Return ATU (advancer) to correct range

retiredgentleman · May 14, 2011

Since I've had the bike, I realized the timing range of the ATU was too large. When set at the F for idle, the timing would go well past the fully advanced mark. This was not safe for engine longevity, so I would compromise by moving the idle timing towards the TDC mark. Not the best solution!

grizld1 had mentioned a few years back that you can adjust the advancer weights to bring it back into range by peening. I thought I need to try that, but never got around to doing it. Well, finally this spring I took the weights out and peened the little tangs on the weights. grizld1 was right as usual. :thumbsup:

I found my tangs at 0.156". At first I only peened mine to about 0.161", but the timing range was still too expanded. OK, so I removed the weights again, and I decided that the answer is to keep peening the weights until there was a very tight fit in the slot in the "slotted disk". Yamaha made the slot in the slotted disk a specific size for a reason................it gives the correct timing range of 25 degrees (15 to 40 degrees).

So, I just peened some more and did trial fits until the tang fit in the slot was a very close fit but not too tight that it would bind. It ended up at 0.168". That's a 0.012" increase in width of the tang. Your bike may be different. Just peen and trial fit until you get that "tight" fit in the slot. My timing light now revealed I had correct timing at both idle and at 4000 rpm!!

Thanks grizld1 for a great tip...................a very simple fix. :bike:

malloym · May 14, 2011

did you just hit the tangs with a hammer ?

bluebikerblan · May 14, 2011

Thanks TRG....Very helpful photo and write up of the grizld1's tip! I didn't really get it
without the photo.

malloym....Google peening, ball peen hammer, peening rivets etc. Blue

TeeCat · May 14, 2011

Great suggestion! When I re-check my timing, I'll have to look into whether I need this.

RG, I Googled this, but what tool(s) did you have at hand to do this? Punch? That's a small, delicate tang... wouldn't think it would take much to go too far.

TC

CDNTX650 · May 14, 2011

i did another fix that worked, just a small dab of JB weld on one weight so it doesn't close all the way at idle. It sure does start easier when your idle timing isn't retarded.

retiredgentleman · May 14, 2011

Peening is just a fancy word for "hitting it with a hammer'. On one side of the weight, the tang is flat with the weight, and on the other side the tang is not flat with the weight.

I just set the weight on the edge of my drill press table base (any flat solid surface should do) with the totally flat side facing up. Then just hit the tang with a hammer and it will flatten out and get wider. Keep doing a trial fit into the slot of the slotted disk until the clearance in the slot is just a few thousands of an inch. That's all there is too it................very easy.

A micrometer is useful, because it shows how much you are progressing in width as you hammer away.

PHeller · Oct 11, 2011

Link to the original thread by grizld1?

So does this stop the advance regardless of spring tension?

retiredgentleman · Oct 11, 2011

PHeller said:
Link to the original thread by grizld1?

So does this stop the advance regardless of spring tension?

The spring tension has nothing to do with the range of the advance. The fly-weights go outward until they contact the metal stops. If the tangs (ears) fit tightly in the slots of the slotted disk, the advance range will be the correct 25 degrees.

The springs allow the weights to move outward more smoothly, and aid in retracting the weights as the rpm decreases.

grizld1 · Oct 11, 2011

Thanks for the kind words, RG. The drill I follow is a little different; I grip the bobweight in a pair of well-padded locking pliers, set its base on a block of wood, smack the tip of the tang end-on with a hammer, and smooth out any rough spots with a file. But either method will git 'er done.

Some of you guys may be wondering just why you should go to the trouble of reshaping the bobweight tangs instead of just tapping or bending the retaining tabs closer. The reason is that the tabs are made of very brittle steel. The damage may be invisible, but if you try to move the tabs you'll start fractures, vibration will do its work, and when you start pulling things apart to find out why your engine suddenly quit about 50 miles from nowhere, you'll find one of the tabs lying in the bottom of the ATU cover. This isn't something that sometimes happens. It isn't something that happens most of the time and might not happen to you. It's something that will happen in less (usually much less) than 1000 miles if you monkey with the tabs. Many years ago I learned the hard way that Yamaha's warning not to mess with the tabs should be taken seriously; I took the advice of a professional mechanic (hey, he had a certificate to prove it!), tapped the tabs in ever so slightly till the advance curve was right, and wound up with my F-model DOR. I've since seen that operation done by others, and I've never seen an ATU that survived it.

