Hey everyone, I’m working on getting my DT360 going again after it had an accident a while back. Got into a bunch of oiling issues as it was filling the case with 2T. Fixed that but discovered an interesting looking roll pin while adjusting the oil pump again. The roll pin that the throttle pulley ramp rides on seems to be missing a piece that corresponds to the area the ramp rides on. Almost looks like it was worn or cut in by the ramp, but the ramp surface looks fine (see pic). I’ve never seen the half roll pin on any of my GT80s or my DT175, it’s always a full cylindrical pin on those. Anyone with a 250/360/400 able to chime in on this? 

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I wonder if the pin has been replaced at some point with a generic roll pin .
I don't know , but perhaps the Yamaha OEM pin is hardened .
The pin rubs on the Pulley Ramp every time you open and close the throttle .
So over thousands of miles , a soft pin could wear appreciably .
I'd replace the pin with a genuine part , and check the plunger shaft shim clearance afterwards .

Seems there's a first for everything around here.
Not original thats for sure.
Later pumps by memory had a threaded pin with a very small hex & a step to stop turning in too far.
Now, if you fit a new roll pin be very careful not to insert until it contacts the shaft as can stop it moving, or it'll force it out to max stroke but won't return for the next mouthful.
It's not well thought out the roll pin thingy but i guess in theory its not meant to be ever touched by us home mechanics.

Anyone got pics of a 360 oil pump if it is supposed to have the roll pin or the threaded pin? I can't find anything in the manual, and no P/N listed for the pin. Couldn't find a P/N in the pump rebuild threads either as it was never really supposed to be taken apart by us.

I'm guessing it would be too early for the threaded pin & thinking it might not have the bent plate to stop it falling out 'if threaded'.
Could be proven wrong though.
Found this link by googling for a threaded guide pin which comes back to this site anyway i think. Maybe no use but anyway.
yamaha-enduros.com/index.php/10-referenc...-rebuild-an-oil-pump
You can clearly see the threaded pin in this pic.
photos.app.goo.gl/QGv3hTp49MbgQLqh9
 

Older parts books do show the pin as a separate part # 91608-20010 .
This is for a DT1 , but as these pump bodies are all the same size , ( externally at least ) ,
I'm sure this will do the trick . I haven't checked to see if it is still available either . though
the part number could conceivably have been superceded .

If you 'do' ever happen to have a roll pin out & want to re-use it, just fit it in the other way around as it is likely to makes it that fraction tighter.
Is what i used to do if i found one loose, [or less than tight].

There are several of those Yamaha 91608-20010 roll pins on ebay right now.

RT325: good photo of the screw, thanks. My 74 DT175 has that kind of setup.

I agree that the fact the 360 pump still has the pin retaining cage/plate on it makes me think it should use the pin, not the screw. Didn’t know tho with 74 being the newer engines and bikes.

If I'm seeing what I think I'm seeing in that picture, I can't imagine the pin wore out like that.  Maybe a "backyard engineer" modified it to reduce the oiling or something? 

If the "wear" on the pin is wider than the width of the cam surface that contacts the pin, that's likely what happened.