oldduke

Hi just joined been a biker for 50+ years and recently brought an unloved unused xj 600 back to life to keep myself from becoming a couch potato this winter! First in line four ever owned having almost every other shape and size over the years. Now riding with both wheels on the tarmac but still enjoying biking!

Hi Untold I've just completed a similar project and to get the manifold/inlet rubbers and carbs checked I did the following. I removed all carburettors removed all the diaphragm covers found one slide to be sticking so cleared this ok and found one of the diaphragms to be missplaced allowing the slide to drop/not rise in a controlled fashion with vacuum. Next reassembled and using a single vacuum gauge check each inlet rubber in turn off its vacuum hose whilst ensuring the other three were bunged up (using the priming position on the fuel tap so no vacuum was needed here. This will do two things it will show if each carb is balanced and in your case more importantly (if there is a very low vaccuum) show you have an air leak which could well present the symptoms you describe. If there is a low vacuum then its a case of seeing whether or not that manifold rubber is to blame or the seal with the cylinder head or carburettor joint is at fault. Hope this is of use.