Alphadelta
ArboristSite Member
So during COVID found a guy in a farm town selling a MS440 for $200, it was run hard and put away wet, but it ran, so I bought it. Then I got the great idea to "fix" what wasn't broken. Here is my advice to anyone who runs into any similar issues that I had along with a MASSIVE thank you to the list of people who got my saw back up and running.
Taking it apart I realized the entire saw needed to be stripped down and cleaned, after this was completed and I was attempting to put the bolt on the flywheel I sheared the bolt off with a impact gun. I attempted to use a drill press and drill out the old threads to install a nut or stud. This DID NOT work in the slightest. The sudden shearing motion of the impact gun work hardened the remaining metal threads. The only option to drill through this was carbide. First piece of advice.
You can buy decent quality carbide bits from Home Depot for $25 and for the money, are very nice. These worked but quickly my lack of a sturdy way to clamp the entire saw down led to the bit walking and it becoming irreparable in my own shop. So onto plan B.
Takeaways:
- If this happens to you, the most optimal way to go about this is to remove the crank get it ROCK SOLID in your drill press and drill it out and tap it for a stud or a bolt.
- Ideally if you're dead set on not buying an OEM used or new, or aftermarket, contact a machine shop. Just keep in mind while with the right tools and knowledge this is an easy fix for them, but you're going to pay for their expertise. May not hurt to get a quote from a shop or two.
- Considering the prior two options are not available or you don't want too, buy a used OEM crank. You may have to scrounge until one comes up, but just comparing a used OEM to a brand new aftermarket was noticeable to even my untrained eye.
After this I consulted many of you on the forums, bent anyone's ear I could and after buying an whole list of HL parts was able to pick up a used OEM crank from @kenton.a.frank along with some plastic covers. Thus began learning how to completely tear down a $500-$900 saw and NOT destroy it. There are lots of videos online of how to do this without the "proper" tools, which essentially comes down to patience and a heat gun. Thermal expansion of metal is in the ballpark of .001 thousands per 100 degrees Fahrenheit. These are tight tolerances between the bearings and the crank case so you don't need too much heat to get the case to expand where a light tap on a hammer will allow the case to split. If you want to know more about thermal expansion look here. If you want to really get into it, I hope you like math. Reassembly is much of the same, patience and heat. I believe the correct way is bearings into the crank case followed by the crank shaft. However I found it easiest to freeze the crankshaft overnight and then slide the bearings on; then place the entire assembly into the saw. Do some research, find what works best for you and make sure you center the crank after you're done.
Takeaways:
- GO SLOW, you can easily mar, scratch, dent, etc mating surfaces when doing this. Try to use as little force as possible and tools less prone to damaging the metal. I used a brass hammer and light pressure with a screwdriver. I have heard of some dudes using brass screw drivers, it's a "smoke them if you got them" situation.
- If you are nervous about using a heat gun and all of that. Invest in the tools to "properly" split the saw, aftermarket options are widely available from sites such as HLsupply. Here is one made for Stihl https://www.hlsproparts.com/product-p/pj91040.htm. While the upfront cost is higher you can hang onto these in the event you ever need them again.
- Consult the service manual, while you won't be using the same tools or techniques you can get an idea of how it's meant to be torn down, tested, put back together and serviced. Here is the link for my saw just so you get an idea. https://www.manualslib.com/manual/1302030/Stihl-Ms-440.html
- Lastly DOUBLE and TRIPPLE check everything, I had to re-split my saw twice because I messed up the bearing orientation.
- BUY OEM BEARINGS! I talked to the engineering department at NSK who stated it is easiest to just buy the bearings straight from the dealer. Do I think that aftermarket bearings are good, sure, they obviously the same specs, but I doubt tolerances are as tight. Lastly I want these things to last, I don't want to ever split this case again if I can help it. I trust OEM to last the longest, of course, in my opinion. Also the guy at NSK also told me the same thing in a more eloquent way.
Once the crank was reassembled, I realized God hates me and my tank had fallen off the bench and cracked. After a lot of waiting finally @northwestsaws found me a tank. From there it was just reassembly, I bought all new hoses, seals and filters, here I just brought aftermarket off Amazon. Unlike precision items such as a crank shaft or bearings that need to run at high RPM with high load, hoses are pretty mundane and I am not a pro so my livelihood does not depend on my saws uptime.
Finally running! After reading a bunch, and I do mean A BUNCH, the best practice seems this - after a rebuild you should add some extra oil to the tank and only max out the RPM's while cutting. This means no goosing it, start it up, let it idle, then begin your cut. I let mine just idle for about 5 minutes on it's first start just to get everything oiled and ready to go. Then I started cutting. But opinions on this seem to vary so do your research and do what you think is best. If all else fails just follow the service manuals.
Well all this ends the saga of the MS440 snagged for a good deal (knock on wood) then promptly broken. Only took me 20 months from time of purchase to break it, and then rebuild it, I'll take it. I wanted to say I learned a lot from everyone here, and this experience and advice of others has greatly advanced my knowledge. I went through my old posts and tried to find everyone that helped. So I owe @oddsaws @BuckthornBonnie @Mad Professor @brad ruch @alexcagle @huskihl @pioneerguy600 @Motherboard @rupedoggy @lone wolf @Stihlman @holeycow @Snatch Block and @PV Hiker, all a beer you guys rock.
