Stihl 034 rebuild - Advise on methods to install crankshaft/bearings..

[rtpgmr]

Hello.. I am rebuilding a stihl 034. This is my first saw rebuild where I have to split the cases. It has a bad cylinder/piston. I did not know the history of the saw, so I split the case and will be replacing the crank bearings and seals. I am hoping to get some advise on the best method of installing the bearings and crankshaft. From the research that I have done I have seen the following recommended:

1) install the bearings in the case on both sides before installing the crankshaft and close the cases together.
2) install the bearings on the crankshaft first and then fit the crankshaft between the case halves and close.

Both methods refer to heat and freezing components to be successful....

Thanks in advance for any hints or suggestions..

Rtpgmr

 

[nmurph]

The manual states to heat the case to 250° and install the bearings in the case. Then install the crank.

 

[CWME]

I have done both. I found that putting the bearings in the cases first was much simpler for me. I will be doing it that way from here on out. I have a whole thread on rebuilding a couple of 036 saws last winter if you search for it.

I just did a 028 last week and used the same methods described there except bearings first. Simple and it works.

Edit to add that I did the 036 with the bearings on the crank and wouldn't suggest that route. As stated above, much better to put in case first.

 

[rtpgmr]

I have done both. I found that putting the bearings in the cases first was much simpler for me. I will be doing it that way from here on out. I have a whole thread on rebuilding a couple of 036 saws last winter if you search for it.

I just did a 028 last week and used the same methods described there except bearings first. Simple and it works.

Edit to add that I did the 036 with the bearings on the crank and wouldn't suggest that route. As stated above, much better to put in case first.

Thanks for the quick response. I will search for the threads and read.. I am interested in how you were able to get the crankshaft in both bearings and close the cases with such a tight fit.

 

[rtpgmr]

The manual states to heat the case to 250° and install the bearings in the case. Then install the crank.

Thanks for the response.. Looks like I need to follow that advise.. I need to know how the get the crankshaft inserted into the the crank bearings and get the cases put together with such a tight fit.. I will continue to search ...

 

[blsnelling]

Install the flywheel side bearing onto the crank. Heat the case and drop the crank/bearing in. Do it right and it will literally fall right in. There's no need to freeze the bearing. Install the PTO side bearing into the other case half, same method, using heat. Then start the PTO side case/bearing onto the crank. You may have to carefully tap it in order to catch a couple threads on the case bolts. Then CAREFULLY & EVENLY pull the case halves together. When done, you'll have to hit the ends of the crank with a brass hammer, or similiar, in order to release the stree on the inner races. This is referred to as centering the crank.

 

[rtpgmr]

Install the flywheel side bearing onto the crank. Heat the case and drop the crank/bearing in. Do it right and it will literally fall right in. There's no need to freeze the bearing. Install the PTO side bearing into the other case half, same method, using heat. Then start the PTO side case/bearing onto the crank. You may have to carefully tap it in order to catch a couple threads on the case bolts. Then CAREFULLY & EVENLY pull the case halves together. When done, you'll have to hit the ends of the crank with a brass hammer, or similiar, in order to release the stree on the inner races. This is referred to as centering the crank.

Thanks for the information. I will follow your advise. Rtpgmr

 

[Bizzaro]

Bring an old thread back to life............has anyone ever "had to" replace crank bearings on the 034, or are you doing it because you have the cases split? I am a minimalist at heart. And I truly believe q c and overall quality has diminished with time. While I realize that it may be wise to replace the bearings if their is a failure rate that would dictate they be replaced as a precaution and preventative maintenance. On the other hand, if the bearings are good and don't ever fail, why replace them. In my opinion, older parts are built better. Just my opinion. Almost everything is sourced in China these days. While I do not know if the bearings follow this model, if 034's do not have a bearing failure rate that dictates replacement, I am leaning towards not messing with them. Now on the other hand, if these " original" bearings do fail of course it makes sense to replace them while you are in there? Opinions and facts please. And has anyone ever heard of the bearings failing on the 034??

 

[BuckthornBonnie]

Yes... many times. The failures are usually obvious and aren’t some sort of issue with the series, though. Typically they’re high hour saws with other problems as well.

 

[Tobystihl]

Bring an old thread back to life............has anyone ever "had to" replace crank bearings on the 034, or are you doing it because you have the cases split? I am a minimalist at heart. And I truly believe q c and overall quality has diminished with time. While I realize that it may be wise to replace the bearings if their is a failure rate that would dictate they be replaced as a precaution and preventative maintenance. On the other hand, if the bearings are good and don't ever fail, why replace them. In my opinion, older parts are built better. Just my opinion. Almost everything is sourced in China these days. While I do not know if the bearings follow this model, if 034's do not have a bearing failure rate that dictates replacement, I am leaning towards not messing with them. Now on the other hand, if these " original" bearings do fail of course it makes sense to replace them while you are in there? Opinions and facts please. And has anyone ever heard of the bearings failing on the 034??

Hi, on my last one, (heavily used by me professionally) the mains started to rumble, never had them fail completely though!

