Noises - Noises

[Kool_Biker]

As some of you know, I have recently finished a nut and bolt restoration of my 79 CBX, and here's the engine part ... http://youtu.be/mznSALkbrfM
I am now at the point where the bike handles and goes very well, pulls great from low down and up to my running-in self imposed 5K RPM limit, faultlessly. Cruising is also great.
And here's my problem:
I have never ridden nor 'heard' another CBX in anger and I do not know if the various sounds I hear are normal or not.
OK, I recognise the well documented 79 clutch rattle, there is a bit there, and may be a bit of top end tic - toc which could be my original Oldham Couplers, and I am not worried about these the least.
What worries me some is a 'racket' I get when the engine is at normal operating temperature and I rev the bike starting at about 2.5K RPM and GOING AWAY at about 4K to 4.5K.
Now I use the word 'racket' for lack of a better one; It is harsh and definitely audible and, seems to be coming more from the LHS.

The bike is on normal carburation, all nicely balanced by now, Delkevic exhaust system (copy of Honda original) and everything is standard.

Any ideas ??
Cheers, Aris

[EMS]

Usually, the thing that makes noise on the left hand side is the alternator.....

[Rick Pope]

Mike is correct. In doing your restoration, you did put in new alternator bearings and seal? Even if your spring is slightly out of spec. and clutches are fair-to-poor, it should be quiet down there.

Pull the alternator and spin it by hand. If there is even the slightest notchiness or roughness to the bearings replace them immediately. You can use standard industrial bearings, 6201 and 6203 sizes. The seal is also a common size.

[Kool_Biker]

To be honest, I was thinking more in terms of my primary chain, although I did spend oodles of time making sure its tensioner was properly assembled, oil seals were in place etc, etc prior to closing the crankcases.

Can an alternator be that noisy? And can its noise come in at a certain RPM and then disappear further up the range?

In any case, I will certainly look into my alternator, ASAP, and report back. I am well aware of many forum threads re the CBX alternator.
Thanks, Aris

[EMS]

Aris: Everything is possible. Although the primary chain is located in the center, the driven shaft for everything, except the alternator, goes to the right and normally emits noise to that side. As you said, you could hear it from the LHS,it points towards alternator. But if you are suspect of the chain itself, that could be heard on the left, I guess.

[Kool_Biker]

On to the Alternator tomorrow ... and the good old game of solving a problem by eliminations begins :)

[daves79x]

Aris:
Some things to sleep on: As Rick said, very carefully check the alternator bearings for roughness and noise. Were they new at the rebuild? Were the clutches new also, or what is their condition? Any evidence of recent slippage? Oil grooves still present in the drive plate? Are both the fiber and steel shim in place? An extra steel won't hurt. Is the spring sagged? A new one measures about 31.2 MM. Last, make sure the aluminum button is still pressed into the end of the primary shaft. Make sure the small hole is open - that's the oil feed to the alternator clutches. If this button is missing, you may see low oil pressure to the primary chain tensioner and hence the noise. I believe it acts as a restrictor. I've got a bike here right now that had that problem. Replacing the button quieted the bottom end somewhat, but it has other problems.

You mentioned that you carefully installed the primary tensioner oil feed and associated rubber seals. I've seen the bottom one come loose during assembly of the cases and end up in the sump. Also an oil pressure drop to the tensioner results.

However, the alternator is your most likely source of left-side noise. I'm sure you'll keep us posted.

Dave

[Larry Zimmer]

Hi, Aris,
Does it sound like a box of rocks?! My '82 did this in the past. Additionally to all the good things Dave mentioned, you might try lapping the clutch plates together with valve lapping compound. Then, clean them good. When reassembling, cover them generously with molybdenum grease as the book says. This did a 90% fix for mine. Still makes a bit of the noise occasionally; but, nothing like what it did previously. Good luck. It's annoying as anything can be.

[Kool_Biker]

Thanks for your overwhelming responses, I hear you all.
Earlier on today I opened the alternator drive and everything you mention and that needs to be in place, is, and measures right.
Also the alternator bearings are just fine and the whole assembly is nice and smooth.

