Stihl 051 AVL 4. - The missing pieces

Oil pump bushing

The 051’s oil pump has two small bushings (number 10 on the diagram below) that holds the the rubber seal in place and this is where the oil is pumped through. When I removed the old rubber ring one of those bushings fell off, and disappeared in the black hole under the bench. This is such a small part that it’s basically impossible to find it on the shop floor. Googling the item number you could buy this, but paying the shipping from abroad, and waiting for it to arrive is not really reasonable when I can remake it.

I don’t remember the exact sizes, but it’s fairly simple, a 2.5 mm inner diameter I think, roughly 5 mmm lenght, with a shoulder in the middle. The larger OD fits in the oil pump itself, and the smaller one fits in the rubber ring.

It looks good to me!

Chain tensioner

I already ordered all the parts I needed when realized that one of them is missing. The old tensioner has seen better days, the screw slightly bent, the threads quite worn just like the nut, so I thought it’s worth replacing it.

Same thing as with the bushing, it’s just cheaper and easier to make a new one.

I made the nut from I think a piece of 12 mm round bar, after roughing out the ODs I parted off, it turned out a bit too long, but it’s okay, just machined off a mill or two. Then scribed roughly where the screw should be, and tapped an M6 thread in it, nothing special.

The screw has a bit more to it, but it isn’t complicated either. The important things are the overall length, the shoulders that keep it from falling out, and the unthreaded part that also fits in the housing.

I’m happy with how this turned out, well except that I couldn’t cut the head of the screw nicely with the angle grinder, but hey, it works.