Orange????
1250 CC's.
NGK CR8EK or NGK CR8EiX (Iridium)
First disconnect your kill switch, if that is not it, check your plug cap, then if that is not it go on to your stator.
the stater needs to be rewound
Yes, Its located on the carby it's a black stick with a bulb ish end with curves.
Again it depends on which model you are asking about. A 520 SX (4-speed) will top out at around 70 mph depending on the gearing. The six speed 520 EXC will run 100 mph. It's not that the 520 SX is slow its just geared for the track and there's no motocross track that you would you run 80-100 at.
yes there is the ktm ktm 85 ktm 110 ktm 125 ktm 150 ktm 250 ktm 500
It would most likely be a SX or MXC. It could however be a EXC that someone has pulled the headlight and tailight off of.
I would first unhook the kill switch to make sure it is not shorted out. Next I would look at the stator.
ktm
The carburetor needs to be removed, disassembled, cleaned, reassembled and replaced. If any gaskets tear in the process you will need a rebuild kit.