crankshaft stiff with new bearings?

[thompson1600]

I took an 026 apart and put in new bearings. The bearings were Stihl and open on one side, the other side had a small plastic partial shield (open side was put facing in toward the crankshaft). I put the new bearings in and then the crankshaft. Everything went fine. Was able to center the crankshaft and relieve axial pressure and the shaft spun freely. Then I put the oil seals on (using Stihl oil seal tools). I used a rubber mallet for that. Now the crankshaft doesn't spin freely and is stiff. It is not rubbing against the sides, and the bearings don't appear to have moved back out into the crankshaft housing. From the top it doesn't appear anything is rubbing and I don't hear anything rubbing when I turn the crankshaft. It is quite stiff though.

Using the Stihl install tools, could I have pushed the seals too far in, I don't think so. I'm just a little stumped about why it spins freely with the new bearings in and then gets real stiff when I put the oil seals in. Even lightly using the rubber mallet after putting the seals on doesn't help to relieve axial pressure.

Any suggestions or ideas?

Thanks

Tom

 

[Lewis Brander]

Seals:

Hi Tom. Not sure what to say here about the seal installation, except to ask if you lubed the seals before installation or put them in dry. I always use a bit of white lube or some sort of grease to lube the seals before I install them. Even doing this there will be some slight drag when the crank is rotated, but sounds like you have excessive drag. I'd try and work a bit of lube into the seal area. JMO. Lewis.

 

[thompson1600]

I used oil, not a grease. Does a grease work better, and if so, what brands have worked for ya? Thanks

Tom

 

[tree monkey]

i don't think you have anything to worry about. run it and see if it changes.

 

[Lewis Brander]

Greases:

I've use different lubes to lubricate seals, such as white lube, vaseline to a good grapite chassie lube. If the seals have been lubed with oil they should be all right. As was said, assemble the saw and run her and check to see if she has loosened up. As I said, there is usually some drag, even in lubed new seals. Good luck. Lewis.

 

[jimbo1490]

Many small engines go together using guide pins. These have a 'push fit' into their corresponding socket on the other case. The c'shaft bearings themselves also have a push fit into their races. These push fit parts can create stress (slight bending) when the cases are assembled. I have put together several small engines where this happens, and the crank turn too stiff once all the screws are tightened. It usually happens when you draw the case halves together with the case screws. Try carefully tapping the case with a hammer. Don't beat on it! You're just trying to get everything fully seated and aligned by setting up some percussive vibrations. This has worked for me most recently on an older Stihl for which I swapped out a cracked case. Other than this, you are probably looking at a mis-assembled crank bearing or seal which lacks proper running clearance.

Jimbo

 

[Saw Man]

If the case screws were tightened in the correct order, and to the correct torque that can still happen in most any quality saw.

Here's a tip that must be done carefully, and will both 'loosen up' the crank, and 'true run' it.

Flywheel, clutch, piston, and oiler off.
Rotate crank to get a 'feel' of force needed.
Crankcase setting down on bottom, secure with one hand.
Fit a nut over each threaded end so the nut is just past flush with the threads.
Using a small BRASS or better yet a LEAD hammer lightly & squarely...lightly & squarely give a clean sharp tap to one side then the other.
Rotate crank to compare 'force'. Most often is easier.
Observe the distances between the upper crank pin & the crankcase sides. Often the crank is off set to one side more than the other. Using a feeler guage determine the TOTAL distance between the sides, divide it in half, and again tap the crank end on the narrower side to even out the distance. That moves the crank towards the wider side.
This will center the crank in relationship to the bore, providing a more 'true run', and also will usually free up the crank more.
As stated by others make sure the seals, and bearings were lubed, if not use some engine oil at this point. Some resistance must be felt to ensure a good seal fit.

 

[stihltech]

seals

When I put a saw together, The most important thing is that the crank spins freely in the bearings without the seals. After the seals are installed, the force to turn the crank will increase, but as long as it will turn with your fingers, it will be OK. If it is tighter than that, I would remove the seals and make sure they are not in the bore too far.