Club 80-90 Forums

Ok I have thread on the other forum because my blos won't work But now the mystery deepens. This could be due to a lack of vacuum at the unit which opens the second choke of the carb. Ive just replaced the vacuum hose to be safe and checked the operation of the vacuum unit and hey presto when you apply a vacuum and open the throttle up the second choke opens. Only problem is that from the spur on the carb that feeds this no vacuum appears. It must be blocked!!! I tried putting my tongue on the end of the tube and could feel almost nothing. Now the other vacuum spurs for the dizzy and air filter try to turn my tongue inside out and I can hear the vacuum. So is the strength of this vacuum the same as the other spurs or is it supposed to be different. And how does one unblock it? Or can I use the spare spur that I have that used to feed the intake?

vacuum is different for the 2nd throttle and comes from drillings deep in the carb throttles the other to vac ports come from just below throttle.

I would use compressed air to blow it through.

I should add vacuum above the throttles at idle will be low, compared with vacuum below throttles.
See if you can blow/suck through the port spigot, then place a finger over each port hole in the throttle ons at a time and check you can blow through the other, then finger on both holes should seal the port, really need to take the carb top off though.

I tried to feel the vacuum at idle and at near full throttle with no real change. I sort of assumed it would be obvious? There was no change in engine note on unplugging it either. I will squirt some carb cleaner down it and then attack it with an old guitar string!! Then finally I will try some compressed air. Thanks for the pic, very useful.

In for a penny and in for a pound, I attacked the vacuum stub with a 0.5mm drill in a flexible shaft after seeing and reading Itchyfeet and Ghosts posts showing that a 0.5mm wire would go through into the drilling. The deposits were like a calcium/ hard powdery build up which I drilled through into the drillings. I could now blow down the stub so was expecting to get some vacuum but after connecting the gauge no such luck even at half and full throttle.
So what do I make of this? I realise that the stub is fed by a drilling opening out into both chokes above the throttles so would not expect much vacuum at idle. However I would expect vacuum from the main choke with the throttle opened up. I would expect this to build up and start to operate the vacuum valve to open the second choke which would add vacuum from this side opening the second choke wider. Unfortunately my gauge was not flinching so do I assume that the passage to the main choke is blocked and I am blowing air through to the second choke in which there will be no vacuum as it is shut? Or infact is there not enough vacuum unless there is a load on the engine, in which case how can I tell if the second choke is opening? (This would be a bad outcome as this would mean that the second choke not opening was not the reason for my blos not working properly!!!)
Carb off at the weekend to get to the bottom of this I think.