PHeller · Oct 17, 2011

Can the weights be removed without removing the entire advance unit as to preserve the timing?

Posted via Mobile

5twins · Oct 17, 2011

Yes, you can just remove the weights and that's the easiest way (just pop the e-clips off the posts). However, removing the whole unit will do nothing to change or alter timing. The ATU is locked in position and located by a pin on the cam so taking it on and off doesn't change anything.

PHeller · Oct 17, 2011

Ok I tried my hand at peening the tabs, one I could barely put back into the little notch on the shaft bearing.

However, when the weights come out, they hit the tangs of the atu before the tabs on the weights affect anything.

Posted via Mobile

retiredgentleman · Oct 17, 2011

PHeller said:
Ok I tried my hand at peening the tabs, one I could barely put back into the little notch on the shaft bearing.

However, when the weights come out, they hit the tangs of the atu before the tabs on the weights affect anything.

Posted via Mobile

I don't understand what you are saying. Can you post a picture indicating where your problem is.

PHeller · Oct 18, 2011

The tabs on the outside of the atu, my weights hit them.

Basically, peening did nothing. The weights hit those tabs or stops before the peening on the weights had any effect.

PHeller · Oct 18, 2011

retiredgentleman said:
The fly-weights go outward until they contact the metal stops. If the tangs (ears) fit tightly in the slots of the slotted disk, the advance range will be the correct 25 degrees.

My tangs (ears) are quite tight in the slots of the slotted disc.

They still contact the metal stops.

Or is 25 degrees something that will only happen with inertia while the engine is running, so doing it by hand it will always contact the stops?

weekendrider · Oct 18, 2011

The outside of the weights will contact the stops in any case.
If I understand what is happening correctly by peening you have changed how far the rod will advance.
Did you happen to measure how far the disc rolled before and after?

PHeller · Oct 18, 2011

Not at all...but that makes sense. With alot of slop in the tab/slot of the disc, the disc could potentially move 30 degrees. Take away the slop and the disc can't turn more than 25 degrees. So adding material (like JB Weld) or even tape on the outside of the weight would make it contact that stop sooner in the rotation of the disc, limiting the advance as well.

In the end, I'll have to finish installing my PMA before I can see if the advance is in the correct range.

I will note that peening the weight tabs was more difficult than expected. The metal is much harder than I thought.

retiredgentleman · Oct 18, 2011

PHeller;

I think you're trying to make this into something more complicated than it is. The ATU is a very simple device. The weights are supposed to hit the stops when they fly outward due to centrifugal force. The timing range only expands due to the "slop" between the slotted disk slot and the little ears on the weights. You make the ears larger by peening until the ears are a tight fit in the slots (but not so much that they bind). That's all there is to it. You do need some mechanical ability to hammer the ears larger.

The true test is done with the timing light...............that's the only way to know if its correct.

PHeller · Oct 18, 2011

No-one mentioned previously that timing range was a result of the slop between slotted disc slot and weight tabs.

That was my confusion. Not in the actual peening of the weights.

I'm a background information person, not just a "do it this way" type of person. I wanted to know how peening the tabs actually limited the advance.

And now I know.

(insert GI-Joe slogan)

TX650A Van Islander · Oct 4, 2020

I realized yesterday that my timing was too far advanced, and read about this solution. I was so close to having the little tabs fitting just perfectly into the slots, which had nicely reduced the sloppy movement, when whack! One more blow of the hammer when the weight was just not resting on my vice/anvil properly, and it was over for that weight.
Are all weights from all years the same? I may have access to one or two locally.

Return ATU (advancer) to correct range

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