Wyly, I bought a couple of cans of Seafoam to try and so far have seen no difference.
After doing my usual mucking about trying different things and getting nowhere quick I was getting ready to stick a camera down into the carbs to see if a slide was sticking with the engine running.
In the shed was nice and quiet and nobody outside making any noise and the neighbours dog wasn`t barking as it usually does.
On starting the bike I heard a noise which wasn`t normal. A strange sucking of air and an audible squeak suggesting it was a leaking manifold rubber. But I had already replaced them with new.
I grabbed a can of WD40 and sprayed it onto the No1 manifold and the engine spluttered. It continued to do this with every spray.
I loosened the clamps and moved the rubber which was nice and soft due to the heat and retightened the clamps. No difference.
I sprayed onto the air cut valve cover, more out of frustration. The engine reacted again. And did so with every squirt.
Cutting the amount of spray to the smallest amount I could still got a response from the engine.
While feeling around for a leak around the valve I noticed the sucking/squeeking sound was being reflected back up to me.
On closer inspection I found 2 holes under the valve where they have drilled into the carb body to create passageways and then plugged them.
When I sprayed onto these plugs I once again got a response from the engine.
So for a quick fix/test I put some rubber sealant onto the plugs to try and stop the leak and left it to dry.
On restarting the engine the leak appears to be gone.
But the engine is noticeably running cleaner and I can rev it up to 7,000rpm with no sign of a misfire.
Hopefully tomorrow will be a nice day and I can get the beast out for a run as that will be the only way to know if I have found the problem.
Has anyone ever come across these plugs leaking before and causing problems?
Luckily for me it is on the outside of the No1 carb saving me from having to haul them all out.