088 crank seal failure

[Ax-man]

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Hello all, it has been awhile for me since I have contributed to the chainsaw threads . I thought I would share some info on an 088 I was asked to work on because 088's don't get much attention here unless your a logger, serious tree service owner, or do serious milling. I put some pics in the thread for added interest as this model is a little more complicated to me to work on verses other big Stihl's I have worked on. This isn't my saw although I do own an 088 but have never had to work on it except change air filter, sprockets , bar and chain so my experience under the outside covers was very limited when it came to an 88 and was a little reluctant to work on it for fear of messing it up but decided to try .

Here comes the story , bear with me.

This was my second encounter with this saw for the same owner and it has had a hard life, run hard and put up wet. The first time I worked on the saw was for an oiler not working. The guys running the saw would dump bar oil on the chain and it also was hard to start and the owner asked me to just look at it and see what it needed. A bad decomp valve was the culprit for not starting good, the clutch side was an abortion , a very badly worn sprocket and messed up oiler gears. The owner got new parts except for the plastic oiler gear under the clutch which I needed instead of just that spring arm that turns the gear via the notch in the clutch sprocket. I was able to get the new and used parts to work and get the saw starting better and the oiler working and the owner was very happy.

Now the saw is back on my bench for second time only this time we have a no start problem unless you primed it heavy choked it and then it would start, lean out and die. I thought it would be a simple carb cleaning easy fix to get the saw running . The logical assumption was it wasn't getting fuel but this wasn't the case that darn used plastic oiler gear under the clutch came back to haunt me. That gear in the first picture wasn't as rough looking when I put it back together the first time but degraded to the point it tore the crank seal apart and caused the saw not to be able to create vacuum to pull fuel out of the carb hence no starting without a prime.

I am not putting that saw back together without a new gear like I wanted in the first place . It looks like it got hot at some point and just kept digging into the crank seal . If anyone has a different theory I would appreciate it because I am sure I didn't put any parts back together wrong the first time unless they were wrong to start with. After removing that gear to look at the seal it was sitting in it's housing(?) or seat a little crooked or raised on one side and not sitting level . The saw is old and I can't help but think that maybe with the age of the saw it got tired and the saws compression pushed it out just enough to get chewed up by that oiler gear.

That is the jist of my saw problems and if anyone has other thoughts feel free to speak up.

There is more to this story so if your not bored by reading this long post, keep reading. I'll try to keep it brief. I am only putting this in here in case some one needs to get a peak inside an 88. They are just different to work on . This is by no means a 088 fix it tutorial

First is the carb . I had that big Tilly carb with it's limiter caps out twice to give it a good cleaning and inspection. I was sure surprised to see limiter caps on this old of a saw. The first time I had to really study it to see how to remove the carb. It is a little tricky to remove it from the air box. Stihl over engineered this set-up to me but who am I to say what is good and what is not a good idea. The saw has two throttle linkages , one coming from the trigger , the other from the choke lever up to the throttle plate in the carb and a third lever for the choke plate . The handle cover comes off first to expose the trigger to remove the first linkage, next the screw on the bottom right in the pic comes out to remove the keeper holding the choke lever in place. Then the choke lever has to come up and out of it's retainer, slide it to the left to slide off the choke rod and the second throttle rod lever off the choke lever. Also undo fuel line, pulse line and that air box plug that goes over idle and Hand L screws. Clear as mud , the pics kind of show what I am talking about if you look at them close. I am probably not explaining this all that good but it isn't that hard as long as you study things and not get crazy by forcing pieces apart or forcing them back together. When putting all this back together you do things in reverse but have to play with that ignition ground strap that kills the spark making sure it is in it's proper place on the choke lever . Practice makes perfect and the second time was much easier.

OK , one more item, the exhaust, again I never ran into a set-up like this one . The muffler is held in place with two c clips that go onto the muffler itself and the cylinder block and held in place with that heavy wire retainer along with two bolts at the front of muffler that screw into the crankcase . Again the pics show what I am talking about.

I am not crazy about this feature either. The only reason I removed the muffler was to look at the piston to see if had a bad ring or something out of the ordinary as to why the saw wouldn't start. I also don't like this arrangement because I am at a loss as to how to get a good seal around the exhaust port to do a pressure vac test . Blocking the carb is easy enough to do but sealing the exhaust port is not so easy. Any ideas would be helpful. It is not like doing most saws by unbolting the muffler ,slide a rubber gasket between the exhaust port and muffler and retighten the muffler to seal the exhaust port. I can't find any kind of rubber gasket material that is thin enough to allow those c clips to be put back in place to seal the exhaust port . I would like to do some kind pressure vac test when the new crank seal goes in but it looks like I'll have to wing it on this one. Any help with this would be useful.

