mechanical advance clatter

[griennehornette]

Two steps forward, and one step back, it would appear.

Just finished re-cleaning the carbs and setting the timing. The Hornette now starts fine, and idles well. But the mechanical advance sounds like the old buzzer doorbell I remember as a kid.

I followed the manual (Clymer) carefully through the stating timing process. It was pretty frustrating; but eventually worked. Used a bent bit of clothes hanger to first keep the advance weights anchored "in" and then use the wire like a spring to push them "out" as per the manual. Well, the manual didn't really specify how to keep the weights "out" and bending the clothes wire to give a bit of pressure and hold them out seemed like a good idea...

Anyway, I've taken the weights off, greased them and put them on again. Still clatter like crazy. I'm pretty sure I did not bend the stops, as I read that's a bad move. So I'm not sure what I've messed up; but the clatter can be heard easily above the engine and exhaust.

I searched the forums, but don't see reference to this phenomenon. Or maybe my search skills leave something to be desired.

Anyhoo. If anyone has run into this before, I'd love to know. Many thanks in advance.

 

[TwoManyXS1Bs]

Can you duplicate the sound by finger fiddling with the weights and advance shaft?

Is there any sign of the rotating advancer contacting anything?

 

[MaxPete]

Hi GH: I sure would not try to bend anything in there.

I haven't checked carefully but the material appears to be some sort of light metal casting and that stuff is not very ductile and it will simply break off.

Pete

 

[griennehornette]

Can you duplicate the sound by finger fiddling with the weights and advance shaft?

Is there any sign of the rotating advancer contacting anything?

2M: First I'll need a translation. What's the rotating advancer?

I'm pretty sure that the sound involves contact. The weights are hitting something. I'll try to duplicate by hand, and see what I can hear.

 

[MaxPete]

Hi again GH:

A couple of questions:

- what happens if you run it with the cover off? Does the noise disappear?

- are there any marks on anthing? (ie. can you tell what is hitting what?)

 

[grizld1]

Pete, the tabs don't just break off. It's worse than that. They develop tiny fractures that grow as vibration plays with them, and they usually wait to drop off until you're 50 miles from nowhere. One of the worst mistakes in Joe Minton's series of articles on the XS650 was the advice to have the tabs on the timing unit adjusted at a Yamaha dealership. Not gonna happen, unless you could find a shop where nobody bothered to read--Mama Yama's instructions say not to mess with 'em, and Mama is right.

 

[retiredgentleman]

The mechanical ATU simply wears out after many years. I suspect the clearances are large, and its time to go with a Pamco and
E-advancer.
Post a picture of the fly-weights.

 

[fredintoon]

Hi hornette,
if you suspect that your auto-advance is hooped the helpful folks at MikesXS Canadian outlet will sell you a replacement.
Part #14-0652, priced @ Cdn$ 84:95
Or like the retiredgentleman sez, upgrade to electronic ignition for WAY more money.

 

[griennehornette]

Pete, the noise is there with cover on or off. Nope; can't really tell where it's hitting. Enging running, it spins to fast for me to see what's what. Engine off, I can't move them fast enough by hand to replicate the noise.

I decided to risk it, and just took it for a spin. Happily, the engine is running nicely. Not-so-happily, at any stop I keep looking around for a guy with a jackhammer. That's kinda what it sounds like. A jackhammer some distance away, mind you; not right beside me! It's not that loud. But it's loud enough to be very noticeable at stops. And I can even hear it when cruising at low revs.

Grizld, that fracture thing sounds like loads of fun! With my luck, one or both will indeed fall off 50 miles from nowhere. Something to look forward to ;-)

Retiredgentleman and Fred; to go electronic or not to go electronic. That is the question. I'll ponder. Meanwhile, I'll try to post the requested pics.

 

[robinc]

GH, I think I remember 5twins suggesting to someone to shine a timing light at it when it's running. Gives you a freeze frame view?
My memory might be wrong, but can't hurt.

 

[retiredgentleman]

Perhaps its not the ATU making the unusual noise. It could be the timing chain or the valve clearances are too large.
As a test, you could wedge some cardboard between the flyweights and the mechanical stops. That way, the flyweights cannot move as the rpm goes up. The engine will only increase rpm to a maximum of around 2500 rpm.
Start the engine and rev it up a few times to as high as it will go. If the noise is still present, then its not coming from the ATU.

 

[5twins]

I've never encountered an advance unit that "clattered", and I have dealt with quite a few of them. Usually, they're just all dried out and rusty from lack of lube. You've done part of the required advance unit servicing (lubed the pivot posts) but made no mention of doing the other part. The advance rod that passes through the cam needs to be greased too. It rotates back and forth maybe 1/8 of a turn when the advance weights fling out and come back in. This advances and retards your timing and it needs to happen easily and smoothly. With the engine off, grab that little nut on the end of the advance rod and rotate it by hand until the weights move out and contact the stops. Now let it go. The weights should snap back closed smartly. If they don't, the rod is probably all dried out and in need of a good cleaning and greasing. This is very common on these bikes today because the manuals made no mention of servicing it.

