Starter motor slow cranking/electrical wiring questions

[chopyouup]

Alright, hopefully someone can help me. This 50cc scooter was repaired with a 60cc kit (jug piston head ect). I can not for the life of me get this scooter to start with the starter motor only, kick start is just fine.

Here is what happens,

Under no load (bendix removed) the starter motor spins freely, with bendix installed the motor turns and slows/stops at the compression stroke then rolls through (this is pitiful sounding and will not spin up the motor).

I can kick start it just fine, idles fine, rides great.

So I thought it might be a voltage issue, replaced wiring [batt+ > solenoid in] and [solenoid out > starter].

Ok next tried a car battery (both on battery terminals and on the starter motor it self), no go.

Better voltage reading now at the starter terminals when engaged, but still slow as before.

Alright, must be a compression problem, no compression tester so I added more base gaskets, more head gaskets, was running (kick start only) as 2base 1 head
tried 4 base 2 head still no luck! This is now so large then is quite a distance between the piston head and the edge of the cylinder at top dead center.

So now I am wondering if it could be just a bad starter, or my grounds wires are bad.

What wires should be grounded, where should they be ect. I think the only ground I have seen is from the Bat- to the case (right at the bolt in the starter motor to the case).

Thanks!