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could someone direct me to any posts relating to how the vacuum advance unit on my '80 special works and how to determine if it's working correctly?
do these units require any maintenance? thanks
do these units require any maintenance? thanks
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A cleaning and lubing may be needed if things get dirty.Nathan
KD9ARL
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1978 XS1100E
K&N Filter
#45 pilot Jet, #137.5 Main Jet
OEM Exhaust
ATK Fork Brace
LED Dash lights
Ammeter, Oil Pressure, Oil Temp, and Volt Meters
Green Monster Coils
SS Brake Lines
Vision 550 Auto Tensioner
In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.
Theodore Roosevelt -
Look in the service manual, the procedure for testing the vac advance is in thereFormer owner, but I have NO PARTS LEFT!
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I read mechanical advance, but you said vacuum. Disregard...Nathan
KD9ARL
μολὼν λαβέ
1978 XS1100E
K&N Filter
#45 pilot Jet, #137.5 Main Jet
OEM Exhaust
ATK Fork Brace
LED Dash lights
Ammeter, Oil Pressure, Oil Temp, and Volt Meters
Green Monster Coils
SS Brake Lines
Vision 550 Auto Tensioner
In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.
Theodore RooseveltComment
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......doing that, you'll remember better at a later date.Originally posted by DAVINCI View Post81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.Comment
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Alot of it can be done visually.
Remove the timing cover on the left side of the motor. and disconnect the vacuum line from the #2 carburetor (not the #2 boot, the carb). Apply 5 inches of vacuum and see if the diaphragm fully retracts and holds. If it does then the dashpot is good. You can actually just suck on the tube if you don't have a vacuum pump with a gauge.
The vacuum advance works with, but differently than the centrifugal advance. The centrifugal advances the timing up to a point as the RPM's increase. The vacuum advance works from a metered signal from the #2 carb. There should be no vacuum at idle, a vacuum signal beginning around 2,500 RPM +/- (which will advance the timing)and then no signal again at near wide open throttle (which will retard the timing for acceleration). if you connect a vacuum gauge to the nipple on the #2 carb and work the throttle slowly you should see the vacuum collect and then disappear on the gauge.
You can watch the arm from the dashpot and at idle the dashpot should be extended fully. Give it a bit of throttle (say up to about 4000) and the dashpot should fully retract. If the parts on the timing plate are moving then the system is working.
Another way to check is to put a timing light on the #1 plug wire and disconnect the vacuum tube from the dashpot and plug the end. Run the RPMs up to around 5,000 and the timing mark should be at 31 degrees for a special (this is the centrifugal advance only). Then connect the vacuum line to the dashpot and the timing mark should advance up to around 52 degrees.Mike Giroir
79 XS-1100 Special
Once you un-can a can of worms, the only way to re-can them is with a bigger can.Comment
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avcuum advance
thanks for the explanation. turns out my system is working just as you described. must the centrifugal advance parts be lubed as a matter or regular maintenance if they are working correctly?Comment
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