I do enjoy riding in tight woods at times but I don't know how much fun that will be on a big bore Maico?
That's my worry as well, esp. b/c it's an MX transmission. So, my 1982 isn't geared too shabby, it's a GS model and it's the older motor.
However, now going into the 83, the 83 I originally had the Spider gearing, which is a 4 Speed where first gear is 2.07 ratio. When I was riding this I was originally riding wider open trails, so wasn't so bad, but now I ride almost exclusively single track.
I switched to the sand spider gearing, 5 speed, 1st gear is 2.36. This was STILL quite high, had to do too much clutch and this I still had a 14 Front and 56 Rear. So now I have a 12 front and a 58 rear. It's much better, however the thing is extremely torquey on the high RPM.
Now, my 1986 as you see in the video, forget about it. In 1985 and onwards they changed the gearing to be super high. Primary drive is higher and first gear by stock is 1.96. So, on my 1986, I am putting a 1983 primary drive and I got a new 1st and 2nd gear from Koestler. They don't make the sand spider ratio (2.36), their enduro 1st gear ratio is 2.28. So, I think that with this and a 12 tooth on the front and maybe even keeping the 52 on the rear may be good.
Flywheel wieght may help tone down the torquey ness of the motor, but the motor DOES pull from low RPM. The problem is that "LOW RPM == 20-30 MPH!" So, at idle you're going fast! Also, most of these have internal rotors and not actual fly wheels. HOwever, you can get wieghts for PVL rotors.
BTW, the ratios on my 86 match the new bikes. They probably match the 98's also. The 500, 620 and 685 have the same transmission ratios and primary ratios. The 250, 320 have the same transmission ratios even as the 500's, however their primary drive ratios are lower.
In the end, for gas milage if one plans to do some events and for gearing, the 98 320 enduro might be a good option. A 1.96 1st gear ratio for MX is quite high for tight trails.