Vacuum Advance Test Help Please

[silloyd]

Just a quickie...I know you can test the vacuum on the dizzy by sucking the pipe to the dizzy and watching the base plate.

My questions are how much should it move and having moved, should it hold it's position until you stop sucking?

[AlMcL]

Dont know how far it should move but if you suck on the end of pipe and then keep your tounge on the end of pipe the plate should not move back if it does the problem could be either the seal on the pipe or the diaphram itself.hope this helps.
Allan

[silloyd]

Allan,

Thanks, that certainly helps in part, as mine won't hold the vacuum but I'm not sure where the leak is yet - I suspect the pipe to the carb.

Would still like to know how much it should move, if anyone else can let me know please.

[AlMcL]

I had same problem with mine it was the pipe all I done was to super glue the pipe and elbow no more leak.
Regards
Allan

[bmcecosse]

Hard to say exactly how much it should move - be happy if it moves about 5/16 to 3/8" and falls back when you stop sucking. Your lungs can't suck as hard as the engine can!

[silloyd]

Thanks BMC. I'll sort the vacuum seal first and see what happens; I think a new pipe or at least rubber ends may be necessary

In the mean time, can I check for free movement in the baseplate by applying mechanical pressure with (say) a screwdriver? If so, where do I press (pic would be ideal if possible).

Thanks all.

[bmcecosse]

Well yes - you can test if it's free to twist round - it usually is unless the dizzy has been lying about for a long time. It's the vacuum unit that fails.