Hi,
So I have heard multiple times on the forum that the big end bearings can’t be changed. To buy a new crankshaft.
I didn’t like the idea that you have to spend hundreds of dollars just to replace a bearing if it fails. So I did some digging and looked in to how I could do so from home.
I got a cheap crank to test it out
Firstly I pressed out the pin from between the webs
Then aligned it back up and pressed it all back together as if I had put a new bearing in.
Then came the truing…
I needed a way to support the crank without needing to spend hundreds of dollars on some specialist jig.
I came across a 3d printable trying stand and had asked a friend if he could print it.
He charged $20 AUD the bearings were $7 AUD and hardware $10 AUD (note the choice of stihl colours!)
I then went through the process of truing it. I managed to get one side to less than 0.005mm runout on the dial indicator as in the video below. However the other side was more. Then when I went to tweak the other side the first side went out.
Video of less than 0.005mm runout.
View attachment IMG_4408.MOV
The closest I could get was about 0.03mm runout. That’s certainly within acceptable tolerances..
so with a small investment in a dial indicator (a cheapie will be fine) a stand and some way of holding the crank, it’s certainly possible and far cheaper than hundreds on another crankshaft, just to replace the bearing!
So I have heard multiple times on the forum that the big end bearings can’t be changed. To buy a new crankshaft.
I didn’t like the idea that you have to spend hundreds of dollars just to replace a bearing if it fails. So I did some digging and looked in to how I could do so from home.
I got a cheap crank to test it out
Firstly I pressed out the pin from between the webs
Then aligned it back up and pressed it all back together as if I had put a new bearing in.
Then came the truing…
I needed a way to support the crank without needing to spend hundreds of dollars on some specialist jig.
I came across a 3d printable trying stand and had asked a friend if he could print it.
He charged $20 AUD the bearings were $7 AUD and hardware $10 AUD (note the choice of stihl colours!)
I then went through the process of truing it. I managed to get one side to less than 0.005mm runout on the dial indicator as in the video below. However the other side was more. Then when I went to tweak the other side the first side went out.
Video of less than 0.005mm runout.
View attachment IMG_4408.MOV
The closest I could get was about 0.03mm runout. That’s certainly within acceptable tolerances..
so with a small investment in a dial indicator (a cheapie will be fine) a stand and some way of holding the crank, it’s certainly possible and far cheaper than hundreds on another crankshaft, just to replace the bearing!