Topic: Is this spark advancer bogus? (With Video!)

[BigBoi]

Hey all,

I'm trying to work through my fouling plugs issue (http://forums.sohc4.net/index.php?topic=69312.25), but I've come across a timing issue which may or may not be related.

I bought a timing strobe light today after I statically timed my new Dyna S unit. I hooked up the strobe to my bike and it appears my timing is out by at least half an inch to the right of the "F" mark. This is the case for both the 1-4 and the 2-3. I pulled off the advancer unit because I suspect it's sticking open. I cleaned it up really well, added some oil, and put it back in but it seems to not snap back in place. It stays open maybe a quarter inch. Have a look:

I'm wondering at this point if there's a fix for this. I've seen Hondaman threads about cutting a loop off and bending a new one, but I thought it may just be for the 550. My bike is a 72 750K. Stock everything except 4-1 exhaust from an F model.

So can I cut a hoop off or do I have to replace the unit?

Thanks!

[Gordon]

With the Dyna-S, ignition timing is supposed to be set at the full advance mark, not at the "F" mark at idle.   When set correctly and checking the timing at idle with a strobe, it will be off some like you described.

[750goes]

take the advancer off and clean it up with some fine emery paper and lubricate it - it should snap back into spot, if it hangs up it is not working properly.. or you could have weak springs on the advancer unit??

[chickenman_26]

Hey all,

I'm wondering at this point if there's a fix for this. I've seen Hondaman threads about cutting a loop off and bending a new one, but I thought it may just be for the 550. My bike is a 72 750K. Stock everything except 4-1 exhaust from an F model.

So can I cut a hoop off or do I have to replace the unit?

Thanks!

It doesn't take much stretching of the springs before this problem comes up. It causes the timing at idle to be way off as you see. The plugs may foul, and the idle will be lousy due to the timing jumping around. It usually doesn't take much to tighten up the springs. Remove about 1/3 of the loop that's hooked to the weight. Then bend the remainder back into shape. That should cure it.

Stu

[BigBoi]

It doesn't take much stretching of the springs before this problem comes up. It causes the timing at idle to be way off as you see. The plugs may foul, and the idle will be lousy due to the timing jumping around. It usually doesn't take much to tighten up the springs. Remove about 1/3 of the loop that's hooked to the weight. Then bend the remainder back into shape. That should cure it.

Stu

This is what I thought Stu. I had taken off the advancer and cleaned it up well, oiled it. Still won't snap back. I'll cut off a little coil and hopefully she'll snap back snug.

Gordon: I totally timed my Dyna S unit the wrong way. I did time it on the F mark without touching the rotor. Maybe I should learn to read instructions.

[mystic_1]

Has the advancer always been like this?  If so you should have noticed some issues when running the points.

I'm not convinced that you springs are the problem, based on the video.  Before you hack into them, take them off and examine the rest of the advancer to make sure it operates smoothly.

Did you disassemble the advancer when you installed the Dyna?  Any possibility it's assembled wrong?  It's possible to put the cam on 180 degrees out, and I think it's also possible to improperly engage the fingers at the base of the cam with the matching fingers on the advancer weights.

Got closeup pics of the advancer?

mystic_1

[MCRider]

I agree with Mystic. What I see is a mechanical hangup, burr or sticky spot. THe cam should snap back even with fatigued springs, when its not otherwise spinning.

When its spinning the fatigued spring can't overcome the centrifugal (sp?) force. But when stationary, it should snap back.

Or so I think.

[BigBoi]

Has the advancer always been like this?  If so you should have noticed some issues when running the points.

I'm not convinced that you springs are the problem, based on the video.  Before you hack into them, take them off and examine the rest of the advancer to make sure it operates smoothly.

Did you disassemble the advancer when you installed the Dyna?  Any possibility it's assembled wrong?  It's possible to put the cam on 180 degrees out, and I think it's also possible to improperly engage the fingers at the base of the cam with the matching fingers on the advancer weights.

Got closeup pics of the advancer?

mystic_1

This bike is new to me and was sitting for a while before I completely rebuilt it (minus the engine). So it's not really possible for me to tell if it was always this way.

When I installed the Dyna S unit, I took the advancer unit out, removed the center tube, added some oil to the shaft and put the Dyna black magnet tube (cam?) on as per the directions. Magnet showing left when 1-4 is at the top. I also removed that little pin as directed.

The bike did run alright with the Dyna unit in, but still fouls plugs. So I'm trying to eliminate some things, starting with the timing which is not right.

I took apart the advancer last night when I noticed that it doesn't snap back in place against the black tube (cam?). I made sure I put everything back the way I took it off. I cleaned the advancer with a wire brush, added some lube to things that pivot and put it back on the bike. The video you see is the result. It certainly does not snap back into place.

Before I go ahead and cut the springs, I'll make sure there's nothing preventing anything from turning.

[BigBoi]

I agree with Mystic. What I see is a mechanical hangup, burr or sticky spot. THe cam should snap back even with fatigued springs, when its not otherwise spinning.

When its spinning the fatigued spring can't overcome the centrifugal (sp?) force. But when stationary, it should snap back.

Or so I think.

Just out of curiousity, my advancer has 3 small washers at the bottom end of the cam. I say washers but they're paper thin. Did you guys remove them when going to the Dyna S?

