Need help with stihl 041 av pressure test problem

[Robert Kugler]

Hi Bob,

Excellent, going with stihl for parts is often the best way forward, though if they are NLA, alternatives from reputable sources can be a good substitute.

It’s good practise to change bearings if you have side loaded them when pressing the crank out, but if you haven’t pressed the crank, they look in good condition, have no play and no abnormal sound then and aren’t rusty, it shouldn’t be an issue.

Note that bearings in their pockets under pressure can sound and feel better than they do when popped out.

I’d personally wait and not try and save an old seal, I understand the impatience side of things as I have been working on an 07 chainsaw for months waiting for parts, but it’s much better to leave the saw apart and get it done properly, than hope a bandaid fix will hold. Maybe start a second project, or clean the rest of the saw parts while you wait, rebuild the carb If necessary etc

Hope this helps

Thanks Tom. That O ring is driving me crazy. I've had in in and out about 5 times and it doesn't seem to seal. The O ring is 7 X 1.5, as stated in the IPL. I picked out the grease and put a touch of fuel mix oil on it to make it slide in, but it wont seal. I know the worm gear is leaking, but it is not leaky enough to account for the rapid pressure drop.
Is that one O ring on the adjuster shaft the pressure seal? I am assuming that the two O rings on the knob are just to hold the adjustment in vibration. I am also testing with the plastic cover off of the cavity where the adjuster shaft is. is that wrong?
Thanks,
Bob
Things will get quiet while I wait for the worm gear. I agree that I should wait for the new part.....

 

[Vintage Engine Repairs]

Hi Bob,

I’m aware that my experience is with an 076 and your saw is the 041. They have similar oilers and the principles behind the oil flow control shaft is similar in principle too, but not identical In design.

These saws have a lower o-ring to maintain pressure and vacuum within the saw and an upper one to stop unwanted movement during the saws operation.

Are there any cracks, debris, damage etc to the seat in which the oil control shaft sits?

Have you fully seated the oil control lever? The bulb at the end of the control lever presses against the oil pump shaft, this requires moderate pressure to compress the spring and for it to seat correctly.

If you take a few pictures of the recess in which the oil control shaft seats and the control shaft itself too, it may show something you might have missed.

It only requires a small amount of lubrication to the o-ring to install the shaft.

Pop a few clear pictures up

Warm regards, Tom

 

[Robert Kugler]

Hi Bob,

I’m aware that my experience is with an 076 and your saw is the 041. They have similar oilers and the principles behind the oil flow control shaft is similar in principle too, but not identical In design.

These saws have a lower o-ring to maintain pressure and vacuum within the saw and an upper one to stop unwanted movement during the saws operation.

Are there any cracks, debris, damage etc to the seat in which the oil control shaft sits?

Have you fully seated the oil control lever? The bulb at the end of the control lever presses against the oil pump shaft, this requires moderate pressure to compress the spring and for it to seat correctly.

If you take a few pictures of the recess in which the oil control shaft seats and the control shaft itself too, it may show something you might have missed.

It only requires a small amount of lubrication to the o-ring to install the shaft.

Pop a few clear pictures up

Warm regards, Tom

Hi Tom,
I will. I am so frustrated with that saw , that I did not touch it yesterday, but I have no intention of giving up.
When I first took the oil adjuster out, there was only a small piece of the old o ring left. I assumed that it was ground up or sitting in the oil pump tunnel (or something). I used a piece of thin copper wire to "fish" for the debris, but found nothing.
I will take some pictures and post them.
I think I will also order an O Ring as a Stihl part. It should not make a difference, but it eliminates a possible source of error.
Thanks Tom,
Bob

 

[Vintage Engine Repairs]

Don’t get too frustrated Bob, you will get the saw working and you’ll learn lots of valuable lessons from one that is challenging you. Once it’s up and running, you’ll forget the hardship and enjoy it.

There is nothing wrong with having a few day’s off working on it to feel refreshed and have a new set of eyes on the saw.

When you are ready try again Shine a good light into the hole and inspect it very carefully, maybe the piece of broken o-ring is still there. Share some photos on here too.

Confirm in the IPL that the 7x1.5 is the correct size for your saw too and use verniers to ensure that they are the size they say they are.

A setback is a setup for a comeback chin up!

 

[Robert Kugler]

Don’t get too frustrated Bob, you will get the saw working and you’ll learn lots of valuable lessons from one that is challenging you. Once it’s up and running, you’ll forget the hardship and enjoy it.

There is nothing wrong with having a few day’s off working on it to feel refreshed and have a new set of eyes on the saw.

