Goes into first no Problem grinds at second

[vint1100s]

Hello again and thanks for all the ideas. I have the transmission out and find that the #1 shift fork is wearing on the inside face as a result of not being able to encourage 2nd gear to engage. The gear it is attemting to move is only battering the face of its mate(large gear) in an attempt to mesh with the slots. I can provide pictures if there is a way to do that.
I do not have a slipping out of gear problem but a failure to sync problem. The previous owner says he could ride in 3rd but had to skip 2nd.
The shift forks look fine and gear contact surfaces are barely showing wear so i am hoping someone can explain how the gears sync or the mechanics of a spinning transmission so i can trouble shoot it. The transmission works perfectly when on the bench turning the wheel by hand.
Help!
P.S. The shift drum and pins/star keeper are all in tact so the extra pin looks to be from a previous fix and left in the trani pan.

[motoman]

Now that you have that shaft/gear assembly out, remove the gears from shaft and following the shape of the loaded side(shiney side) of those ears dremal them with a diamond stone with ever so slight an angle(dovetail). Some, but not in all cases the engagement depth is not far enough causing an ever so slight rounded edge of the dogs. It sometimes will look no different than a bit of wear, but will slip back out of slots under load. Do not put it back together without correcting, unless you like repeating the initial process of tear-down. The gears affected I believe are also still available from Yammy already corrected if you want to go that route, but over a $100 a pop. Some also swap position of the thrust washer to allow farther engagement. Was not my choice for two reasons, goes against my better judement to have anything loaded against a snap ring without a thrust washer. Second, in my trannys case the dogs showed wear from FULL engagement. Your choice, doesn't seem to be an issue thus far either way. Nothing else to really trouble shoot. Important when assembling and once together to make sure the two marks on the shift pawl line up when in second gear and the spring on the shift mechanism is properly installed. If these two things are not correct, it will still exibit shifting issues.