Problem shifting into 1st gear.

[jgas]

My 01 XC sometimes doesn't want to shift down into first. I can usually tap the shifter several times or shift up from 2nd to 3rd, then quickly back down and it will go into first but sometimes this doesn't work. When this problem occurs the gearbox just goes into neutral but won't go to first. If I stop and shut the bike off, then restart it, the problem usually goes away for awhile, sometimes for hours, sometimes only for minutes. When the problem goes away the shifting is smooth and normal. The clutch is working fine, the shifter is tight on the shaft. All the other gears are ok, shifting both up and down. The fluid level is ok and the shifting is smooth through all the other gears.

I had this problem on a well used 89 KDX 200 with a ton of hrs on it and was told to put automotive synthetic transmission fluid in the gearbox which I did and fixed the problem, and the shifting was a little smoother as well. My XC is an 01 but doesn't have alot of hrs on it, it was stored and not ridden for several years so the hrs are very low for an 01. Would the synthetic fluid help the XC, if not where do I start looking to find the problem?