O&R: shaft seals for 3/4HP .85HP & 1HP engines (including 13A & 13B)

[Webhead 95]

So what do you guys think of the correct size "o" ring for an output shaft seal? I'm about out of originals, still good on the crank side.

[Wallfish 698]

I don't see any problem with using O rings. Particularly on that side since the seal sits deep in the groove of the induction sector.

[tackdriver56 2]

I'm interested in the original question: SIZE: shaft diameter, bore diameter, seal cross section. It's possible that commercial U-ring seals might be available.  I'm also wondering about the material: is BUNA-N (Nitrile Rubber) the correct material for these engine seals? Thanks!

[factory 487]

The O-rings I bought for the cylinder are made from Nitrile rubber, which is generally resistant to oils & fuels, the disposable gloves I use at work are also made from Nitrile rubber for the same reason.

According to wikipedia the higher the oil resistance, the less flexible it is.

http://en.wikipedia.org/wiki/Nitrile_rubber

 

The shaft diameters are different for early & late engines, I haven't actually changed any of these seals yet. But I intend to find out what is available locally, as I have an early engine with all the seals & gaskets missing.

 

David

[tackdriver56 2]

Thanks. I guess I'll have to tear it down to determine the actual sizes.

[CNew 404]

Has anyone successfully replaced this little rubber shaft seal (flywheel side) with an O-ring?

Edited June 1, 2019 by CNew
Missing letter

[factory 487]

Not tried to yet, but it shouldn't be too hard to find an O-ring with the correct diameter and thickness, maybe harder over here as we mostly use metric stuff.

By the way I have never found anywhere selling seals anything like those originally used.

 

David

[CNew 404]

I may have to give an o-ring a try.  What about the shaft seal just behind this one that is inside the housing in the groove, can an o-ring be used successfully there?

[Wallfish 698]

Try searching around the net for U cup seals like this

https://www.mcmaster.com/cup-seals

 

[CNew 404]

I haven’t been successful yet finding this type of seal in the unusual sizes for the O&R but will keep hunting, that’s part of the fun!

[CNew 404]

I finally got this engine all put back together yesterday.  I didn’t attempt to replace any of the shaft seals with o-rings just yet.  I thought I would first see if the old seals had a little life left in them. Well, I got the engine to run for 1-2 seconds at a time, basically it will fire off the little bit of gas from priming the carb. Does this sound indicative of a seal leak or a fuel problem? I completely rebuilt the carb and cleaned the fuel tank and also added an in-line fuel filter (I do that on pretty much all my engines now) so I think the fuel system is working properly.  By the way, the little “Crap Trap filters by Sullivan No 187 are great). 

 

As soon as I got the engine all back together I remembered the engine/shaft seal leak tests from previous threads. I was kicking myself for forgetting to try those techniques before buttening it all up.  But, I guess I’ll get a second chance now

On 6/4/2019 at 5:16 AM, Wallfish said:

Try searching around the net for U cup seals like this

https://www.mcmaster.com/cup-seals

 

If an alternative replacement U-cup seal in this particular weird size range for O&R continues to be non-existent, what are your thoughts on a X-profile o-ring? I was wondering if this style o-ring might offer sort of an in-between solution of a U-cup and a standard O-ring.

 

I haven’t ever actually pulled one of the induction shaft seals out of the little groove.  Is it also a U-cup style or something completely different?  It doesn’t look like a U-cup to me but without actually getting it out it’s hard to tell. Does anyone have a NOS seal that can post some close up photos?  Given their scarcity I don’t want to accidentally damage one pulling it out just to study it

Edited June 16, 2019 by CNew
Forgot letter

[Wallfish 698]

13 minutes ago, CNew said:

 Is it also a U-cup style or something completely different?

Check out the engine rebuild thread, there's a pic of that seal. It's also a U cup

[CNew 404]

Just looked at the rebuild thread again, thanks!

 

Hmmm, you’d think someone would make little seals like this for chainsaws or something... more searching I guess. I still wonder if a X-profile o-ring might be an option. I don’t know enough about how the seal functions but I’m guessing that since it’s a pressurized system it’s best to have the U-cup rather than a more compressive type seal like an o-ring or the x-profile o-ring.

[Wallfish 698]

18 minutes ago, CNew said:

On 6/4/2019 at 6:16 AM, Wallfish said:

 

If an alternative replacement U-cup seal in this particular weird size range for O&R continues to be non-existent

Post the size of the seal for easier searching. That X style appears like it would be better than a simple O ring but...

It's my thought the U cup style was used because the case pressure will tighten the seal from that case pressure pushing inside the U of the cup

[CNew 404]

I’m with you, the U cup is probably needed for properly managing the case pressure, shaft friction, etc.  The o-ring approach might work for very short runs but would likely wear out fast or cause other problems unless you could get just the right balance of exact dimensions so as not to be too compressive on the shaft and against the inner wall of the groove.

[CNew 404]

I found a possible source for small U cup seals so I took a gamble and ordered a couple different sizes. I’ll let you know once they arrive and I have a chance to see if they fit.

[CNew 404]

Well the small U-cup seals that I ordered arrived and I was initially excited as they looked like they were going to be perfect solution but unfortunately they were just slightly out of spec for ID.  So close...  back to researching.

[factory 487]

Do the seals fit any of the different sized shafts found on O&R engines? They did use four different seals as you may already know.

 

David

[CNew 404]

David,

I did not realize there are different size shafts. That’s good to know, perhaps they might fit one of them. I’ll have to keep these on hand and check next time I have an engine opened up. Do you know the OD measurements on the different size shafts?

[factory 487]

I must admit I've not measured all the sizes, but it's something I found out a long time ago, they beefed up the main crankshaft bearings too.

The picture below was taken during my Petro Chug-A-Pump restoration, when I very quickly realised the parts incompatibility between early & later engines.

 

 

David

[CNew 404]

Very interesting.  I was going to return these seals but I think I’ll keep them and see if I run into any of these larger shafts.

[factory 487]

I should probably point out that the shafts in the picture are from a 3/4HP engine (top) and a 1HP engine (lower), I've also found a mention in one of the service bulletins that Series 13 engines made after June 1972 have some none replaceable seals.

 

David

[CNew 404]

Interesting. Not sure I’ve come across an engine yet that has no replaceable seals. I wonder what they use instead. I just opened up another engine so I’ll tank some measurements and see if any of these new seal candidates will fit. The were so very close to being a fit on the last shaft I tried.

[factory 487]

The very late seals are attached to a steel ring, the flywheel side one can apparently be pressed out & replaced (if you could find replacements of course), but the reed valve one cannot be removed as the bearing ring in front of it prevents removal.

 

David

[HeadExam 1,783]

9 hours ago, CNew said:

 

HeadExam,

   Thank you for the insights. That’s kind of what I was afraid of. I’ll have to look into the leak tester you referenced. Is that the same thing as the Mityvac 8500?

 

You also have me curious regarding replacement seals.  I’ve recently been hunting and trialing various seal options for the Compact engines.  Have you ever looked into shaft seal alternatives for the 13A and 13B engines?  I found a source that had some small U-cup seals that were very close but not quite right. I’m still trying to determine if I can get them to work.

 

Clint

If you can use a micrometer and give me the sizes of the seals and type/number of lips, I may be able to cross reference it to a stock seal.