The International Cessna 170 Association

Thanks again Bruce.

I have a primer which has a threaded nut and plunger shaft instead of the slotted nut and key to keep it in. Is this, I hope, even original, and if so, use the same o-rings. I haven't yet attempted disassembly except for removal of the nut, which does not allow for removal of the plunger. It's on a '50 A-model

Scott I've never seen a primer like you describe. Doesn't mean there aren't any. Are you sure there is no slot for a pin to fit through the nut.

Bruce, no there's no pin or slot. It's a totally different style. The nut, which is not knurled, it's a hex nut, has internal theads that threads on the shaft screw into. The threads are quite coarse, probably 8 or 10 pitch, though there is only a couple theads, are just below/behind the knob. I'll have to try and figure out how to attach a pic.

Scott if you can figure it out you can send the picture to my email address and I can post it.

Here are the pictures of Scotts primer. Can anyone identify it. how does it come apart and what if any o-rings does it have?

Wow, never seen one of those. What holds it closed? I can envision an o-ring or something in the nut part that holds the shaft just below the knob but a normal aviation primer has a needle on the end of the shaft that seats to close off the fuel supply when closed. Is it even for an airplane?
Very interesting.

Dave if you look close just behind the knob you'll see the threads Scott mentioned in his previous posts that thread into the chrome nut at the panel.

Oh I thought those were rings. Still, pretty weird.

If you will cross refererance that An6227-7 to a MS29513-012 you will probably solve a lot of your problem. The An6227 material is for Mil 5606 hyd fluid applications, whereas the MS29513 is for hydrocarbon fuel applications. What is probably happening is those 6227 orings are swelling after a time and binding up your primers. For a dollar or so you could experiment and throw one of each in some 100 LL and observe which one swells the most. If you have a Aviall catalog it gives a list of o-rings and what their application is. Also some of the primers like Bruce pictured have two o-rings on the plunger FWIW Brian

Guess I have a profound grasp of the obvious when it comes to counting o-rings

It's been awhile, but the weather finally let us go flying yesterday. I earlier had replaced both O-rings and used DC-4 on them. Had some "peanut butter" in the tube, but got it cleaned out. It's like having a new primer in the plane. My primer, like Scott's, had a nut (11/16") too, but with a slot for the locking pin to fit in. Thanks for all the help gentlemen

Ah, it's the little things in life that are the pleasures.

Went out to the hanger over my lunch hour and replaced the 2 O-rings in my primer. It was beyond giving my wife trouble pulling it - even I found it tough.

Now it's soooooo easy to use. Becky will be pleased!

Once again the forum comes through.

My primer gets difficult to pull every now and then. I just follow George's example and apply a little WD-40. Primer works well for months.