P1060837.jpg

BUT, and this is a BIG but, I think we are on to something.
The drive plate is trying to tell me something I am not sure how to read ... there is something wrong with it, so I attach a couple of close ups FYI.

P1060842.jpg

P1060844.jpg

Even if this is not the source of noise I am trying to detect, there is something there, some slippage to begin with ...
Any thoughts?
Cheers, Aris

[EMS]

Have you taken a straight edge and see whether the plate is plane or convex? From the pictures, it looks like it is concave and contact is made on the outer edge only

[Kool_Biker]

Just had a look, it most certainly is!
Now what ... :)

[Don]

I think it was Mike Nixon who reported that Honda made them that way - Some think in error. I disagree because machining a flat plate would have been 10X as easy to do as making the beautiful concave one you have there - I think Honda did that on purpose. Look at the radial lines there on either side of the oil channels on the close-up of the drive plate . . . . that is no 'accident' or 'mistake - They very much had a 'plan' in mind when they made that plate

The one concave plate kinda makes sense to me. The inner part which is not making contact will be well lubed and carry oil outward to the friction surface and that narrow contact area will slowly widen as it wears in

Some guys machine or sand the plate flat so that it makes 100% contact with the other plate - I personally think that's a mistake. If I had a beautiful, brand new pair like you have, I would just add an extra shim washer to give it just a little more pressure and let 'nature' take it's course

Don

[Kool_Biker]

But in all fairness Don,
Mike Nixon has also produced a confidential internal memo from American Honda, which sort of admits to this as a problem ...
More over, my spring is spot on 31.2 mm (new) and so are the two washers, steel and fibre.
And remember, I am not exactly racing my running in bike ..

In any case not in great hurry, still looking into this, I will get it right in the end.

Thanks a lot, Aris

[Don]

Aris,

I agree that Honda found they had a 'problem' - I don't think the clutch drive worked out at all like they planned . . . . and it *was* a pretty crazy idea to begin with. Insert a constant source of worn powdered iron into the oil supply of a close tolereance high performance engine . . . . the engineer(s) must have been CRAZY - Boy, it would have been interesting to be a fly on the wall when they were arguing about that one

In my (limited) experience, the alternator clutch on a CBX slips lots more than is necessary, especially right after you fire it up when the regulator is putting a full 12 volts on the rotor and the alternator is trying to put juice back in the battery quickly. I understand their desire to isolate the too large diameter rotor from near instant RPM changes you get when a bike like this runs up though the gears - It would probably have been a problem if they didn't isolate the alternator somehow, but having a coupling so loose that it slips like mad when under normal charging loads doesn't make too much sense either . . . . you're really going to have wear on the plates if that's the case

On my first CBX (which was a little hard to start) I could tell exactly when the clutches were slipping and when they weren't and they slipped a LOT, especially at lower RPM's and during the first 5 or 10 minutes of any run - Once the engine gets above 4,500 or so, the clutches seemed to lock up fine . . . . it was the 2500 to 3500 band where things were worst, and noisiest. I added a pretty thick, home made washer and it made things immensely better . . . . slippage was never a problem after that and I didn't experience any unusual bearing wear either. So long as you don't go so thick that you coil bind the spring, I don't think the extra pressure will hurt anything . . . . and anything which does away with 90% of your slippage has got to be a big help IMO

I think it will definitely slip less if you flatten that concave clutch plate though, largely because the friction surfaces won't be getting as much oil. There are multiple ways to go here . . . . It will be interesting to follow your experience with this . . . . we can probably all learn something new

Don

[Kool_Biker]

Don

By 'powered iron' above you really mean 'powdered iron', right?

Interestingly, I have experienced this, as a bit of 'oily dirt' gathering just below where the two plates rub, and believe me, did not like it at all!
It wasn't a lot, but stupidly wiped it off, before I could take a pic.

But surely parts of this would find themselves deep into the crankcase, and then hopefully be caught by my magnetic sump plug.
Indeed, as experienced during my last oil change, this has collected some ferrous stuff, although not sure from where, in what is a recently rebuilt engine.

P1060008.jpg

Aris