I see what looks like a plain washer under one of your weights. That wasn't original. There is a little washer under each weight but it's a very thin shim type spring washer. Also, your springs may not be the originals. All the ones I've seen are black. The springs are very important. They must have an exact certain tension for the advance to happen as it should, at the proper RPM and at the proper rate.

 

[grizld1]

Right, I've never heard a noisy ATU either--good test suggestion, RG, and +1 re. need for lube, 5T! GH, the tabs will only fail if they're tampered with. If you have excessive wear on the ATU, timing won't dial in right at full retard without advancing too far at full advance. Check it with a strobe! There are several threads on rehabilitating a worn ATU without tampering with the tabs. Search and you will find.

 

[MaxPete]

+1 on all of the above. Except for the non-standard springs and that flat washer, the ATU doesn't look too bad to me. I might also add that if the springs are non-standard - they do not look totally wrong either....

If the bike revs up beyond about 2-2500 RPM - then the springs are not likely too far off correct.

Timing chain or valve clearances?

FWIW - I will be putting a PAMCO with an e-advancer on Lucille as soon as the next installment of my allowance is given to me.

 

[MaxPete]

Sometimes you can confirm a source of mechanical noise by putting a screwdriver against a suspected source and putting the other end (i.e. - the blunt handle end) against your ear....

....unless you happen to know a medical doctor or a nurse who would loan you a stethoscope....

 

[grizld1]

Pete, a timing unit that's overadvancing due to wear will let the motor rev up just fine--until you take the bike out on the highway and hole a piston. A lot of guys have had to find that out the hard way. You can't tell much by eyeballing the tips of the weights unless your eyeball is a lot more finely calibrated than mine, but even static timing inspection will show defects. The tips of the weights need to be 4 mm. (.160") wide for best results. As little as .005" of wear will force you to fudge the idle timing to the retard side to control the advanced setting. At .008" of wear you wind up with a serious mess, and I've seen worse than that.

 

[5twins]

HF sells a cheap one. I have one and it's pretty cool. Makes me feel important when I use it too, lol. What more could you ask for 4 bucks?

https://www.harborfreight.com/mechanics-stethoscope-69913.html

From studying these advance units, I've come to the conclusion that they usually don't wear so they advance more, they wear so they retard more. The end result is the same - a greater amount of advance. There is a slash mark on the little disc that mounts on the advance rod and another on the unit's backing plate next to the circle emblem (yellow arrows). On an unworn unit, these should pretty much align. Here's mine and as you can see, they don't anymore. My unit is retarding more due to wear .....

The angle of the pic is deceiving. It's really not off as bad as it looks, but it is off. It appears that the sharp corners of the slots in the little disc are wearing into the tabs of the weights. It still times up fine. I set my idle timing near the retarded side of the range, over by the right slash mark, and that puts my full advance slightly below the full advance mark. I like the timing like this, slightly retarded. I think the bike performs and runs better at higher RPMs and speeds.

 

[griennehornette]

Day-ummm guys! How you know all this stuff?!

OK, I'll try to do all that has been sagely suggested here. Might take me a couple of days.

Grizld, I think you've convinced me to get some calipers. 0.008 might hole a piston? That makes me nervous.

And there have been enough recommendations to make me think I should pick up a timing light while I'm at it.

I gotta say, I'm kind-of amazed that my engine hasn't grenaded yet. When I first tried setting the timing, I couldn't get the mark anywhere close to the F mark. The light was going on ahead of the advance mark, even when I turned the plate as far as it would go. I noticed that when the plate screws were loose, I could get the mark closer to F; but as soon as I tightened, it backed up to the advance mark or further.

I pulled the plate off, and cleaned in behind, along with the oblong bit (points cam?) at the end of the rod. Somehow, doing that allowed me to get the light to come on at the F mark. I can't figure out how a bit of cleaning could make that sort of difference. Anyway, I wedged shut and then open the advance weights, timing first to the F mark, then the advance mark.

After that, the bike started easily and ran better; but the noise started.

Oh, and to answer your questions 5twins:
i) yes, that's not the OEM washer. I noticed one of the weights had a washer and one didn't. So I scrounged around for the thinnest washer I could find in my garage, and put it in.
ii) the springs are replacement from MikesXS (probably; I don't recall where I got them, but I have the originals, which are indeed black).

A few weeks ago, the bike was revving high after it was warmed up. One of the suggestions was cutting off one loop on the springs, and fashioning new loops to tighten the springs. This did seem to help; but now I'm wondering if I tightened them too much.

So many variables!

 

[5twins]

Yes, get a timing light. You really need one to accurately set the timing on these. The static method usually only gets you close. There are more variables with the timing plate than just it's rotation. Sometimes it has a little side to side or up and down play as well. That can throw the timing off or make it difficult to dial in.

It's usually suggested that if you're going to clip the springs to make them stiffer, only do one at a time. Sometimes just one is enough.

 

[Michaelo]

I am thinking cam chain tension for the racket.....go through the process, valve clearance, chain tension. Doesn't look like there is any wear on the ATU components to make that kind of racket.....