When you are ready try again Shine a good light into the hole and inspect it very carefully, maybe the piece of broken o-ring is still there. Share some photos on here too.

Confirm in the IPL that the 7x1.5 is the correct size for your saw too and use verniers to ensure that they are the size they say they are.

A setback is a setup for a comeback chin up!

Hi Tom,
Thanks, I agree with you!
Here are some photos. one is the side with the oil control in all the way, another is a similar view with the control knob in position but not twisted down all the way, another is the knob assembly itself, and the last is a wiew directly down the control knob cavity. My phoyogrsphy is not great, but you can get the idea.
Thanks,
Bob

 

[hotshot]

Lol, looking at IMG_0728.JPG, the new bottom o-ring is in the wrong place & the old worn flat faced one is still there on the control bolt.

You just need to get a dental pick & swap it out.

Go to Ebay & search for “Stihl 041 oil knob“ to see a good pic of one for an example.

https://www.ebay.com/itm/Used-OEM-Stihl-041-Bar-Oil-Adjustment-Knob-WITHOUT-Cir-clip-/274408997193

 

[Vintage Engine Repairs]

As hotshot said

Bin the lower one getting it out with a pick and move your new one down where the lower one currently is and you’ll be good

 

[Robert Kugler]

OOPS ...sorry, the o ring must have slipped before I took the picture.
This is where I have been placing the ring.
It is hard to keep it there when I have been inserting the shaft, but I gig keep it there a few times.
If I gig in that cavity with a dental pick, how easy is it to scratch the cavity walls? I am afraid I will scratch the wall and the o ring wont seal.....

Sincerely,
Clueless in NH....

 

[hotshot]

“If I gig in that cavity with a dental pick, how easy is it to scratch the cavity walls? I am afraid I will scratch the wall and the o ring wont seal.....”

Yep. Gig it like a bullfrog on a creek bank, you won’t hurt anything but the seal.

 

[Vintage Engine Repairs]

That o-ring doesn’t look right to me mate. Something is funny... it seems like it’s not the right size and it’s not sitting properly on the groove of the shaft. The ID of the o-ring should fill the seat of the shaft and it’s not which is probably why it’s being pushed off. It looks too big and too narrow.

Don’t dig in that cavity with a metal pic, why do you want to dig in there?

Edit to update: That looks like the old o-ring still on there underneath?! That’ll never seal and will keep pushing the o-ring out of its groove.

Have you measured the o-rings and cross referenced them with the IPL?

 

[Robert Kugler]

That o-ring doesn’t look right to me mate. Something is funny... it seems like it’s not the right size and it’s not sitting properly on the groove of the shaft. The ID of the o-ring should fill the seat of the shaft and it’s not which is probably why it’s being pushed off. It looks too big and too narrow.

Don’t dig in that cavity with a metal pic, why do you want to dig in there?

Edit to update: That looks like the old o-ring still on there underneath?! That’ll never seal and will keep pushing the o-ring out of its groove.

Have you measured the o-rings and cross referenced them with the IPL?

View attachment 845101

Tom,
I see what you are saying. I will get a vernier and measure the o ring. Meanwhile, I will have to make something wooden to pick out the old ring.
Thanks,
Bob

 

[Robert Kugler]

“If I gig in that cavity with a dental pick, how easy is it to scratch the cavity walls? I am afraid I will scratch the wall and the o ring wont seal.....”

Yep. Gig it like a bullfrog on a creek bank, you won’t hurt anything but the seal.

View attachment 845092

 

[hotshot]

Good luck with that saw, Bob!

 

[Robert Kugler]

Good luck with that saw, Bob!

Thanks Randy.
Bob

 

[Vintage Engine Repairs]

You can use a metal pick to carefully remove the old o-ring, but don’t use the pick to scratch around in the recess that accepts the control shaft.
Warm regards, Tom

 

[Robert Kugler]

You can use a metal pick to carefully remove the old o-ring, but don’t use the pick to scratch around in the recess that accepts the control shaft.
Warm regards, Tom