Thanks again. Pictures bellow. Best of luck to anyone in a similar situation.
Taking it apart I realized the entire saw needed to be stripped down and cleaned, after this was completed and I was attempting to put the bolt on the flywheel I sheared the bolt off with a impact gun. I attempted to use a drill press and drill out the old threads to install a nut or stud. This DID NOT work in the slightest. The sudden shearing motion of the impact gun work hardened the remaining metal threads. The only option to drill through this was carbide. First piece of advice.
You can buy decent quality carbide bits from Home Depot for $25 and for the money, are very nice. These worked but quickly my lack of a sturdy way to clamp the entire saw down led to the bit walking and it becoming irreparable in my own shop. So onto plan B.
Takeaways:
- If this happens to you, the most optimal way to go about this is to remove the crank get it ROCK SOLID in your drill press and drill it out and tap it for a stud or a bolt.
- Ideally if you're dead set on not buying an OEM used or new, or aftermarket, contact a machine shop. Just keep in mind while with the right tools and knowledge this is an easy fix for them, but you're going to pay for their expertise. May not hurt to get a quote from a shop or two.
- Considering the prior two options are not available or you don't want too, buy a used OEM crank. You may have to scrounge until one comes up, but just comparing a used OEM to a brand new aftermarket was noticeable to even my untrained eye.
After this I consulted many of you on the forums, bent anyone's ear I could and after buying an whole list of HL parts was able to pick up a used OEM crank from @kenton.a.frank along with some plastic covers. Thus began learning how to completely tear down a $500-$900 saw and NOT destroy it. There are lots of videos online of how to do this without the "proper" tools, which essentially comes down to patience and a heat gun. Thermal expansion of metal is in the ballpark of .001 thousands per 100 degrees Fahrenheit. These are tight tolerances between the bearings and the crank case so you don't need too much heat to get the case to expand where a light tap on a hammer will allow the case to split. If you want to know more about thermal expansion look here. If you want to really get into it, I hope you like math. Reassembly is much of the same, patience and heat. I believe the correct way is bearings into the crank case followed by the crank shaft. However I found it easiest to freeze the crankshaft overnight and then slide the bearings on; then place the entire assembly into the saw. Do some research, find what works best for you and make sure you center the crank after you're done.
Takeaways:
- GO SLOW, you can easily mar, scratch, dent, etc mating surfaces when doing this. Try to use as little force as possible and tools less prone to damaging the metal. I used a brass hammer and light pressure with a screwdriver. I have heard of some dudes using brass screw drivers, it's a "smoke them if you got them" situation.
- If you are nervous about using a heat gun and all of that. Invest in the tools to "properly" split the saw, aftermarket options are widely available from sites such as HLsupply. Here is one made for Stihl https://www.hlsproparts.com/product-p/pj91040.htm. While the upfront cost is higher you can hang onto these in the event you ever need them again.
- Consult the service manual, while you won't be using the same tools or techniques you can get an idea of how it's meant to be torn down, tested, put back together and serviced. Here is the link for my saw just so you get an idea. https://www.manualslib.com/manual/1302030/Stihl-Ms-440.html
- Lastly DOUBLE and TRIPPLE check everything, I had to re-split my saw twice because I messed up the bearing orientation.
- BUY OEM BEARINGS! I talked to the engineering department at NSK who stated it is easiest to just buy the bearings straight from the dealer. Do I think that aftermarket bearings are good, sure, they obviously the same specs, but I doubt tolerances are as tight. Lastly I want these things to last, I don't want to ever split this case again if I can help it. I trust OEM to last the longest, of course, in my opinion. Also the guy at NSK also told me the same thing in a more eloquent way.
Once the crank was reassembled, I realized God hates me and my tank had fallen off the bench and cracked. After a lot of waiting finally @northwestsaws found me a tank. From there it was just reassembly, I bought all new hoses, seals and filters, here I just brought aftermarket off Amazon. Unlike precision items such as a crank shaft or bearings that need to run at high RPM with high load, hoses are pretty mundane and I am not a pro so my livelihood does not depend on my saws uptime.
Finally running! After reading a bunch, and I do mean A BUNCH, the best practice seems this - after a rebuild you should add some extra oil to the tank and only max out the RPM's while cutting. This means no goosing it, start it up, let it idle, then begin your cut. I let mine just idle for about 5 minutes on it's first start just to get everything oiled and ready to go. Then I started cutting. But opinions on this seem to vary so do your research and do what you think is best. If all else fails just follow the service manuals.
Well all this ends the saga of the MS440 snagged for a good deal (knock on wood) then promptly broken. Only took me 20 months from time of purchase to break it, and then rebuild it, I'll take it. I wanted to say I learned a lot from everyone here, and this experience and advice of others has greatly advanced my knowledge. I went through my old posts and tried to find everyone that helped. So I owe @oddsaws @BuckthornBonnie @Mad Professor @brad ruch @alexcagle @huskihl @pioneerguy600 @Motherboard @rupedoggy @lone wolf @Stihlman @holeycow @Snatch Block and @PV Hiker, all a beer you guys rock.
Thanks again. Pictures bellow. Best of luck to anyone in a similar situation.
glad it’s finished and I’m sure you’ve learnt a lot. Crankshafts are hardened anyway so you won’t drill one too easily regardless of work hardening or not.
