pickup's vacuum line

[Eddie Gravy]

do the pick up's for the coils suppose to 1/4 turn and chatter while the crankshaft spins?

i had hooked up the vacuum line to the carb boot and it chatter something awful. so much i thought it was my cams or a piston knocking. i hook it up to the instructed carb #2 and they dont move at all.

are the pickups suppose to rock or stay in one place? and confirming what i've been told the vacuum from the pickups goes on the carb body and the vacuum for the gas octopus goes on the same carb boot

[dbeardslee]

They're supposed to stay firmly mounted to the ATU plate, but the entire assembly will move as the vacuum advances. There is also a gap that needs to be set between the rotor and the pickup coils. Stock gap is .7mm, but setting them slightly closer may work better. I've got mine set at .56mm, which works well. If they're chattering you might want to insure they aren't making actual contact with the rotor.

[Eddie Gravy]

the plate chatters, should it always turn?
hooking it up what i was told to be the right way it doesnt move.

[XSokieSPECIAL]

the plate chatters, should it always turn?
hooking it up what i was told to be the right way it doesnt move.

When it's hooked to the CARB itself like it's supposed to be. I should only move when you open the throttle.

[79XS11F]

the plate chatters, should it always turn?
hooking it up what i was told to be the right way it doesnt move.

If it is bouncing back and forth all the time then it is likely that you have the hose hooked up to the vacuum nipple on the carb mounting boot. It should be hooked up to the carb. There should be a brass tube on the front left hand side of carb # 2 to receive that hose. As stated it will only move when additional throttle is added. There are specs as to when and how much it should move. Check your manual.
Rob

[CatatonicBug]

and confirming what i've been told the vacuum from the pickups goes on the carb body and the vacuum for the gas octopus goes on the same carb boot

Here's a picture of what it would look like. The hose from the pickup attaches to the carb body, and the fuel vacuum attatches to the vacuum connection closest to the engine (rubber caps should be on the same connectors for all 3 other carbs).

[oldyam80sg]

Don't hook it up wrong.If you do you will never quiet the noise and movement.

[wingnut]

The vacuum port on the carb body has a snubber or smaller orifice in it to dampen those back and forth movements you saw when it was hooked up to the carb boot. With the motor running and the cover off you should see the plate rotate with changes in throttle

[XSokieSPECIAL]

The vacuum port on the carb body has a snubber or smaller orifice in it to dampen those back and forth movements you saw when it was hooked up to the carb boot. With the motor running and the cover off you should see the plate rotate with changes in throttle

Actually it is what is called "ported vacume". The oraface in the carb bore is behind the butterfly valve (air box side) so that there is NO vacume until the butterfly(throttle) is opened slightly.

So, at idle the vacume advance machanism should NOT move. It should start moving as the throttle is opened. If it doesn't move when hooked to the #2 carb port it's possible the port is plugged, or you just have a bad diaphragm. I had to replace mine when I got my bike.

Just disconnect the hose from the engine end and suck on the hose and see if the advance mechanism moves. If it does then see if it will hold vacume.

[randy]

Actually it is what is called "ported vacume". The oraface in the carb bore is behind the butterfly valve (air box side) so that there is NO vacume until the butterfly(throttle) is opened slightly.

Well, actually, ACTUALLY, it is 'ported vacuum', but it's FULL vacuum at idle. When the butterfly opens, LESS vacuum is applied to the advance mechanism. The spring in the vacuum pot then rotates the baseplate to retard. Watch it in action, start the bike and you'll see the advance mechanism pull in full up advanced. Crack the throttle and it will retard.

At least that's the way it's designed to work, and should, unless changes have been made

[XSokieSPECIAL]

Well, actually, ACTUALLY, it is 'ported vacuum', but it's FULL vacuum at idle. When the butterfly opens, LESS vacuum is applied to the advance mechanism. The spring in the vacuum pot then rotates the baseplate to retard. Watch it in action, start the bike and you'll see the advance mechanism pull in full up advanced. Crack the throttle and it will retard.

At least that's the way it's designed to work, and should, unless changes have been made

Better check again Randy.

[randy]

All I can say is, that if yours isn't working the way I described, then it's wrong.

Better check again.

[motoman]

afraid he's right Randy. Ported vacuum, no vacuum draw at idle.

[XSokieSPECIAL]

Randy, if you have full vac at the port on the CARB at idle then you either have your idle set too high or you have an intercoursed up carb.

There should be NO vac at the CARB port at idle. If you open the throttle SLOWLY you will see the diaphragm be sucked in i.e advancing the timing.

If you open the throttle quickly the engine vac will drop until RPMs pick up and raise it again. The diaphragm will then retract AGAINST the spring ultimatley advancing the timing.

If you don't believe this, disconnect the line from the carb and with the engine running at idle apply vac to the line and listen as the RPMs increase as the timing is advanced.

[Ken Talbot]

Here's how it is written up in the January 1978 issue of Cycle Magazine:

The Eleven ignition system's second important feature, and one that's unique to motorcycles, is the vacuum-actuated advance/retard mechanism. Actually, there hasn't been an automobile produced in at least 30 years without some form of inter-connection between manifold vacuum and ignition timing, simply because spark advance otherwise has to be compromised between the conflicting demands of power and economy. Engines running under slight throttle openings have a thin, low-pressure mixture in their cylinders, and they don't run efficiently unless the fire is started long before the piston reaches top dead center. Much less ignition advance gives optimum results at large throttle openings. Yet, all motorcycles but the Eleven effectively have a fixed spark advance, with a centrifugal device to retard the timing for easy starting. And their off-idle timing has to be compromised, with enough advance to give reasonably good efficiency under cruising conditions but not so much as to cause detonation when the rider uses full throttle. The Eleven we tested had 10 degrees of static ignition advance, and another 26 degrees from the centrifugal mechanism, which adds up to the 36 degrees other engines of similar configuration have needed for maximum power. But then there's also 16 degrees built into the vacuum-advance device, and that pulls the timing around to 52 degrees BTC when the bike is cruising along at freeway speeds. Wind the throttles open, and it drops back to the power-setting; roll off throttle, and it auto-advances for economy; use some in-between throttle position, and the ignition adjusts itself to suit conditions. It's a big step out of the technological Dark Ages, and one that's long, long overdue.