Suzuki 2 Strokes

I'm having issues with my starter motor, I removed it, cleaned it all up and put it back in. It seemed to spin up OK but I was holding the earth strap onto the battery and it heated up so much I had to drop the cable lol. I am thinking that because the 550 engine is rubber mounted that my earthing strap is insufficient. The bike is still in rebuild and the ram-air covers are off and therefore the top end earth is not connected, would this be a good reason for the heating up of the main earth strap I was holding onto the battery post? I created a short earth wire from frame down by brake light switch mounting to back of motor, it isn't very heavy gauge. Many parts of this bike were missing when purchased so I'm floundering a bit with some areas of the rebuild.

You are right about the engine being rubber mounted needing a ground for the starter motor. the ground strap from the frame to the engine should be as heavy gauge as the positive cable to the starter, as well as from battery to frame. the ground cable to the ram cover is not for current carrying of the starter, if you don't have a big enough ground strap from frame to engine, you will melt the ram cover ground in the harness, and any other wire around it.

Cheers, I will add a heavy duty cable from the frame to the engine case and see if that cures my problems.

The GT550 should have two ground wires connected to the battery negative terminal.
A regular thickness wires runs from the battery negative to the frame near the battery box.
An extra heavy wire runs from the battery negative to a motor bolt near the transmission oil fill cap.

On early GT550s the extra heavy wire was an uninsulated grounding strap.
This used eBay motor shows the grounding strap & regular thickness wire. Both wires are crimped into a single battery connector.
https://www.ebay.com/itm/Suzuki-GT-550- ... 2789584912

OK I shall fit a long cable from the battery negative to the case bolt near the oil filler, the type of battery I am using has two mounting points on the earth post.

Added new heavy gauge battery cable to connect the engine to the battery, pressed button and she spins beautifully, thanks guys, I can chalk another thing off my long list on this bike.