After some needed repairs and 3 months later, my DT2 survivor is road worthy once again...so I thought. I took it out for its maiden voyage only to discover 5th gear jumping out between 40-50 mph. Have had 4 DT's over the years but never had a gearbox problem. Hoping nothing more then a  simple adjustment possibly ??

 Any advise greatly appreciated !

Check and make sure the shift drum detent plunger and spring are still there.  Looks like a drain plug underneath near the sprocket side and many ended up thrown out with the used oil. 

Yep they round off the edge of the dogs on 5th gear--both male & female dog slots that make up 5th & that would be the worst one. #rd gear was the other bad one. Also the high point of the selector drum at 'that' point although i'm not sure now if 5th on those came to the end of the selector track. 3rd will be at high point of the track & chip or wear off 'that point causing less engagement. Gear 5 & 7 in link below. Plus selector 10 in the second link if worn through trying to hold against the gear wanting to escape. Plus
www.partzilla.com/catalog/yamaha/motorcy...t2/transmissioncheck that 14 isn't broken & be good if it is because replacing might sort all the problem. I've broken those in racing but they updated to a solid pin in later models. Plus look hard at that center drum track. If its a full circle track then it'll have a high point to inspect. If that track comes to an end for 5th then won't be damaged. Mind you--look at the other gears & high points while in there--if ya go there. On one of mine i though damn i'm not going in there as had a roadrace the next weekend "DT2MX" so geared it high & only went to 4th. Whoops forgot link two. ps, no adjustment is going to fix this. Only saving grace will be in the plunger spring is broken or plunger stuck underneath on the left side. Also, increasing the spring tension with something heavier might mask the issue but only damages more what is already going on, so eventually the selector bends away with heat & pushing until 5th barely exists. Breath of fresh air aren't i--not lol.
www.partzilla.com/catalog/yamaha/motorcycle/1972/dt2/shifter-a

I removed the bolt to find the stopper cam missing. Spring looked fine. This part is N/A from Yamaha so assume eBay may be my best bet finding one. Seems pretty crazy to think this may be all that's needed to correct the problem. Or could this have caused damage by being left out for some time. I did notice after purchase, the oil was fresh. Possible the previous owner mistook this bolt for the drain plug in turn loosing or leaving out. Anyone have an extra cam stopper for sale ?

Lots of them on ebay...  $10 up shipped. 

Make sure your plunger isn't stuck if you haven't already...  usually both spring and plunger are missing.

Yes, it can cause the problem and yes if someone rode it a lot like that it would wear the dogs if it jumped out under power a lot.

But it's also the first thing to try and often fixes the issue. 

After I removed bolt and spring, I took a probe to see if stopper may have been stuck inside. I'm going to make sure by inspecting with a small mirror then order up. Hey Thanks so much MarkT

Here's an old post by Mako on the topic...  there are dozens more like it and many are success stories.

yamaha-enduros.com/index.php/forums/74-7...-gear?start=10#48164

Gosh, i'll eat my hat if that's all it is--& pull my head in. Ya sure the plunger hasn't rolled under the bench or in the oil tray. Without 'that' the gearlever would have a very non positive feel & be missing gears plus falling out of any gear you found & sure as hell wouldn't find neutral or only by luck. Wriggle the gear lever & it'll fall out on the floor. I can see about 20 hats in a stack haha. Any more & be covering the light switch.

Yep I made sure the plunger was not stuck or slipped by me. Now that you mentioned it, finding neutral has been nearly impossible during the few miles ridden. Ordered one off eBay yesterday. I pray no damage done, and the plunger alone will correct issue. Ripping into the gearbox is out for me. Will update.....

I installed the the cam stop yesterday, and immediately noticed a difference even before firing up. I proceeded to take a 30 mile ride to see if this simple but crucial part would correct the issue.

The crisp detents in every gear were quite noticeable and did not jump out of gear at all. Also believe no damage occurred while riding it some without the part. To ride this fully operational survivor again was a thrill to say the least. Felt like I had stepped back in time if only for a while. 

Thank You ALL for your help !