Very rare for starters to get "lazy" Most either have worn brushes, easily replaced, or oil inside, again easily cleaned out. Those with "naked" magnets can have a magnet come off, in which case the starter is toast, but take it apart and find out. Warning, most are swines to get back together though.

 

I know this is an old thread, but I'm having a similar problem and the answer isn't here. Motor turning over slowly even with fully charged battery with assistance from car battery. I've tried a couple starters with the same results. I've removed the carburetor and exhaust. I've also just ran the starter directly to the battery, eliminating the wiring harness, and it still turns over slow. Sometimes it does crank normally and then slows down. The valves are adjusted right. It even gets up to 150psi when I get it to crank, but it just won't stay cranking. Starters both work fine on bench test. Any more ideas????

 

Ended up being a bad one way clutch. Replaced it and it fires right up.

 

Anyone find a fix. I知 having the same problem. It has spark and compression. Has fuel. It痴 not the starter, starter relay, timing, wires, or starter clutch. Is there anyway it can be the carb? Cranks over for a second or 2 until it gets hard then gets over the hard spot and cranks over and repeats. Battery is good. Help please

 

Some two strokes (the LT80 is famous for it) can fill the sump with fuel overnight, then pump it into the cylinder, where it hydraulically locks the piston. This is caused by a leaky fuel tap and float needle in the carb. However, once it locks, you need to take the plug out to free it, so my guess is that one of those parts you listed as OK, aren't. Only thing you didn't list, that it could be, is a partly seized engine.

 

I知 talking about the Chinese 4 story me 4 wheelers. I know it痴 not locked up and it cranks over great with spark plug out. I知 replacing the wire harness

 

That won't work. The starter circuit is, good connections from battery to solenoid, to starter, on the pos side, and good connections from battery to frame, to engine, on the negative side. The rest of the wiring loom just ensures the solenoid clicks in when you press the start button, which it already does. I once fitted thicker starter wires in an attempt to speed the starter. The fault turned out to be the one way clutch (see my posts above) however once the clutch was fixed, the thick wires did seem to be giving the starter a boost.

 

You say one way clutch as in the starter clutch. I知 also replacing that.

 

this did not work nor did the wire harness. I知 stuck

 

As I wrote above, good connections on the thick wires, including earths are vital. You wrote that battery and starter are good, how do you know?