Another Vacuum Advance / Retard problem

[MartyA]

I am going over the Mangler, and I notice the vacuum advance is not moving at all at idle. I am accustomed to seeing it bouncing a little, and when I roll on the throttle I get it to turn some. Today I get nothing. So I took it all apart.

Centrifugal advance cleaned and lightly greased.
Pickup coil plate was a little sticky, soaked and cleaned it, turns easily now.
Put all the parts back and tested the vacuum advance unit, it retracts at around 6 on my gauge - book says 5.9 inches.

I put the gauge on the hose going to the #2 carb nipple, the needle barely moves, even if I roll the throttle on and off. The hose is clear, I can blow into it and hear air moving through the manifold through the nipple.

Just for fun I moved the hose over to #1 synch nipple, that hammered the heck out of the vacuum unit. So with vacuum the unit does work.

Bike starts right up, idles fine, runs fine (probably some acceleration is suffering without the ignition vacuum), problem is with the vacuum hose hooked to #2 nipple, I got no vacuum??

Any ideas? What am I missing, besides vacuum from #2 cylinder?

[TopCatGr58]

Hey Marty,

How's the plug look in the #2 cylinder, much cleaner than the others....lean? Have you checked your intake manifold recently for new leaks? You say you can hear air going thru the carb when you blow on the hose, so you've ruled out that the port might be blocked!?

With the engine running/idling, when you pull the hose off of the #2 vacuum carb port, does the engine rpm or sound change? If not, then I would look hard for a vacuum leak? Is the #2 boot synch port also connected to a vacuum line for the petcocks? Might be a leak in that line. Try plugging the Intake boot port, or moving the petcock line to another synch port, #3 for example?
T.C.

[MartyA]

Yeah, the only thing that makes sense is the air for that cylinder is coming from a leaky boot instead of flowing through the carb, or not getting ANY air. IF the boot was leaking, the spark plug should show lean. Typically on mine #1 and #4 show a bit lighter gray/tan than #2 and #3. I did not pull the plugs last night when I discovered the problem - it was late, but Saturday morning they were fine, looked just like they always do.

If there was NO air getting through the carb, for instance a plugged indy filter, then the plug should be wet and / or dark, like it was running rich, and the engine would stumble and misfire. As I mentioned, it is running nice and smooth.

I'll take the carb off and see if something is in there plugging the orifice on #2 nipple when the engine fires.

[MartyA]

Clamps around the carb manifold were all very loose. I tightened them, snipped 1" off the ends of the vacuum line, working fine now. I may have to re-clean the pickup coil race again, still seems a skosh binding, but the Mangler flew today.

Off to WV!!!