 

[rupedoggy]

I tend to agree with that. If it ain't broke don't fix it. HOWEVER if I see plastic cages and it is going to be a premo build, I will look to replace those because they get brittle and the gasoline we have now also makes them fail. If I reuse bearings they get a close inspection with magnifiers. No rust, rough spots, or clunkynesss allowed.

 

[mike-s]

The problem with keeping bearings is that in order to split the case, the bearing surfaces (balls and races) take all the stress of pulling the crank out of the bearings. It's unavoidable unless it's a clamshell design. Similar with the common method of simply catching a few threads and tightening when closing the case. The proper way is to replace bearings any time the case is split. Heat the halves slowly in an oven to ~300 degrees F, throw the bearings in the freezer for an hour while doing that and install the new bearings into the case halves - if they don't fall in, it only takes a very light tap (on the outer races).

When closing the case, the best method is to pull the crank into the bearing. Both sides of the crank are threaded, you just need to rig a sleeve which pulls the crank into the bearing, pushing against the inner race. That way there's no stress on the bearing surfaces (bonus points if you alternate with gently tapping in the alignment pins, but they take way less force than crank into bearing. That can be as simple as a cut-down piece of pipe (or perhaps a 3/4" drive socket, if dimensions allow), some appropriately sized washers, and the existing flywheel nut/clutch/whatever. The concept is to avoid any significant force on the bearing balls/race surfaces. Specifics depend on the particular engine.

Or, reuse bearings and pound everything together with a brass hammer. Your choice.

 

[Vintage Engine Repairs]

Grab a set of tools from @Mattyo to pull crank, use head and chill method to instal bearings. I use a heat gun on the bearing pocket and take it to 200c, freeze the bearing for an hour plus and they slip in.

 

[Mattyo]

The problem with keeping bearings is that in order to split the case, the bearing surfaces (balls and races) take all the stress of pulling the crank out of the bearings. It's unavoidable unless it's a clamshell design. Similar with the common method of simply catching a few threads and tightening when closing the case. The proper way is to replace bearings any time the case is split. Heat the halves slowly in an oven to ~300 degrees F, throw the bearings in the freezer for an hour while doing that and install the new bearings into the case halves - if they don't fall in, it only takes a very light tap (on the outer races).

When closing the case, the best method is to pull the crank into the bearing. Both sides of the crank are threaded, you just need to rig a sleeve which pulls the crank into the bearing, pushing against the inner race. That way there's no stress on the bearing surfaces (bonus points if you alternate with gently tapping in the alignment pins, but they take way less force than crank into bearing. That can be as simple as a cut-down piece of pipe (or perhaps a 3/4" drive socket, if dimensions allow), some appropriately sized washers, and the existing flywheel nut/clutch/whatever. The concept is to avoid any significant force on the bearing balls/race surfaces. Specifics depend on the particular engine.

Or, reuse bearings and pound everything together with a brass hammer. Your choice.

its not unavoidable, my tools do it on a regular basis....only pressure is on the inner race ...and the crank gets pulled through sold hundreds of tool kits worldwide

 

[Vintage Engine Repairs]

its not unavoidable, my tools do it on a regular basis....only pressure is on the inner race ...and the crank gets pulled through sold hundreds of tool kits worldwide

I think he means, when splitting the case.

 

[mike-s]

its not unavoidable, my tools do it on a regular basis....only pressure is on the inner race ...and the crank gets pulled through sold hundreds of tool kits worldwide

OK. Did a quick search. I only found an assembly tool which does it right. Where's the disassembly tool which gets behind the inner race on an assembled engine to separate it from the crank?

I think he means, when splitting the case.

It's not just what I meant, it's what I said.

 

[jltrent]

I have done a bunch and they seem to work right apparently. I heat the case up press in the bearings on each side and press the crank in the flywheel side and then use long bolts to pull it all together. Sometimes a slight tap on the end of the crank with a piece of wood against will set the crank.

 

[BuckthornBonnie]

OK. Did a quick search. I only found an assembly tool which does it right. Where's the disassembly tool which gets behind the inner race on an assembled engine to separate it from the crank?
It's not just what I meant, it's what I said.

Easy... Spoon guy was supporting your statement.

 

[Vintage Engine Repairs]

OK. Did a quick search. I only found an assembly tool which does it right. Where's the disassembly tool which gets behind the inner race on an assembled engine to separate it from the crank?
It's not just what I meant, it's what I said.

Relax Mike, I was agreeing with you.

 

[Mattyo]

OK. Did a quick search. I only found an assembly tool which does it right. Where's the disassembly tool which gets behind the inner race on an assembled engine to separate it from the crank?
It's not just what I meant, it's what I said.

Sorry...did I read something wrong? It's not possible to grab the inner race for dissassembly because they are ...mostly...pressed tight up against the crank lobe leaving no room to grab them. Unfortunately this does put considerable lateral force on the bearings and I would contend that they require replacement after this is done. My assembly tools do only put pressure on the inner race.