Chainsaw Repair

As I noted in the "Wanted" section, I am working on the oiler for my 371xp.
I got the clutch off with 660magnum's inspiration to make my own tool.
Next is the propeller looking part, the drive wheel.
The 371 workshop manual says to unscrew this and remove.
Well mine did not need to be unscrewed.  I was able to just lift it off.
It does not screw on or off.  There are good threads on the outside of the drive wheel, but do not see what it is suppose to screw on/off of.
Also, I am not finding the oil pump washer, PN 503 23 00-59.

There are three parts that are needed for the pump drive. The washer you noted used to keep the pump drive from eating up the seal, 503521501 the pump piston, the drive wheel engages the splines on the piston, the crank shaft bushing 503779101 this is what the pump drive rides on, there should be a very thin o-ring  beneath this 503263019, it seals the crank going through the inner race of the bearing.

Have a look at your pump drive to see if perhaps the bushing came off with the pump drive.

So here is the assembly order, o-ring on the crank against the inner race. Sleeve over the crankshaft, large end into the seal. Then the washer over the bushing against the seal. Then the pump, then the pump drive spins down engaging the splines on the pump piston.

I suspect the problem to be a severely worn piston shaft or the drive is going past the pump piston because of the missing washer. Post a set of pictures of your parts.

Your third picture clearly shows the sleeve in its' proper position, the sleeve just slips inside the seal, underneath it is the o-ring mentioned in my earlier post. The washer you are missing slips down over the sleeve and rests against the seal. It is there to keep the rotating pump drive from chewing up the outer lip of the seal and to keep the drive fully engaged with the pump piston. On the 365/372 series of saws the oil pump is driven off the clutch drum not the crank shaft. E.g. the pump drive just spins freely on the bushing when the clutch engages.

In your second picture you can see the pump shaft with splines that engage the outer threads on the plastic pump drive wheel. If the washer you are missing is not there the pump drive wheel will sometimes go in too far and not engage the splines enough to drive the pump efficiently.

Lastly take your pump drive and lay it across the notches in your clutch drum to make sure that the ears on the drive protrude a tiny amount past the notches in the drum. Sometimes people put the drum on without engaging the drive in the clutch drum causing premature wear on the drive.

Sorry, I missed one of your questions. You should have to unscrew the pump drive from the shaft. What you are really doing is disengaging the pump drive from the pump shaft. The threads of the pump drive should be centered over the pump shaft equidistant from either end of the threads on the drive wheel.

Yes that is also a possibility, also the drive wheel threads are supposed to meet the pump shaft at the 12 o'clock position. Too much either way toward 11 or 1 o'clock will not drive the pump correctly and may cause the drive to slip past the pump shaft at high RPMs, just where you need the most oil.

Unfortunately I do not think you are going to find the washer any where but Husqvarna, if you have to order it you might as well order a new drive wheel as well.

The missing washer is P# 503 23 00-59 is $3.40.
The pump drive gear is P# 503 75 61-02 is $13.61.