1998 Kawasaki 1100 Stx losing power

[dlogvine]

I got a 1998 Kawasaki 1100 STX with taken apart engine. Put it together, new gasket sets, rebuild carburator. Compression in all cylinders was even 125psi +-1 or 2. Spark was good on all plugs. Was running fine on the water hose, but took some starting fluid to get ti going. On the lake started with about 25-30 mph but felt that it was not going full speed, looked like it was for a split of a second going to rev all the way on WOT but then was going back. After 15-20 minutes of running (I hoped it might be old fuel in the fuel lines or carb jets that would clean up from running) it started choking and all the way back i was going at about 9-12mph with engine running very weak and choking all the time. On the shore did start and ran pretty well. Replaced carburator and the same story repeated, also this time it took about 25 minutes for it to start choking. Im planning on replacing all the fuel lines, since the problem seems to be in fuel delivery. There is supposed to be some pressure valve in the tank that might be bad?
My question is what should i do to determine the source of the problem. Also starting it requires starting fuel every time after a day since the previous start. I now 2 stroke Kawasaki are notorious for bad starting, but not this bad.
Thank you

 

[ejnichol]

How many hours on motor? Did you measure the bore, hone or replace rings?

Even though compression test good it feels like a tired motor in need of rings. But sure there could be some other explanation.

 

[dlogvine]

How many hours on motor? Did you measure the bore, hone or replace rings?

Even though compression test good it feels like a tired motor in need of rings. But sure there could be some other explanation.

Thats a great question. There is no hour meter in the cluster, so the answer is who knows. Looking at the walls of the cylinders, no scuffs or scratches. top end is also in a good condition. And tbh, I've never heard about the engine running with a good compression on bad cylinders/pistons/rings. The trouble is somewhere in the fuel line, tough to start, chokes after running for 30 mins, not immediately.

 

[ejnichol]

What about fuel pickup, fuel filter or pump? I've rigged up temporary fuel tank, lines and pick up to feed fuel pump to make sure tank or pickup wasn't causing fuel starvation. Harder to do on pwc though.

 

[dlogvine]

What about fuel pickup, fuel filter or pump? I've rigged up temporary fuel tank, lines and pick up to feed fuel pump to make sure tank or pickup wasn't causing fuel starvation. Harder to do on pwc though.

it would be hard since on the land the engine is running ok, it is in the lake after a little while the power is dropping. Fuel filter is new, pump is gravitational inside of the carburator. I was going to take it apart to see if there could be any issues