Stihl 041 PTO Seal Problem

[Bob95065]

I have a 041 Super that I built out of a box of parts I got in a Craigslist offer. The saw ran great then developed an air leak. I put it down for a few months and got a chance to look at it today.

The seal on the clutch side was chewed up and torn. It worked its way out and hit the clutch. I put a new seal in it and it slid in easily. I'm afraid it will do the same thing as the first seal.

I checked ebay and only see rubber seals like the one I installed. I hoped I could find a metal cased seal that would seat securely in the bore.

Do you put sealer on the outside of the seals on a 041? I'm thinking about using Dirko so it doesn't move. I usually don't put anything on the outside of seals when I install them.

Thanks,

Bob

 

[Jasonrkba]

I sometimes use motoseal. Locktite or motoseal on the metal ones.

 

[Vintage Engine Repairs]

I use Dirko HT red on every seal. You could always try peening the seal in place too, but if you do, again use a sealant.

 

[Patrick1903]

I have a 041 Super that I built out of a box of parts I got in a Craigslist offer. The saw ran great then developed an air leak. I put it down for a few months and got a chance to look at it today.

The seal on the clutch side was chewed up and torn. It worked its way out and hit the clutch. I put a new seal in it and it slid in easily. I'm afraid it will do the same thing as the first seal.

I checked ebay and only see rubber seals like the one I installed. I hoped I could find a metal cased seal that would seat securely in the bore.

Do you put sealer on the outside of the seals on a 041? I'm thinking about using Dirko so it doesn't move. I usually don't put anything on the outside of seals when I install them.

Thanks,

Bob

Hi Bob. I was working on an 041FB a year or two ago and I seem to remember that the worm gear for the oiler pushed into the crankcase. I can’t recall how the seal and oiler were involved , it’s all. A bit fuzzy. I’m just wondering if somehow the worm gear could have affected your seal? here’s the worm gear in the IPL. I recall when the starter was pulled the worm gear would push out from crankcase pressure.

 

[stihltech]

I always prefer the rubber covered seals. Best if installed dry on the outside. New issue to me that you have. I would check the bearing and worm for play. The seal on the worm was an leak prone area. But then it is a 40 year old saw. Still see them occasionally. Actually put together a nice super a few years ago. Now if I can find the owner?

 

[wildwes]

That worm gear seal can cause a little bit of a leak. It's pretty cheap to replace the rubber seal inside of it, and not hard to do. I can't remember the part number or dimensions of just the seal, but I think the last one I bought was around $3 on ebay.

 

[Bob95065]

Hi Bob. I was working on an 041FB a year or two ago and I seem to remember that the worm gear for the oiler pushed into the crankcase. I can’t recall how the seal and oiler were involved , it’s all. A bit fuzzy. I’m just wondering if somehow the worm gear could have affected your seal? here’s the worm gear in the IPL. I recall when the starter was pulled the worm gear would push out from crankcase pressure.

That design is somewhat complicated. The work gear does push into the crankcase. The ID of the seal contacts the work gear housing and seals. There is an additional seal on the ID of the work gear that is getting hard to find.

There is a small pin that connects the worm gear and clutch. That pin drives the worm gear when the clutch rotates. There is a washer between the work gear and clutch too. The washer and clutch rest on a step in the crankshaft. The washer and clutch stop the work gear from leaving the crankcase when it is under pressure.

In the IPL screenshot you posted you can see that the worm gear is cut into the inner portion of part 14 and there is a smooth portion on the outboard side. That smooth portion rides on the seal.

After work last night I removed the flywheel side seal and cleand bothe bores. I used Dirko to bond the seals in the crankcase halves. Tonight I'll pressure test the saw and put it back together. I hope those seals don't have problems because they will be hard to remove.

 

[Patrick1903]

Here’s a good post and thread about 041 air leaks for you or anyone else that stumbles across this thread.

Post in thread '041 Problem and Theory'
https://www.arboristsite.com/threads/041-problem-and-theory.261143/post-4908158

 

[Bob95065]

I just put the saw back together and the seals held. The small seal, #15 in the picture above has a small leak. That one looks hard to find

 

[wildwes]

I just put the saw back together and the seals held. The small seal, #15 in the picture above has a small leak. That one looks hard to find

I found the last one I bought on ebay, it was around $3. It is pretty easy to change.

 

[Bob95065]

The part # for the 041 seal is 9643 003 1160, dimensions 12x16x3. It is scarce although there are some expensive options on eBay.

Part # 9643 950 1160 is called out for the 028, 030, 045 saws and has the same 12x16x3 dimensions. It is easier to find. Does anyone know if these seals are interchangeable or what the difference is between them? The dimensions are the same.

 

[Bob95065]

I picked up 9643 950 1160 on my way home from work last night. I'll install it tomorrow morning. I plan on doing a pressure/vacuum test afterwards to be sure the crankcase is sealed. I'll report results when it is complete.