You have to split the cases now to fix that bearing with any luck but the case is prob wiped out from it spinning in there.I think some person used to over tighten the chain a lot. Well rip it down and see.
Pressure testing a Dolmar 5100s - what am I doing wrong
- Thread starter sevensandeights
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The outer race of the bearing is what you have your pointer on. That should be an airtight press fit into the case. The inner race of the bearing is the ring on the crankshaft & should also be an airtight press fit to that. The seal is the black/brown rubbery bit between them which in this case is integrated into the bearing (often the seal will be a separate item that is pressed in place outside the bearing).
If the outer race is spinning within the crank case pocket you have a significant problem.
I wouldn't be surprised if the threaded holes for the machine screws there go all the way into the case either.
If the outer race is spinning within the crank case pocket you have a significant problem.
I wouldn't be surprised if the threaded holes for the machine screws there go all the way into the case either.
sevensandeights
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Yuck - not what I wanted to hear but unfortunately what I expected.
Just out of curiosity. What is the process for replacing the bearing? Are the bearings pressed onto the crankshaft and then the case is pressed back together?
Just out of curiosity. What is the process for replacing the bearing? Are the bearings pressed onto the crankshaft and then the case is pressed back together?
Spun bearings are a pain! Ideally you’d replace the case half or if not too bad install a bearing with 609 loctite, but I wonder if, after cleaning the gap between the pocket and the bearing with brake cleaner externally (without any disassembly of the cases) while rotating the spin bearing and then dry with compressed air followed by retaining or wicking loctite will work? @pioneerguy600 told me about his use of different loctites, I don’t know if he can chime in here. Could wicking Loctite 290 be used here while everything is still assembled Jerry? If there is enough space maybe even a retaining compound like 609?
Just depends how far the OP wants to go. This is the least invasive so long as the bearing feels smooth though as no disassembly is required at all.
Just depends how far the OP wants to go. This is the least invasive so long as the bearing feels smooth though as no disassembly is required at all.
I've also had success getting loctite to whick into gaps to fix air leaks. I doubt it as a solution in this instance though as there's more than likely an issue with the bearing that has led to it spinning.... & if the case wouldn't hold it I doubt retaining compound by itself will.
I would think it needs to come apart &, if the clearance isn't too great either knurl or punch the surfaces to give them raised areas & then re-assemble in the usual manner (with a healthy smear of retaining compound).
If clearance is too much for that to work you may be able to shim it or Mill the pocket out for an oversized bearing if one (with the appropriate seal) is available
I would think it needs to come apart &, if the clearance isn't too great either knurl or punch the surfaces to give them raised areas & then re-assemble in the usual manner (with a healthy smear of retaining compound).
If clearance is too much for that to work you may be able to shim it or Mill the pocket out for an oversized bearing if one (with the appropriate seal) is available
sevensandeights
ArboristSite Operative
Thanks for all the comments and support thus far - very much appreciated. This project is becoming bigger and possibly more expensive than what the saw is worth. I have learned a lot though. Really love this saw but the lack of a local dealer and the fact that Dolmar/Makita is out of the gasoline saw business makes me not want to dump much more time/money into it.
Plan is to look for a used case with good bearings and go from there. Anything involving splitting a case and reassembling is a bit out of my league. I don't have a press or a way to heat up the case to help receive the new bearings.
Trying to wick loctite in would be a cheap and easy fix. My concern though is that the case casting has that lip on it which covers 60% of the area where the loctite would need to go.
Plan is to look for a used case with good bearings and go from there. Anything involving splitting a case and reassembling is a bit out of my league. I don't have a press or a way to heat up the case to help receive the new bearings.
Trying to wick loctite in would be a cheap and easy fix. My concern though is that the case casting has that lip on it which covers 60% of the area where the loctite would need to go.
sevensandeights
ArboristSite Operative
Done - thanks for the suggestion LW
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For what it is worth- if you have a complete chainsaw to start with- you have a piston stop hiding in the recoil starter cover.
sevensandeights
ArboristSite Operative
Good thinking Bob - definitely would have been easier to use the pull string from the saw since it was sitting right next to me on the work bench - didn't that of that at the time! Instead I spent 30 minutes looking for an old pull string I replaced in a Polaris ATV a few months ago. Couldn't find it so I ordered the tool.
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If it is the metal "tool" you have ordered- I suggest sticking to rope.
sevensandeights
ArboristSite Operative
I did get the metal tool - it left a small indentation in the top of the piston.
sevensandeights
ArboristSite Operative
So the saga continues. I found a complete case but the seller can't guarantee that it will pass a leak test. He claims the bearings are good but can't guarantee the seals. Not unreasonable for selling a used case I suppose. However, the clutch side seal is unobtanium. Can't find it anywhere and have been told that the only way to get the seal is to buy the bearing with the seal already installed. Likely wouldn't be able to remove it without destroying it.
It looks like Jacks small engines says that a new clutch side bearing/seal combo is $20. I'd buy the cases, p/v test them with your jug, if they fail buy a new bearing/seal and install it. If the new cases pass, smile and move on with the work.
sevensandeights
ArboristSite Operative
Done deal. Bought the case and some supplies to swap the piston and cylinder. Hopefully the seals are good - otherwise I'm going to need some more help from the forum!
sevensandeights
ArboristSite Operative
I've been out of town for the past week but am heading home today. New to me case should be there already. Plan to put my cylinder on it and pressure test. Assuming things check out I will then have to swap the rest of my saw parts over. Is there anything I need to watch out for when swapping the ignition parts?
sevensandeights
ArboristSite Operative
It's back together and working! Haven't cut any wood yet but she sounds good and the idle adjustment screw actually works now since the air leak is gone. As usual I learned some things during the process:
1.) The $12 tool kit with the red plastic piston ring compressors is money well spent. Yes you can use your fingers or a zip tie but the kit makes it so much easier. You also get the block that supports the piston and some plastic piston stops.
2.) Chainsaws make a horrible noise if you forget to put the wristpin needle bearing back in before connecting the piston. Had everything back together and was excited to see if it would run and but it sounded weird when I pulled the starter rope. Sounded really bad when it started! Took me a bit to figure out what the problem was. Initially thought it was the muffler vibrating against the new to me case.
3.) For this saw, the fuel line has to be oriented in a specific way when it comes out of the tank. There is a "tab" that has to face a certain way so the hose doesn't kink when it comes up through the carb housing. Not sure why I ever removed the fuel line in the first place because it was unnecessary but it was fun disassembling everything again to get it at and fix the problem. The repair manual helped me solve this issue.
Thanks to all for their advice.
1.) The $12 tool kit with the red plastic piston ring compressors is money well spent. Yes you can use your fingers or a zip tie but the kit makes it so much easier. You also get the block that supports the piston and some plastic piston stops.
2.) Chainsaws make a horrible noise if you forget to put the wristpin needle bearing back in before connecting the piston. Had everything back together and was excited to see if it would run and but it sounded weird when I pulled the starter rope. Sounded really bad when it started! Took me a bit to figure out what the problem was. Initially thought it was the muffler vibrating against the new to me case.
3.) For this saw, the fuel line has to be oriented in a specific way when it comes out of the tank. There is a "tab" that has to face a certain way so the hose doesn't kink when it comes up through the carb housing. Not sure why I ever removed the fuel line in the first place because it was unnecessary but it was fun disassembling everything again to get it at and fix the problem. The repair manual helped me solve this issue.
Thanks to all for their advice.
Thanks for the update, & shared learning points... I'm sure many here would have neglected to mention your "2.)"
Happy cutting
Happy cutting
