044 PTO crank and oil spacer bush seal question

[MattG]

Morning Folks,

I've been slowly dismantling a complete(ish) but non runner 044. I've got all sorts of ideas for it project wise (e.g. I have a 12mm wrist pin crank to swap in, then perhaps convert to 460 hybrid). However as I strip it I'm obviously uncovering what's wrong with it etc. Well the piston is well toasted and has start of a hole forming on it's crown. So I wanted to know why, the carb settings (1 turn out on both) seemed fine, so I go leak hunting in my usual way, off with the f/w and the clutch, and block off the exhaust and inlet. Needless to say the mityvac won't hold any +ve pressure whatsoever. I can already hear the leak, and it's on the PTO side:



Above is a shot after I'd started to investigate matters. I'm not sure whether you should +ve pressure test a 044 in this state, since I'm now curious as to whether the clutch back washer is needed to press that bush further into the engine. However, that's how I usually test, since it gives you good visibility of the problems.

Anyway I could see/hear the air leaking from here, especially between the bush and the shaft itself. However after removal of the bush it looks as if the crank seal itself aint in great shape either.

So now I'm curious how does the whole thing work? Is the bush supposed to spin with the crank, i.e. rotate against the seal? The wear pattern on the bush suggests this to be more likely:




than it staying fixed against the seal inner lips and the crank spinning within it.

So can someone please explain this to me, i.e. what edge(s) must be sealed, what spins during operation and what shouldn't, etc. etc. ?

 

[Steve670]

Clutch needs to be on there when pressure and vacuum testing.

 

[MattG]

My next query is that of the mysterious O ring for the spacer bush inside groove:



which according to Stihl, sometimes is there, for example in the service manual:

but mysteriously is not mentioned in the IPL!


or on



I know that loads of you have rebuilt these engines, and know far more about them than me. So can some people give me answers, like what parts spin etc., whether the inner part of the bush against the shaft should seal etc., and the mystery of the O ring.

 

[MattG]

Clutch needs to be on there when pressure and vacuum testing.

Thanks Steve, that's bad design in my book, since it makes location of leak much harder!

What's your views on the deal about the "missing o-ring" ?

 

[MattG]

@Canadian farm boy
Hey Fella,
I know that you've rebuilt these saws loads, what's your views on how they seal up on the PTO side?

 

[Canadian farm boy]

The mystery oring isn't needed. Stihl only used them on the earlier 044 saws.
The bearing spacer rides against the inner bearing race. It's held in place with the clutch. When vac/pressure testing remove the oil pump drive gear and the oil pump. Slip the large flat washer and clutch back on and tighten it down as you normally would.
The bearing spacer spins with the crank.

 

[Canadian farm boy]

If you have removed the bearing spacer and the crank seal is still in place caution must be used when reinstalling the spacer. Watch that you don't accidentally roll the seal lip when you push the spacer back on.

 

[cus_deluxe]

Hey mike, do you use any type of sealer between the bushing and the crank?

 

[Canadian farm boy]

Hey mike, do you use any type of sealer between the bushing and the crank?

Nope. IMO it's not needed.
I just lube em up where the seal rides when I install them. When I push the bearing spacer past the seal lip I'll spin it between my fingers. This helps prevent the seal lip from getting rolled over.

 

[Brewz]

As said the clutch clamps the spacer up against the bearing inner ring and it becomes part of the shaft.

BUT

If you use one of the after market bearings, the inner ring is 1mm narrower, so the spacer hits the crank before it seats on the inner bearing sleve.
This causes the spacer to crack, fail, jam the worm gear etc etc.

I have used the after market bearings on all other saws they fit (024, 026, 046 etc) and they work fine, but not on an 044 with the spacer.

I thing the after market 044 cranks may actually be machined allow them to work.

Just an "off the side" bit of info

 

[cus_deluxe]

Nope. IMO it's not needed.
I just lube em up where the seal rides when I install them. When I push the bearing spacer past the seal lip I'll spin it between my fingers. This helps prevent the seal lip from getting rolled over.

Thanks, good to know!

 

[MattG]

@Canadian farm boy
Thanks for your tips. I'd sorta guessed that the o ring must be unnecessary, as it's not on 440 IPL either. And yeah the design must be for it ride against the bearing inner.

If you have removed the bearing spacer and the crank seal is still in place caution must be used when reinstalling the spacer. Watch that you don't accidentally roll the seal lip when you push the spacer back on.

To be fair I'm gonna change the seal (and the rest of the gaskets/seals etc.) in due course.

So what procedure do you use for reassembly (the manual wasn't too clear IMO) of the seal and the bush?

My guess is that once you've got the crank and casing back together....

1. push the bush spacer on the shaft first?
2. then lube the inner seal lips and press that on over the bushing?

 

[MattG]

As said the clutch clamps the spacer up against the bearing inner ring and it becomes part of the shaft.

Cheers Brewz, I've just checked the IPL and yeah that looks like the intended situation. I guess one other detail to bear in mind is (on reassembly) to get the worm drive piece lubed so that it's good to allow the shaft to rotate within at idle, when clutch aint engaged.

 

[Brewz]

The worm gear should be just a bit shorter than the top of the spacer so the clutch does not clamp it.

I always hammer the clutch tight with a rattle gun and make sire I still have free 360* rotation of the worm gear before I go any further.
If the work gear sticks, something is wrong.

 

[mdavlee]

If the spacer isn't too expensive replace it. I chased an air leak on a 2165 for weeks and it ended up being the spacer to seal.

 

[Canadian farm boy]

@Canadian farm boy


My guess is that once you've got the crank and casing back together....

1. push the bush spacer on the shaft first?
2. then lube the inner seal lips and press that on over the bushing?

You got it. This is usually how I do it.

 

[Brewz]

If the spacer isn't too expensive replace it. I chased an air leak on a 2165 for weeks and it ended up being the spacer to seal.

New OEM spacer cost me $87 here.
Aftermarket one that does same job was $3

 

[mdavlee]

WOW

 

[MattG]

If the spacer isn't too expensive replace it. I chased an air leak on a 2165 for weeks and it ended up being the spacer to seal.

Yeah, that's what I'll reckon I'll do. This 044 is gonna be a slow project for me, so I'm good for paying the money to get it right.

Nightmare price for @Brewz though. I just looked up the price for us over here and I can get OEM for 20 quid inc. tax. A lot of money for a machined out piece of metal, but still I guess I'll pay up.

Just a shame that I didn't stop and think before I tested her, then I'd have got the clutch back on etc. before. TBH she didn't hold ANY pressure at all so I'm guess that the seal was already blown.

I'm gonna spend more time on it tomorrow, so I might try temporarily glueing things up with a bit of sealant, lobbing the clutch back and retesting it that way. I.e. see if any other leaks show. Because what I do know is that there must be damn good reason why the piston is fried! Whatever - I'm reckoning that PTO seal is history - I'm sure it's lips looked flat to me yesterday - will try to get some piccies up here tomorrow...

 

[BuckthornBonnie]

Nuts... I just put one together and installed the seal first, then the spacer bushing. Doesn't it make sense that the spacer can be removed from the seal area and reinstalled?