Well as some of you may have noticed from my recent posts here. I am fixing a 1977 dt250. Tore her down and split her open just to put her back together. Now that I've got the bike running and riding I would like to keep the autolube system. However, its either the autolube, timing, or jetting on the carb that caused the bike to get hot and ruin the crank seals last time so I want to make sure it works correctly. The autolube system definitely pumps oil but I am not sure its the right amount and my manual says nothing about it.

So first off I measured the gap between the adjustment plate and the pulley, its too large. I see that I have to adjust the shim to correct it but is this gap being too large going to make it pump more oil or less? I'm honestly fine with it pumping more. Secondly how do I figure out if its pumping the correct amount?  I assume it has something to do with the tach.

Which leads me to my next question. My tach cable is good. it spins freely. when I start the bike however the tach just reads redline. I assume there is some electronic system to push it back in place but I have no idea how this works. I inspected the tach to see if I could just figure it out and gave up but all the wires are definitely plugged in. Any advice on troubleshooting/fixing a tach? 

Thanks again for any input!

There's probably 30 manuals in the Tech Library that have sections on Autolube including the one for your model which includes the specs for your model.

I had checked both the service and owners manuals for my bike and both instances here on the tech library have even less information than the Clymer I have.

PDF pages 9 to 10 of the 77_DT400D_DT250D_manual.pdf  in the Tech Library has the pump shim instructions, bleed instructions and cable adjustment instructions.

PDF page 62 has the pump output specs (per 200 strokes)

The 78_dt400E_DT250E_Manual_supplement.pdf has pretty much the same info but the drawings might be easier to see than pics.

Thank you so much for pointing out page 62. I read everything on page 9 to 10 and it was basically the same as my clymer so I stopped. But 62 has the information I needed.

Now you wouldnt happen to know anything about how the tachometer gauge, not the gear in the engine, functions would you?

Tach is 100% mechanical (if original).  Wires are for lights.

Tach works via a spinning magnet rotating a drum against a calibrated spring. The drum is connected to the needle.

The faster the magnet spins, the greater the magnetic eddy currents produced and more magnetic force to turn the drum.  This allows the drum to pull out the spring further and the needle goes further round the dial.

If the drum or magnet is dirty or rusty, allowing physical contact between the two, it will cause what you describe.

Shaft has to be square on to the magnet piece or it all goes haywire & needle will just go right around. Something like that. Its all magic. Not sure how the needle damping works, maybe some magic grease, but one year think about "72 "73 they must've left the grease stuff on the bench & needle was crazy undamped.