To rebuild or just run it

[NCPT]

All my parts came in and I got started on this today. Everything is apart and cleaned. Went to install new piston in the cylinder and couldn't get it to slide in. It finally dawned on me the piston is 42.5mm and the cylinder for the 025 is 42mm....so I just ordered a 42mm piston. Not sure what I was thinking when I ordered the 42.5mm piston but man I was ready to get this put back together lol.

This is my first rebuild on a chainsaw and it's been interesting for me so far. Are pro saws easier to work on than this 025 clamshell saw? I'm assuming they are. Thanks

 

[HarleyT]

Damn! Did you get the plate number of that truck???

 

[NCPT]

I tried this stuff for the first time today. It was advertised as spray and wipe bit I used compressed air instead of wiping. Worked pretty good and I figured I would try it since I don't have running water in my shop yet.

 

[NCPT]

Damn! Did you get the plate number of that truck???

Lol, you think I got a mess?

 

[Okie]

What kind of sealer you going to use on the clamshell?

Look at your bearings really close and if they have the plastic bearing separators replace them with ones that are all steel before they start crumbling. The bearings remove and install easily if they are warm. (about 170 degrees)

You might look through this where I was into a MS250 (clamshell) awhile back.
My first time into a clamshell ms250. Got lots of good info from the experts here about which parts I needed to replace with better parts, etc.

I used Yamahabond sealer (from flea bay) and put spacers on the clamshell bolts (so they could be drawn down snug on the bottom half) and let the bond dry for 12 hrs so all would stay bonded together when re-installing into the case.
I also did away with the plastic type bearings and pressure tested the block after I got it bolted in the case and before installing all external parts to the block. (too make sure the block did not have any leaks)

https://www.arboristsite.com/community/threads/ms250-need-expert-advice.319343/#post-6533571

 

[NCPT]

What kind of sealer you going to use on the clamshell?

 

[Mad Dog]

Re-build it. It's the simplest thing in the world to do.

 

[HarleyT]

View attachment 651425

I can tell by your hand that you are an accountant.....

 

[NCPT]

I can tell by your hand that you are an accountant.....

Lol, my accountant's hand feels funny when I shake it.

 

[NCPT]

I accidentally blew out this yellow stuff out of the back of the flywheel. What is it and what do I use to replace it?

 

[NCPT]

I was able to sand most of the scoring out of the cylinder with 600 grit and a scotch brite pad. Scraped old sealant and lightly sanded the base. Is it clean enough or do I need to take more off? I'm not looking to get this thing perfect, I just want to get a good running saw that I could let someone borrow if needed.

 

[HarleyT]

I used to blow a lot of that stuff out when I was a teen....

 

[HarleyT]

Lol, my accountant's hand feels funny when I shake it.

Well, try your left hand....

 

[NCPT]

I used to blow a lot of that stuff out when I was a teen....

Hard to break old habits...

 

[NCPT]

Well, try your left hand....

Again....hard to break old habits lol

 

[m21bmr]

This is my first rebuild on a chainsaw and it's been interesting for me so far. Are pro saws easier to work on than this 025 clamshell saw? I'm assuming they are. Thanks

I haven't rebuilt an especially high number of saws, but I have probably had 10 or more clamshell style engines apart for repairs, and 3 or 4 magnesium case bolt-on cylinder style saws. To me, it really depends how deep you are going into the saw. Just top end work is somewhat easier on the "pro" construction style with a bolt on cylinder, as you have to take apart less of the engine to work on it. If you are dealing with aluminum transfer in the cylinder, it is easier to get to the transfer in a bolt-on cylinder also since the height of the clamshell design cylinder is greater. I recently did my first bottom end (crankshaft bearing replacement) work on a "pro" construction saw, and I have to say, I would rather work on a clamshell if crankshaft bearing replacement is being performed. I don't have any special tools to split the crankcases or anything, but I found it significantly easier to swap bearings on clamshells than it was to do that in a saw with "pro" style split crankcase design.

I rebuilt an MS-250 last fall that had failed crank bearings. The plastic bearing separators had disintegrated as Okie warned about earlier in this thread...

Look at your bearings really close and if they have the plastic bearing separators replace them with ones that are all steel before they start crumbling.

Clamshell engines seem quite out of favor to most on this board, but for me, I don't mind working on them at all.

 

[NCPT]

I noticed the little plastic separator in the crank bearing was cracked....so I decided to replace them after all. I can't get the inner race off!!! Tried heating and prying, clamping the race in the vise and tapping the shaft....now it's in the freezer and maybe add heat with a torch after it comes out.

How easy is it to damage the crankshaft with my approach? My 2 jaw puller just yanked the outer race off and the inner race is so close I can't get anything behind it.

 

[Okie]

That sucks:

I have a heat gun that looks simliar to a hair dryer that I can direct the heat towards a bearing or part.
I warmed the bearings trying to direct the heat so as the bearing race heated faster than the crank and the bearings pulled off easily using a two jaw puller and a small bearing separator.
To install I first placed the all metal Nachi bearings in a oven at 170F and the crank in the freezer for about 30 min and wiped the crank with a ATF oiled paper towel when it came out of the freezer and the bearings pushed on by hand and were tight when all came to same temp.
On the clutch side I cut a thin piece of plastic (like a shim) around the crank so as the new seal could be slid over the clip groove and not damage the new seal's lip.

Your bearings rollers must have been worn out to come off without the race.

Just a thought:

Instead of using a two jaw puller you might try a small bearing separator (type that is threaded that use's the two puller bolts and a steering wheel type puller. (slotted type puller instead of jaw type) Might have to grind a slot (notch) in each side of the race for the separator to get a good bite.
Warming the races might help.

Separator and puller looks something like this using the small one.
https://www.ebay.com/itm/12PCS-bear...Tool-Kit-New/201529115463?hash=item2eec124347

Wear safety glasses when pullling or pecking on those, a race chip can break off and easily put out a eye. Most people don't think about such until it's already happened.

 

[Okie]

another thought:

If you can find a tip for a propane torch that has a pencil tip flame. You can direct the flame so as the race is warming faster than the crankshaft.

The torch will look like this and connects to a small disposable propane cannister.

https://www.amazon.com/BernzOmatic-Basic-UL2317-Pencil-Propane/dp/B00008ZA0C

 

[NCPT]

another thought:

If you can find a tip for a propane torch that has a pencil tip flame. You can direct the flame so as the race is warming faster than the crankshaft.

The torch will look like this and connects to a small disposable propane cannister.

https://www.amazon.com/BernzOmatic-Basic-UL2317-Pencil-Propane/dp/B00008ZA0C

That's exactly what I'm using. It's been in the freezer all last night and today. Just put it in the vise and applied heat from the torch.....nothing. I really don't want to have to cut these off.