Hi Tom,
yeah....the wooden dowel did nothing. I guess Randy called it.
The old O Rung is at the bottom of the shaft and is stuck there.
Someone thought I should put tape around a 1/4 inch drill bit and use the bit to hand gring the o ring loose. The tape on the bit would protect the shaft walls. I tried the pick and the o ring will not come loose.
The fact that the o ring is stuck at the bottom of the shaft makes me wonder how important it is to remove it. The oil control knob shaft will screw down to the metal bottom of the shaft, and the sealing surface for the o ring is near the top of the shaft, so even if the old o ring is there, what does it matter?
The part of the knob shaft that contacts the oil pump is about 1/4 way up the shaft, so the old o ring does not interfere with that either.
I guess .....why worry??
I got a 7 X 2 mm to try on the knob shaft, and it is definitely too big, so that 7 X 1.5 that I ordered must be the correct o ring (it is labelled 7 X 1.5 in the IPL).
I'll go after the stuck o ring, but i don't know if it will fix the problem.....the problem may be pilot error

Bob

 

[Vintage Engine Repairs]

Hi Tom,
yeah....the wooden dowel did nothing. I guess Randy called it.
The old O Rung is at the bottom of the shaft and is stuck there.
Someone thought I should put tape around a 1/4 inch drill bit and use the bit to hand gring the o ring loose. The tape on the bit would protect the shaft walls. I tried the pick and the o ring will not come loose.
The fact that the o ring is stuck at the bottom of the shaft makes me wonder how important it is to remove it. The oil control knob shaft will screw down to the metal bottom of the shaft, and the sealing surface for the o ring is near the top of the shaft, so even if the old o ring is there, what does it matter?
The part of the knob shaft that contacts the oil pump is about 1/4 way up the shaft, so the old o ring does not interfere with that either.
I guess .....why worry??
I got a 7 X 2 mm to try on the knob shaft, and it is definitely too big, so that 7 X 1.5 that I ordered must be the correct o ring (it is labelled 7 X 1.5 in the IPL).
I'll go after the stuck o ring, but i don't know if it will fix the problem.....the problem may be pilot error

Bob

Don’t use a drill, tape won’t protect anything. What o-ring is inside the female area that accepts the shaft?

The o-ring I’m talking about is the the old one on the control shaft that I showed you before. The o-ring may be stiff like plastic now so it will take more effort to remove, it’s essential it’s not there for proper sealing from the new one, do the job properly . Otherwise you will keep getting the leak you are.

 

[Robert Kugler]

Don’t use a drill, tape won’t protect anything. What o-ring is inside the female area that accepts the shaft?

The o-ring I’m talking about is the the old one on the control shaft that I showed you before. The o-ring may be stiff like plastic now so it will take more effort to remove, it’s essential it’s not there for proper sealing from the new one, do the job properly . Otherwise you will keep getting the leak you are.

Hi Tom,
I attached an illustration (out of scale), to show what I mean.
To start, I am not sure that there is even an O ring down there; but if nothing is there, then I don't know where the old one went. As I mentioned, I only got a small piece when I took the control shaft out, and the shaft has not been removed in 40 years while I was using or storing the saw. It used to work great, but after 15 years of storage it would not start, which got me here.
When I went down the tunnel with a dental pick, I thought that I could feel something spongy like an old O ring, but it may have been the end of the dental pick flexing.
When I went in there just now, the bottom of the tunnel felt smooth, except for the threaded hole at the bottom.
Now I am really confused .
The attached illustration shows the control shaft inserted in its tunnel, and the blue dots in the control shaft groove are the new O ring.
The blue dots at the bottom of the tunnel are the (maybe) stuck O ring.
The upper walls of the tunnel are smooth (as sensed with a Q Tip); so the new o ring should seal regardless of the debris at the bottom.
The original photo of the tunnel (cavity) was not real great, so I wonder if there is bottom discoloration instead of an o ring.
Anyway, I think I must be missing something...do you have any thoughts?
I have also attached a picture of the dental pick.
Thanks,
Bob

 

[PogoInTheWoods]

Wow. Outstanding thread on the subtle (and not so subtle) aspects of pressure testing and troubleshooting an 041 oil pump! Great stuff, guys..., especially the encouragement factor.

My only comment would be that I hope the saw was pressurized prior to (and while) being submerged to eliminate the possibility of water migration into the case. Even though the main leak would currently appear to be via the oil system and would not likely provide a very convenient path to the crankcase, that doesn't necessarily mean the oil seals couldn't still allow water into the bearings/case (or pass a vacuum test) even though they've passed a couple of bubble pressure tests so far. That may change once any larger leak sources have been fixed. And once the saw seems to have passed all the air leak tests using pressure, vacuum testing is a must to ensure the absolute integrity of all components subject to air leaks, especially the oil seals.

Good luck with it!

 

[Vintage Engine Repairs]

Get the old o-ring off the control shaft and put it back together Bob. The missing piece may have fallen down that threaded area. Not ideal, but unless you split the cases you won’t find it.