[mystic_1]

Hmm, watching the video a bit more closely, what it looks like is that towards the end, you're turning the cam so that the weights "close" all the way (0 advance) but as soon as you let go, it springs back open (partial advance).  Am I seeing this correctly?

mystic_1

[BigBoi]

Hmm, watching the video a bit more closely, what it looks like is that towards the end, you're turning the cam so that the weights "close" all the way (0 advance) but as soon as you let go, it springs back open (partial advance).  Am I seeing this correctly?

mystic_1

Yes. I'm sorry the video wasn't more clear. Right near the end, I turn it closed a couple times to show the amount of movement, but when I let go, it doesn't snap back.

Any input on this "special washer" that sits at the bottom of the cam? There's 3 of them and they seem to have a cutout for the pin maybe? They're literally thiner than paper...

[BigBoi]

Came across this if anyone is interested:

http://forums.sohc4.net/index.php?topic=63020.0

Last post shows the spacer I'm talking about and that it isn't necessary.

[mystic_1]

OK good to know I WAS seeing it wrong.  I watched the video yet again and I see that it's not springing back open to partial advance on it's own, you are turning it with your fingers.

The washers you refer to look like shims to be, probably there to achieve a certain clearance between the cam and the advancer body.  By all means omit one or more of them and see if your issue clears up.  What sort of lube did you use?  Should use a light oil, no grease.

If you take the springs off and turn the action by hand, how does it feel?

mystic_1

[chickenman_26]

Has the advancer always been like this?  If so you should have noticed some issues when running the points.


mystic_1

Mystic,
I thought the same thing, so I reinstalled the points temporarily to see why that was.
When the points are installed, one of the rubbing blocks is always in contact with the cam. And that provides enough drag on the cam to keep the cam in full retard at low rpm. With the Dyna S rotor installed, there's no drag at all, and nothing to prevent the rotor from floating around if the springs aren't holding the weights tight.

Stu

[BigBoi]

Went throught the exercise last night. Pulled it out, removed the spacers, oiled it all up, but it still didn't snap.

Removed a little of the spring (maybe 3 mm), and curled it back onto it. Now it snaps back well.

Put it back together, timed it as per the instructions to the advance mark with the rotor turned. Checked it with a timing light and it seems to be bang on when I rev the engine around 2700-2800 rpm on the advance mark. At idle, the strobe shows the mark being around here:

          |
  T|    F |

Is this acceptable at idle? Unfortunetly, I didn't get a chance to ride the bike due to rain.

One more thing I'm wondering about. I read somewhere on the site that if I adjust the mixture screws with the bike running, I should see some drop or increase in RPM at idle. I can't seem to get it to move at all when I make adjustments. Is this possible?

[bistromath]

It is, but without a good digital tach (or a golden ear) it's difficult to tell sometimes. Generally you should be able to dial it in for a smoother idle, and the smoother the idle gets the higher it will idle (makes sense). The process for me takes probably half an hour, during which the bike has to be warmed up and a fan put in front to cool the motor while it idles. You can home in further on the best setting by lowering the idle speed with the idle speed adjustment screw, since at lower RPMs any lumpiness in the idle gets lots worse.

Oh, and make sure you vacuum sync the carbs before you do this.

[BigBoi]

                   |
  T |  F |     | |

This is how Dyna says to set full advance. Try that, and see if the F mark doesn't move closer to where it's supposed to be at idle.

Stu

I see Stu. I set it to around the middle:
                |
T |  F|     |  |

So you're saying on the outside right line should be right?

[chickenman_26]

I didn't need to do that to get the F mark spot on at idle, but those are Dyna's instructions.

While holding the rotor in the fully advanced position, the right hand advance mark should align with the fixed mark on the engine case.

You're obviously getting plenty of retard from those springs - a bit too much, actually. If you want everything spot on, you could temporarily set the idle a bit below 1000rpm to insure full retard, then advance the timing to the F mark. If the full advance doesn't go outside the lines, you're good. But if it goes too far at full advance, you could tweak the advance weight stops in very slightly to limit the advance. There should be a thrust washer above and below the weight where it fits on the pivot pin. If those washers aren't there, the weight could cock as it moves outward, and that could affect the total amount of advance.

Stu

[BigBoi]

I didn't need to do that to get the F mark spot on at idle, but those are Dyna's instructions.

While holding the rotor in the fully advanced position, the right hand advance mark should align with the fixed mark on the engine case.

You're obviously getting plenty of retard from those springs - a bit too much, actually. If you want everything spot on, you could temporarily set the idle a bit below 1000rpm to insure full retard, then advance the timing to the F mark. If the full advance doesn't go outside the lines, you're good. But if it goes too far at full advance, you could tweak the advance weight stops in very slightly to limit the advance. There should be a thrust washer above and below the weight where it fits on the pivot pin. If those washers aren't there, the weight could cock as it moves outward, and that could affect the total amount of advance.

Stu

One last question Stu...when I check the timing...is the engine supposed to be fully warmed up?

[chickenman_26]

One last question Stu...when I check the timing...is the engine supposed to be fully warmed up?

It doesn't matter. Your timing is controlled mechanically according to rpm. The engine temp has nothing to do with it.

Stu