Earlier I stated my engine was not working and i was going to replace the spark plug and ignition box, im happy to share that this worked. as long as the cylinder has a good oiled seal when you fire it for the first time. 4 stars because I had to put extra money into a model that really should have been in working condition to begin with. Runs pretty good, but i may want to mess with the part that the governor grabs onto (has a ball bearing on the end that rolls on the crank shaft) this part has a lot of side to side play, lowering the play room will help the engine spin at a more "consistent" rate (should be easy to fix if your model may require it), by that I mean it wont slow down as much during miss fires, this also makes it run a little bit faster. removing one governor spring is recommended by many people for slower prototypical operation (vary easy mod). One last fun thing you can do is tap a thread into a already existing hole on the crankshaft end ( do it on the side without the governor), this will let you mount a pully wheel or gear, now you can use your imagination on what you want it to power! Keep in mind its just a mini model, wont power your bike! Hope my reviews come in handy for the next guy to have trouble, or to anyone who wants to improve it.