Just picked up a 74 DT360 enduro from original owner . He had told me it wouldn’t shift to 2nd. I’ve known him for a really long time. So when I go to buy the bike he starts it and I go up and down the street and it shifts fine. He’s blown away and said it didn’t work a few days ago.
So the other day I was riding in mostly 1st and 2nd gear in a circle and decide to go up and down my street and that’s when it wouldn’t downshift to 1st gear. It would do 2nd and 3rd and go into a false neutral in between. While in the false neutral if you let the clutch out it would make a clanking noise like piston slap or worse . Pull the clutch in and noise disappears. I’m thinking the shift drum spring or shift drum mechanism behind clutch basket is the culprit here? Any info from you guys is appreciated .

Jim

First thing to check is if the shift detent plunger and spring is still installed.

Looks like a drain plug bolt so many times someone has lost the parts. Looking under the bike, there are two "drain plugs". One near the middle of the trans and one over toward the chain side of the bike... the one over by the chain side holds the detent plunger and spring. Look at the parts diagram on Partzilla or in the service manual in the tech library here.

As MarkT says above. Probably 9 & 10 lying in previous owners oil drain tray. That bung is over on the left & by memory at an angle. think it has a 14 socket hex unlike the 17 hex drain further over.
www.babbittsonline.com/oemparts/a/yam/50...09bc7849d5/shifter-1
I'll just add that it must feel very non positive in operation of the lever by hand while moving the rear wheel when off the ground to let the gearbox dogs find their slot. Should feel a definite springy lump on the gear lever as it goes over the high point & into the next--as in item No5.

Thanks guys I will give that a try. If all the parts are there I’m thinking clutch basket needs removed?
Thanks in advance

Jim

What I noticed was there was a little play up and down on gear shift lever. Say a 1/4” ?

ok, if it was stuck between gears the there would be movement each way of an equal amount until the claw arm contacted the pin to pull it further into gear of back to the previous gear depending which way you're moving it. I'm guessing you don't just mean simple play of a loose gear lever on the spline'd shaft?. I'll stick to the missing plunger & spring theory for now, or at least one item missing if not both.

Yamaha started using the same part for the drain plug and detent plug at some point so wrench size isn't always a tell. Picture from manual of detent plug being removed might help.

Just changed my wording in post #6 as mistakenly put wouldn't instead of 'would' 'which is what i meant'. Brain fade typo.

Exactly not looseness of lever on shaft.

I have had the change lever jump a tooth and act much the same. I replaced the seal next to the shift peddle and pushed the shaft enough to make the change lever 1 and 2 come out of position. If so you will need to pull the clutch cover and reposition , there are alignment marks on the change levers