Car only runs with vacuum pipe removed!

[Mike from Spain]

Runs like a bag of spanners with vacuum pipe connected. Disconnect and it runs great. Suck the tube and engine note falters (so advance/retard would seem to be working) put finger over over tube on carb (the one I disconnected the vacuum pipe from) and nothing happens. Can this be blocked? Anyone had a similar problem? All new electrics inc. leads and carb cleaned out today. It's an '89 1100 model.

 

[mr-reno-139]

Sometimes the points aren't fitted correctly and the vacuum pulls the them at an angle seriously affecting points gap
If you have got a dwell meter see what happens should be 57 plus or minus 3 across whole rev range even connected

 

[Mike from Spain]

Sometimes the points aren't fitted correctly and the vacuum pulls the them at an angle seriously affecting points gap
If you have got a dwell meter see what happens should be 57 plus or minus 3 across whole rev range even connected

Thanks for that. I gapped the points and when I was doing that I thought they didn't look right! As if the contact had fallen off one side? I'll check them later.

 

[Mike from Spain]

Sorry for late reply but only just got around to tinkering! I changed the points and because I wasn't sure that the vacuum spiggot pipe coming out of the carb was sucking properly I decided to lift the carb off and check. It was clear but what I did find was a chunk of the gasket was missing! When I put it back together it ran ok with the vacuum pipe connected! So, we're not sure about the original problem but seems to be a choice between the two! It's still lumpy on tickover though despite everything electrical being renewed (including the leads) and the head gasket being recently replaced?

 

[mr-reno-139]

After you replaced gasket did you check valve clearances
Also when the head was off were the valves ok
Further thoughts would be loose manifold nuts or did you reuse original manifold gasket and now leaking air in

 

[Mike from Spain]

I didn't do the work on the head but my neighbour says he trusts the guy who did the head! I'm going to have another tinker with it during the week and maybe I'll check the compression whilst I'm at it! Will keep you posted.