Motorcycle license in Japan?

I'm almost done with my studies here in the US and am planning on going to Japan to work for a bit. I am almost done getting my master's degree in English although...my question being is it difficult to get my motorcycle license in Japan? I've been riding for a good 4 years and wouldn't let it go for the world. I'm currently riding a Ninja 650R and..are there certain restrictions on how big your bike can be according to it's holder's License? Tests? Writing Tests? Just curious if I do get a job there ( pretty positive) I would like to have transportation just not a cage (car in motorcycle slang lol)

If you only plan to be here for a while you will be covered to drive whatever you are licensed to drive on your international driving license for your first year. A mid-sized bike like the one you drive is covered by a "chu-gata" license .Anything bigger is "O-gata". You can rent or buy a bike quite easily as long as you have the correct license. It is the law here to wear a helmet. You will get stopped and charged if you don't. Insurance is also a must and is not very expensive.If you stay for longer then a year you have to get a Japanese license. I'm not American so I just had to answer a few questions but I do know that some countries have to do the full driving test. There are driving schools that most people usually go to in their teens. It seems if you attend these schools and pay the fees you will get a license no matter how terrible a driver you are (and there are many on the roads here). You can just pay to take the test but they will however fail you numerous times coz you didn't go to the school. In Japan for Japanese people the drivers license is seen as a "certificate of competency". Most potential employers would think, "if your that stupid you can't pass your driving test your too stupid to work for me".
The rules or the road and most of the road signs are almost the same as U.K N.Z and Ireland. a lot of the highway signs are in English too but not all.
You'll enjoy driving here if you drive defensively.

Hm, I actually did take a Motorcycle safety course here in Southern California, And it did allow me to skip the writing portion of the motorcycle license test a few years back. It did help and I do follow AGATT All the time( All Gear All The Time). I am a defensive driver and not an aggressive so I'll look into it more.