the clutch shouldn't move when you hit it with the starter;
the clutch bell ONLY moves when the clutch is engaged (when the kart actually moves forward)
and that it mustn't when started.. soo clutch bell remains still when starting is correct!
Oil leaking at the back of the engine is usually just a gasket failure..
clean the engine with a rag as good as you can,
remove the spark plug boot (so it cannot fire up)
crank it over a few turns with the starter and see where the oil spillage originates from
the crankcase consists of two halves (split lengthwise right in the center)
three if you count the side cover (opposite from the clutch)
unfortunately that means complete disassembly to fix, but it's still a very simple fix.
as likely (say your engine not only leaks oil but it also lacks power)
is a cylinder base gasket failure
(remove head and cylinder to replace the gasket and retighten head to specs.)
it's fairly common if some (*cough*) filled the crankcase with oil like a four stroke engine...
the best thing that can happen is such cylinder base gasket failure,
the worst is the crank case cracks (say the cylinder studs pop free like when someone overtightened the head)
and such crack is actually the last thing that could cause such oil leakage...
But since everything at least looks decent at first glance, I have high hopes it's just a failed gasket.
I'm afraid that means you have to disassemble the engine (entirely if you want to be thorough!)
then replace all gaskets just to be sure, and retighten all bolts to manufacturers specs
(find the KT100 repair manual .. also replace all bolts with fresh ones!)
refit the cylinder (new gasket & fresh nuts to specs)
and retighten the mildly cleaned head to specs (again with fresh nuts and a new gasket)
TBH
personally while at it, I'd hone the cylinder and get fresh piston rings to match the size
and replace the bearings as well (case and conrod)
that way you end up with a completely overhauled engine.
All that is critically needed is to replace the failed gasket and retightening all bolts to specs,
but the engine is apart anyways.. soooo maybe that's a good time to at least measure wear and act accordingly.
'sid
PS parts available here:
https://cometkartsales.com/Yamaha-KT100-Parts/
the clutch bell ONLY moves when the clutch is engaged (when the kart actually moves forward)
and that it mustn't when started.. soo clutch bell remains still when starting is correct!
Oil leaking at the back of the engine is usually just a gasket failure..
clean the engine with a rag as good as you can,
remove the spark plug boot (so it cannot fire up)
crank it over a few turns with the starter and see where the oil spillage originates from
the crankcase consists of two halves (split lengthwise right in the center)
three if you count the side cover (opposite from the clutch)
unfortunately that means complete disassembly to fix, but it's still a very simple fix.
as likely (say your engine not only leaks oil but it also lacks power)
is a cylinder base gasket failure
(remove head and cylinder to replace the gasket and retighten head to specs.)
it's fairly common if some (*cough*) filled the crankcase with oil like a four stroke engine...
the best thing that can happen is such cylinder base gasket failure,
the worst is the crank case cracks (say the cylinder studs pop free like when someone overtightened the head)
and such crack is actually the last thing that could cause such oil leakage...
But since everything at least looks decent at first glance, I have high hopes it's just a failed gasket.
I'm afraid that means you have to disassemble the engine (entirely if you want to be thorough!)
then replace all gaskets just to be sure, and retighten all bolts to manufacturers specs
(find the KT100 repair manual .. also replace all bolts with fresh ones!)
refit the cylinder (new gasket & fresh nuts to specs)
and retighten the mildly cleaned head to specs (again with fresh nuts and a new gasket)
TBH
personally while at it, I'd hone the cylinder and get fresh piston rings to match the size
and replace the bearings as well (case and conrod)
that way you end up with a completely overhauled engine.
All that is critically needed is to replace the failed gasket and retightening all bolts to specs,
but the engine is apart anyways.. soooo maybe that's a good time to at least measure wear and act accordingly.
'sid
PS parts available here:
https://cometkartsales.com/Yamaha-KT100-Parts/