Ok , end of story . I hope this has been some what helpful if you ever need to work on an 88 because I am leaving a lot out and hasn't been too boring.

Edit, I did it again by playing around with the edit function and got the pics in the wrong order they should be at the end of the post verses the beginning . I am going to leave it as is . Sorry

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[Ax-man]

Since I have been hanging around the chainsaw forum I might as well reply to my own thread .

Running this 88 with the oiler not working and old parts caught up with the owner of this saw. I put a new crank seal in the saw along with a new pump gear for the oiler. Didn't work , the crank case wouldn't seat the new seal , it was moving around with the crank shaft it was so loose. The saw did run but was all over the place with erratic idle and crappy acceleration. So I call the Stihl dealer to see if by chance we had the wrong seal which we didn't and what else we could do . The only thing we could come up with was to use some of that Dirko sealant that is used to seal a crankcase on a clam shell engines . I had my doubts about this one but decided to see if it would work because I never put any sealant around any crankcase seal that I have installed in a saw. After putting in another new seal with the sealant and letting it dry over night I put the saw back together and it ran OK for a short time but wasn't long before it started going backwards with the same problems. I took the saw back apart and sure enough it had blown all that sealant out and was loose in it's race or seat .

I took the saw out to the Stihl dealer to show them what was going on instead of trying to discuss this over the phone. They couldn't believe it when they saw it , they had never seen anything like it. The only way to fix it was to split the crankcase and remove that bad half of the crankcase with another one. I told the owner of the saw about this problem but I wasn't about to get this involved with that saw mainly because I didn't have the right tools to do such a delicate operation on an old saw like this and the outcome may be like throwing good money away because he wanted to use his old parts .

The only other thing to do would be to find a good crankcase and then switch all his old parts over to it and hope for the best . That is where we at as of today. I hope he loses interest in the saw because after awhile I can consider it abandoned and make it my saw I would buy the right or different tools to split that saw in a heart beat on my dime but not his because if things go bad all that will come of it is a bad relationship between us.

 

[BuckthornBonnie]

I’d give him a fair offer on it, split the case, and get a good used case or see if the bearing area can be fixed (tricky).

That way he’s happy and you have a fun beast of a project with no rush to finish.

 

[Ax-man]

I have given it a little thought to buy the saw from him but he wants to keep the saw in the hopes it can be fixed without spending a lot of money on it. Good luck with that one. Last time we talked which was last Monday he said he had "another guy'' who might have a crankcase who could take parts off his saw to put onto this other saw. I decided to let him do what he wanted to do because if this other guy screws it up it won't be my fault. This has been a losing deal for me as it is , the only thing I am getting out of this is it has added to my saw repair knowledge .

 

[Ketchup]

Maybe a bad bearing? 88s fry easier than you would think. I've seen two of them now with overheated cranks. Splitting one isn't hard, but the parts are spendy.
They're always expensive to work on. He probably won't get far with the other guy either.

 

[super3]

The seal seats in the outer bearing race, not the case half.

 

[Ax-man]

Interesting , I have suspected that the bearing was bad but can't feel any movement of the crank to really tell if it is bad. This saw has had a hard life and you tell it has gotten really hot in this area around the seal and bearing. The tech at the dealer remembered working on this saw for a bad clutch that had gotten really hot . An over heated crank would be a good suspect .

I took the saw out to dealer to see if I had that seal was in where it should be and they said I put it in right . This bearing race has me curious is that something that can be removed without splitting the case ?? I am not an engine rebuilder per say but have split a half a dozen saws over the years and the area around the bearing and seal have always been part of the crankcase half

 

[rupedoggy]

Ax-man you are getting good advise. Don't doubt it or question it just because YOU haven't seen it. That'a arrogant.

 

[Ax-man]

I know I am getting good advice and I am not doubting this advice one bit. I am just a little out of comfort zone on this one and thankful for the input. If I seem like I am coming off as arrogant that is not my intention. There is a reason why this saw ended up the way it did and it would be nice to know why and how it happened in case I run into some thing like this in the future and how to look for it.

 

[super3]

This bearing race has me curious is that something that can be removed without splitting the case ??

No, it's part of the bearing.

 

[Ax-man]

OK, I'm with you now. I guess I wasn't wording myself correctly. Sorry about that.

 

[Ketchup]

I'm no expert, but I have gotten burned on these saws before.

You are right that you have to split the case and press out the bearings to replace them. You should do both bearings if you do one. If you suspect the case half that should go too. The cranks are frequently scorched as well.

It's a complete rebuild of the saw. There are very few AM parts for these saws, so parts cost a lot. I doubt a tech would do it for less than $500 with parts, probably more like $800. I would say it's a lost cause unless the guy wants to spend real money or sell it as a project.

But it's an easy build if you take your time. Everything is big and obvious.