Sean,
Yes there is, but I have never done it. First, I would consider simply changing the rear sprocket to 50T. The 46T you have on there is too tall to do you much good. You may have to use a longer chain as a result of going to 50T, but for street riding it may be just what you want. It is very likely that if it feels way to tall for you that you do in fact have the Intermediate gears.
To get back to the gears you can look at MO12 in the spares manual. What you would like is the MK2 gears which shows a ratio of 1:2.60. This means, if I am correct, that for every 2.6 revolutions of the engine the counter shaft sprocket rotates once. Thus, in fourth gear, which is 1:1, the engine rotates once and the CS sprocket rotates once, giving the highest speed.
The Intermediate cluster is 1:2.07. So, the engine is moving only 2.07 revolutions per CS sprocket revolution. If you take out the plugs and move the the rear wheel you could mark the CS sprocket and see if it turns twice or two and a half times. Alternatively, you might try counting links from a particular reference point. The CS sprocket is most likely 21 teeth as that is the stock item. You could count the links that go by in two engine revolutions in first gear starting at TDC and it will probably be 43, which is the Intermediate ratio.
Good luck!
David