[Turbospeed440]

After installing a new piston and jug on my sons 2 stroke predator 90 the battery can barely crank it over when it's cold. I can kick start it usually first try , once machine is warm the electric start works. I replaced the battery with an agm 5l class but that was not strong enough. I upgraded to a lifepro supposed to be 125 cca but nothing. I took my 270 cca battery from my outlander and that fired it right over.

Is this a know issue or is it a wiring or starter issue

 

[Mech]

So the engine's not tight when it's cold ?
Most quads seem to chew through starter brushes, so I'd probably pull the starter and check those.. It's an easy job, easier than trying to diagnose a slightly weak starter.. After that I'd start looking at all the starter cables and earths. Skinny or failing starter cables could give those symptoms, till the battery got fully charged to it's top voltage, when they become less of an issue.

 

[terrysclayton]

I had a similar issue on my kids 90. I replaced the the starter clutch and it starts great now. Here is the process: