Yamaha xj650 running problems

[twostroketit]

My !982 XJ650 is not running on four cylinders at low revs.

If i pull number one plug cap off at tickover there is no change to the engine note.

If i take the engine up to about three or four thousand revs and then pull the cap off the revs die, when i replace it the revs build up again.

I have changed the plugs and put another coil on it, but no change.

I did suspect a torn diaghram on number one carb put i just had a look and it's fine.
The problem gets worse after about five miles of riding which makes it even more difficult for me to to find a cure.
Anyone got any ideas?
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[stickybackbob]

Have you checked pilot jets and valve clearances?

Can't remember if old xj's are on points or not. If they are check them. If not, check the connectors from the pick up, CDI and points. They need to be clean and tight.

Hope this helps