Stihl 048AV - crankcase leak

[30dodgeboy]

I picked up a 048AV along with another Stihl saw a while back for a fair price The seller told me that the 048AV wouldn't idle down so I assumed it likely needed a carb boot and I shelved the saw until I could get to it. I finally started looking at it today and see that there is a section of the crankcase joint (in front near the oil transfer hose) that looked just abnormally clean. The carb boot looked OK, so I sprayed down the crankcase joint with soapy water and blew compressed air gently into the carb impulse hose. Sure enough, bubbles appeared at the clean area of the crankcase joint.

I searched through many 048AV threads here, and it sounds like this a somewhat common issue on this saw model.

My questions (sorry) :

Where is the best place to get the best gaskets to repair this saw?
Are OEM or are aftermarket gaskets better for repairing this issue?
Is sealer a good idea at that location? If so, what type of sealer is most immune to fuel?
What is available for service manual or procedure information?
What about adding thread adhesive, such as blue Loctite 243 to the crankcase half screws?

I've dove pretty deeply into other saws before to make various repairs, but never had to spit the crankcase halves before... Any tips?

Thanks in advance!
Art

 

[ballisticdoughnut]

You can find OEM gaskets on eBay, I haven’t checked but I’d be willing to bet they’re no longer available from Stihl. You can find the 048 service manual here, see the “beg for manuals” thread. I’d follow exactly what the service manual says as far as replacing the crankcase gasket is concerned. There’s a special tool for splitting cases, if you have the means you can make one or the husky “C” case splitting tool may work.

 

[J D]

The original case screws on the earlier 048's were just flat heads & there were issues getting them tight enough. If that's the case I'd replace them with some allen or torx screws.
In similar situations I have had success in the past by loosening surrounding screws, putting vacuum on the case & then applying either regular or whicking locate before re-tightening the screws. I cannot attest to the longevity of this fix as said saws have subsequently had fairly limited use

 

[30dodgeboy]

I had some struggles getting the left-hand threaded clutch hub off, had to resort to heat to get it to cooperate. I used a soft pliers handle between the crank throw (clutch side of course) and crankcase to hold the crank while applying torque. It didn't look like it was loctited on, but it was really super tight (maybe 50-60 ft-lb!?!).
Once I had the clutch hub off, three of the four crankcase half screws were loose. This saw had socket head capscrews (aka 'allen head' screws) holding the halves together. The ones towards the front of the saw were extremely loose, thus the gasket issue.
I drove the two dowels out after verifying they had through-holes big enough, and then separated the crankcase halves with my bare hands. Once apart, half of the gasket was AWAL (red arrow below). Time to order some parts and wait...

 

[ballisticdoughnut]

Gotta be careful heating the clutch. I realize it has to be done in some cases, I’ve done it many times myself. I use a small “crack torch” which gives more precise control of where the heat goes. What I’m getting at is, if your not careful you can ruin the clutch spring(s) pretty easily if they get too hot. Just something to watch out for.

 

[30dodgeboy]

Gotta be careful heating the clutch. I realize it has to be done in some cases, I’ve done it many times myself. I use a small “crack torch” which gives more precise control of where the heat goes. What I’m getting at is, if your not careful you can ruin the clutch spring(s) pretty easily if they get too hot. Just something to watch out for.

I hear ya on the clutch springs, but I had removed the shoes and springs so there was just the center "hub" or 'spider' left on the crankshaft (#19 below).


I used a small butane torch like this to heat only the hub, while monitoring crankshaft temp with my highly technical 'water sizzle test' to ensure the crank stayed below 212 degF.




Thanks for the watchouts, I do appreciate your experience sharing.

 

[Lightning Performance]

Gotta be careful heating the clutch. I realize it has to be done in some cases, I’ve done it many times myself. I use a small “crack torch” which gives more precise control of where the heat goes. What I’m getting at is, if your not careful you can ruin the clutch spring(s) pretty easily if they get too hot. Just something to watch out for.

Smart money takes off the springs and shoes first. A brass hammer on the spider does the trick.

 

[ballisticdoughnut]

Smart money takes off the springs and shoes first. A brass hammer on the spider does the trick.

Some clutches can’t be disassembled on the saw while still threaded onto the crank but yes, if possible that’s another good way of doing it.

 

[Lightning Performance]

Some clutches can’t be disassembled on the saw while still threaded onto the crank but yes, if possible that’s another good way of doing it.

You got to stop working on that stuff

 

[ballisticdoughnut]

You got to stop working on that stuff

Come on now…

 

[30dodgeboy]

You got to stop working on that stuff

Just curious, are you referring to those saws that are only orange instead of those that are orange and white?

 

[Lightning Performance]

Just curious, are you referring to those saws that are only orange instead of those that are orange and white?

Old stuff