen for leaks, like the rear seal but, it's pretty deep in there. It will take a pretty experienced technician but, it is possible.

In the end, it really will be easier just to take it apart. Same qty of beverage and music required. More hammering on things, which is and advantage.

Hope this helps.

You know I have a live sitting typing this on a Friday evening.

Good luck. We're all root'n for ya.

John