engine surging

[wolf]

I have a 1986 90ETLJ - At higher RPM's it starts to surge & the engine shakes violently. This usually happens when the engine is cold but can happen any time. If I accelerate slowly I can sometimes get it to run smoothly. It seems once I have it running it will run the rest of the day- no problem It started out happening occasionly but now happens just about every time I go out.
I have checked:
The fuel tank(inboard)-it's clean
Replaced most of the fuel line
Replaced the ball
Replaced fuel filters
Replaced spark plugs
I am running out of ideas - Can anyone Help
Thanks

[jb123]

remove the fuel line junction at motor, run line directly to motor filter, use an auxillary tank, run motor and see if you have any different results. most likely need to clean carbs. As a precaution I would do a compression check also.
then you can run motor at about 1500 rpms and pull each plug wire at at time, listening for a distinctive rpm change and if none, that cylinder isnt functioning correctly. then pull your airbx and run, choking each throat with your finger, listening for improvement to check for a clogged carb.

DO YOU use a water seperator, hopefully.

[ April 08, 2007, 11:47 AM: Message edited by: jb123 ]