Geo 1.0L Vibration is kicken my BUTT

[Jeffreygab]

New to the list and hoping to come up with a useful solution.
My metro 1.0l has about 50 hours of run time total since rebuilt. It has a vibration at 3500 rpm that is pretty sever but smoothe right out at 4500 and up. The idle is rough but not HORRIBLE.
I ahve checked:
Plugs and wires
FDistributor replaced with rotor
Plug replaced
compression test
Removed all attatchments to the crank except flywheel and test run it
Removed flywheel and bought a new one and test run it
I checked to make sure the crank seals were not leaking which might indicate bas crak bearings and run out
I do not notice any unusual noise in the engine that owuld indicate bad rod bearings. And certainly under load there is no noise.
The rpm range is 900 rpm roughter idle but livable
2500 rpm vibration pronounced but not horrible
3500 rpm vibration can be felt in seat 4500 rpm vibration seems to get better
5500 rpm can not feel it at all

HELP! PLEASE

[Arnoldtheskier]

When did the vibration start?..AFTER the rebuild I am guessing...

Was the ORIGINAL non vibrating engine rebuilt?
What parts were changed?..
Vibrations can be caused by so many things in the reciprocating assembly.. Change one part/move one part that is not within specifications OR too different from the other ones..and the vibes can start.

Perhaps you could start by trying to isolate the vibration severity to a particular cylinder.Even a new plug or wire can sometimes be not as good as it should be.Maybe switch them.

Sometimes you can be pretty safe in assuring that the vibration is NOT related to power..BUT is in fact in the reciprocating assembly.You should definitely try and isolate the vibration as to whether it occurs AS you are revving the engine up..OR as it is slowing down.Perhaps under load accelerating too..or coasting down.

IF you find that no matter what you do..accelerating/decelerating..load/no load..that the vibration does NOT change..I am guessing that it was caused when the engine was rebuilt..somewhere in the reciprocating assembly.