Hello to all.
I have a 1974 DT250 that has a drip from the clutch shaft seal on the bottom of the engine. This is the shaft with the lever under motor where the clutch cable connects.
The question is as follows......I have seen a video claiming that you can
Step one......Release the clutch adjusting screw behind the left engine cover where the primary drive sprocket is. Remove it completely.
Step two....... The clutch shaft should then drop right out. (Keeping in mind the orientation of the flats on the shaft up in motor)
Step three..... Pluck old seal out of bottom of motor and install new one.
Step four....... Reinstall clutch shaft (in proper orientation) and reinstall clutch adjustment screw.
Sounds simple. (Probably too good to be true)

The shop manual shows splitting the cases to do the same thing.
Is it possible to replace the leaking seal without splitting the cases? And if so, I would be grateful for any knowledge shared on this subject.
Sincerely

I've never done this except during a complete teardown but it should be possible.

You might have to remove the clutch side cover and the clutch pressure plate to allow the pushrod to move out of the way enough of the wedge to pull the arm out. 

Might want to have bike leaning to right to avoid pushrod from sliding over and preventing re-installation.  Also keep an eye out for short pushrod and ball falling out with pressure plate off. (Might want to just remove them so the ball doesn't get lost)

So ya talking #23. I'd lay bike right over flat on it's right side so you can see what ya doing, then unhook cable.
Then adjuster lock nut, then wind adjuster counterclockwise while arm goes up & down until adjuster falls out--& disengages.
Then actuator arm should fall out if you turn it away from the pushrod.
Away will be opposite way to cable pull direction.
Then carefully flick seal out with screwdriver.
Grease the new one & push in.
Assembly should go well but will need to have the arm around to get past [or beside] the pushrod.
Then feel the adjuster engage in the arm as you screw it in.
If you screw in too far & goes tight just back it out so you can get a full movement of adjustment up & down.
Ya only get a half turn of adjustment by lifting or lowering the arm which you will see has a very tapered flat end that bares [bears] on the pushrod.
Should be a casting mark under the case to give an approximate ideal angle for lift but depending on the cable you might need to slightly ignore the mark.
Sorry if i'm shortcutting words.
Correct me anyone if i'm wrong--been 50 years since doing that at work lol.

www.partzilla.com/catalog/yamaha/motorcycle/1974/dt250a/clutch

Greetings from Tennessee. 

Hey MARKT and RT325<
I really appreciate the feedback. I was hoping to accomplish the replacement without splitting cases. Sounds like you can. I will follow these instructions carefully. I did research and I am aware of the pushrod concern when reinstalling the clutch shaft. Thanks for recommending laying over on right side.
I will report back with the outcome. If it goes from sugar to S...., I will let you know.
Thanks again for your info.
Sincerely

I would try it without loosening/removing the clutch pressure plate under the clutch cover first.  But if the lever won't pull out, it could be the pushrod is against the "wedge" of the arm.

There is a groove in the clutch arm shaft that the offset pin in the adjustment screw fits into.  As you rotate the adjustment screw to get the correct internal freeplay, it simply raises and lowers the entire clutch arm.  It only takes one half turn of the adjustment screw to go from minimum freeplay to maximum freeplay.

I've drawn the pushrod in red in the photo below...  as you can hopefully see, if the arm moved down the wedge gets thicker which would reduce any internal freeplay.  As the arm moves up, the gap between the wedge and the pushrod gets bigger, increasing internal freeplay.

But as you can see, you might not be able pull the arm out unless the pushrod clears the wedge, which in my experience with the 175's, it won't unless the clutch pressure plate is loosened or removed to allow the pushrod to move over enough. 

Says clutch rod seal but realy means actuator arm seal.

RT325  Nice video find! 

(I still say it's possible the arm won't pull out, trapped by wedge, especially if clutch has worn.)

Hi Mark, just my opinion but i think the taper turn away & around the side of the pushrod so couldn't see fiber plate wear stopping it coming out.
All good. We wait. Cheers.
ps to OP just be careful engaging the tit of the adjuster in the actuator groove.
Think he shows it adjusting & looks like he's turning constantly but in reality when engaged & in about a turn then he is only going a half turn clock & half anticlock which is your total adjustment movement.
He doesn't hook the cable on & set the arm for cable play or optimum pull angle, but good video none the less.
On second thoughts maybe he has set the arm to an alignment casting mark.
Might be where the spring hooks on, not sure
My useless laptop won't play without buffering. I'll watch it later.

RT325, If you could turn it sideways I'm not sure how it would press on the pushrod?  However it may have enough clearance to pull straight down without messing with the pressure plate? 

Good tips and great advice on getting the eccentric pin lined up in the groove on assembly!