Ms260 Rebuild by a beginner

[Tinkerer Carver]

That jug definitely looks serviceable. I would stick a good meteor piston and caber rings in it, replace the previously mentioned common wear/air leak items of the impulse line, fuel line and intake boot, rebuild the carb and vacuum/pressure test it. This would be a good chance for some basic performance modifications if you were interested like deleting the cylinder gasket assuing it leaves enough squish, advancing the timing, and opening up the exhaust a bit or at least matching muffler gasket and inlet to the exhaust port outlet. And remember it's just a saw and you have plenty of "help"

Since I’ve already ground on this one, I was thinking performance mods as well. I was thinking port match to where the intake boot sits, port match the exhaust, widen the port on the muffler. Also, for the base gasket delete, do you just use RTV? Or could I measure the squish with a new gasket and have my machinist buddy mill off the difference of the gasket? Here is a closer pic of the scored area

 

[Wonkydonkey]

I think you need to get some timing # first, as well as an accurate squish with out the gasket,

As I’ve never got a jug machined I,m not really sure from here, I just know around 18-20 thou is what is wanted for a good squish,

but I,m sure someone will jump in and school me at the same time.

 

[drf256]

Since I’ve already ground on this one, I was thinking performance mods as well. I was thinking port match to where the intake boot sits, port match the exhaust, widen the port on the muffler. Also, for the base gasket delete, do you just use RTV? Or could I measure the squish with a new gasket and have my machinist buddy mill off the difference of the gasket?View attachment 294529 Here is a closer pic of the scored area

I think you’ve got a 44.7mm jug there. If it is, squish without gasket should come in around .017. You may just need a fuel resistant sealant on the bottom. Dirko, Motoseal, Yama/Hondabond, Loctite 518 all work.

 

[Basher]

Since I’ve already ground on this one, I was thinking performance mods as well. I was thinking port match to where the intake boot sits, port match the exhaust, widen the port on the muffler. Also, for the base gasket delete, do you just use RTV? Or could I measure the squish with a new gasket and have my machinist buddy mill off the difference of the gasket?View attachment 294529 Here is a closer pic of the scored area

If you only need a few thou taken out of the squish band at the top of the cylinder you can sand it out by using the old piston, cleaned up and glue sandpaper to the crown, some turning of the piston is required but easily do able. A little scraping after sanding with a wood chisel real tight to the cylinder wall corner will remove any metal missed by the sandpaper.

 

[Tinkerer Carver]

I think you need to get some timing # first, as well as an accurate squish with out the gasket,

As I’ve never got a jug machined I,m not really sure from here, I just know around 18-20 thou is what is wanted for a good squish,

but I,m sure someone will jump in and school me at the same time.

Looks like I will need to make a degree wheel

 

[Tinkerer Carver]

S

I think you’ve got a 44.7mm jug there. If it is, squish without gasket should come in around .017. You may just need a fuel resistant sealant on the bottom. Dirko, Motoseal, Yama/Hondabond, Loctite 518 all work.

So take timing numbers with and without a gasket, figure out the squish, and get some fuel resistant sealant? Also, do you see the scored area in the last pic? It looks like it’s through the plating if my eyes don’t lie

 

[Cooper264]

Just a heads up for everyone thats looking to buy things like comp testers and leak down testers, don't skimp on them. Pay decent money and pick a decent brand. In my early saw days I got a cheap comp tester from harbor freight, cant tell you how many saws I passed over or sold way too cheap because I thought they had low compression... Live and learn

 

[Mastermind]

We are here to help. Personally have done a few of them 026/260’s.

Which parts do you have? Looks like a 44mm top end to me. I’d use that jug cleaned up, you won’t get the same performance from an AM P&C set. Meteor pistons are fine. That broken fin won’t do a thing.

Do you definitely have a carb with 2 adjustment screws? They came both ways, and IIRC only the Zama has an adjustment limiter. Never seen one on a Walbro on the 1121 model.

If you plan on working on saws, a vacuum and pressure testing tool is a must. In general. A small air leak will result in issues with keeping idle stable. You’ll chase it forever.

You are really forced to go through everything because the saw scored in the first place. Invest in a new oem fuel line and filter and a new oem impulse line. Carb needs to be gone through as well, may as well rebuild it in case there is an issue with fuel supply with the carb itself. The screen may be caked with the debris or there may be a metering issue.

The 1121 is one tough little saw. The bearings are oversized and usually last a very long time. If there is no radial play and they look good, you can probably get by with leaving them alone. A case split may be more than you’re up for at this point.

I know it sounds like a lot, but you can do it.

Great post Doc.

Good thread fellas.

 

[stretch5881]

S

So take timing numbers with and without a gasket, figure out the squish, and get some fuel resistant sealant? Also, do you see the scored area in the last pic? It looks like it’s through the plating if my eyes don’t lie

It's really hard to tell if there is scoring until you have all the transfer removed.

 

[Chainmale]

Just a heads up for everyone thats looking to buy things like comp testers and leak down testers, don't skimp on them. Pay decent money and pick a decent brand. In my early saw days I got a cheap comp tester from harbor freight, cant tell you how many saws I passed over or sold way too cheap because I thought they had low compression... Live and learn

Yep, I nearly striped down an 025 of all things to do rings because of the cheap one I first bought. Another time that browsing through these forums has saved me.

 

[Chainmale]

Looks like I will need to make a degree wheel

How do you plan to make your own? I'm all ears. Want to do some beginner port work myself but spent a bit much on tools and saws lately to buy one

 

[Wonkydonkey]

How do you plan to make your own? I'm all ears. Want to do some beginner port work myself but spent a bit much on tools and saws lately to buy one

you can print a degree wheel off the web, then stick it on a round plastic or metal thing, then fashion up something to fix it to a side of the crank.

I stuck it to a circular metal piece, and used a drill Chuck to tighten to the pto side

edit this is the first hit from googling degree wheel and is what I used

https://www.blocklayer.com/degree-wheel.aspx

 

[Chainmale]

you can print a degree wheel off the web, then stick it on a round plastic or metal thing, then fashion up something to fix it to a side of the crank.
Ah, pretty much what I was picturing, they aren't cheap to buy

 

[Tinkerer Carver]

Just a heads up for everyone thats looking to buy things like comp testers and leak down testers, don't skimp on them. Pay decent money and pick a decent brand. In my early saw days I got a cheap comp tester from harbor freight, cant tell you how many saws I passed over or sold way too cheap because I thought they had low compression... Live and learn

I’m with you on the not skimping. What are some good brands of compression testers?

 

[Tinkerer Carver]

It's really hard to tell if there is scoring until you have all the transfer removed.

So take a ball hone to it lightly and look at the possibly scored area again?

 

[Nutball]

If it's a 44.0mm (probably isn't) cylinder it will need a lot of material removed from the squish band to work without a gasket.

Check squish with a thin (.025") piece of solder. Twist it on itself for more thickness if needed.

I have an OTC compression tester. Snap on or a chainsaw brand if available would be good too.

 

[Canadian farm boy]

 

[merc_man]

Whoa.... new avatar. I almost didn't recognize ya.
I was fond of your old one. LOL

Whats an avatar

Sent from my SM-G950W using Tapatalk

 

[Sagebrush33]

Whats an avatar

Sent from my SM-G950W using Tapatalk

It's the pic you chose above your name.
I've always heard and read them referenced to as avatars.

 

[Swizzler]

Welcome to the internet fellas