Vacuum advance

[bmcecosse]

Some vacuum take off points are designed to be 'hidden' by the throttle plate at idle....... Connect the gauge - rev up and then 'almost' close the throttle - what does it read as the engine slows........

[Arthurdaily]

I'll check that tomorrow. Thank you BMC.

However, that means then that there would be NO advance at idle? I though it was supposed to advance then AND whilst cruising??

[bmcecosse]

I don't like it - but that's the way some are designed - where the take off is on the carb body itself. I prefer to take the vac from the manifold. But even with the carb body system - you will have the throttle slightly open when 'cruising'....and so vac will be present at the dizzy.

[Arthurdaily]

Could it also simply be there is a massiv air leak into the manifold?

[bmcecosse]

Yes - if the engine doesn't run........

[Arthurdaily]

Ah, right, yes. I shall do throttle open and close experiment and report back.

[Arthurdaily]

Right, done as asked BMC with TWO vacuum gauges, neither show any vacuum present at any time during experimental revving and dropping to almost idle! Not even a twinge of vacuum movement.

[MarkyB]

stuck a pipe cleaner in, and it does not appear blocked.

Did you see the other end inside the carb?
At the end of the day it's a hole, very little to go wrong.
I'm thinking a picture might help.

[bmcecosse]

Do the gauges work? Suck them - how much vac can you make ?? I've forgotten now why you want to measure the vacuum - vacuum gauge is the most useless thing ever.......except on my steam loco of course - where I have TWO !!

[Arthurdaily]

They are not 'gauges' as such... why would I fit one? They are just 'test' gauges for checking vacuum. Now EVERYBODY here seems to go on about the importance of vacuum, including you... BUT mine doesn't work, there is no suck... so of COURSE I'm curious as to why this is the case...

The gauges DO work though - I have attached them to another Minor in my care and they register vacuum.

[liammonty]

The carb on your Minor (if it's an HS2 the same as on mine) will blank off the vacuum at idle. You'll get most vacuum just off idle, not if you're revving the thing up like mad, when you'll have no vacuum either. TBH though, it's really not possible that there is no suction coming from the carb if there's no blockage in the vacuum take-off on the carb. Life's too short for this- I would stop worrying!

[bmcecosse]

[Arthurdaily]

Took carb off - somebody had 'glued' a strip of what look like plasticated paper over the hole inside! The gauge now reads as it should...

I'm happy now and will never mention vacuum ever again

[bmcecosse]

We are delirious............
But - you had poked a pipe cleaner through...? Is the engine running better now?

[Arthurdaily]

Clearly not far enough, does it run better? Well, with a little throttle (for example during cold choke moments) it runs a little faster - plus perhaps a little smoother on pick up.

[les]

You'd never make a chimney sweep!

[Arthurdaily]

Ha ha, it would be more my incredible girth than my attention to orifice-cleaning detail that would negate the possibility of that particular occupational avenue I think...

[les]

It's the brush that pokes out the top, not you!