STIHL 1127 Series Complete Engine (029, MS 290, MS 310, 039, MS 390 Chain Saws)

[D'Animal]

This will be a pretty complete and step by step procedure to disassemble and reassemble the chain saw.

All the saws in the title have the same chassis and are built the same. A few parts are different such as the ci of the cylinder and piston as well as the oil pump. Visually, they are the same.


Depending on what you are repairing on the saw, some steps may be skipped. For example, if your are repairing the starter, not need to take the bar and chain off, etc.

 

[D'Animal]

The saw.

 

[D'Animal]

Remove the Side Cover and Guide Bar and Chain.

Remove the sprocket and clutch assy as outlined here:

https://forum.ih8mud.com/workshops-...-removing-inboard-clutch-stihl-chain-saw.html

Next remove the side cover on the chain brake mechanism. Some may be a plastic cover, this is a newer one that is magnesium.

 

[D'Animal]

Here is how to diassemble the Chain Break Assy for cleaning, inspection and maintenance.


Disemgage the chain brake (pull back on the handle) and remove the big spring before you start.

 

[D'Animal]

Remove the screw and retaining cup on the starter side of the saw. You cannot get the hand guard off until you remove the screw on the starter side.

Remove the brake band itself.

The black hand guard and the eccentric arm come off together.

Do not loose the little spring that hold the tensioning arm.

 

[D'Animal]

These slide off together.

 

[D'Animal]

Remove the starter assy.

 

[D'Animal]

Remove the black handlebar.

It has a total of 7 screws holding it on. First you have to remove the 3 expansion plugs.

 

[D'Animal]

The last two screws are under the the saw on the bottom of the rear handle.

Handle bar removed.

 

[D'Animal]

Remove the muffler.

These locking nuts get kinda tight.

Don't loose the flat washer behind them.

The sequence should be.

Nuts
Muffler
Gasket
Heat Shield
Bolts

 

[D'Animal]

Next is the intake side of the saw.

Remove the airfilter assy.


Squeeze the throttle trigger and you will see where the throttle rod attaches to the trigger. It just pops off with some help with a pair of needle nose pliers.

 

[D'Animal]

Remove the nuts and filter base plate (if your saw has one).

Disconnect the fuel line and the craburetor will pull off.

 

[D'Animal]

Now for the wiring. Look at how it is routed before you start removing it.

You have two wires. The green one is the ground wire and has a regular spade connector. The balck wire is the kill wire. It comes out of the master control switch to the left as shown.

 

[D'Animal]

With the carburetor removed, slide the carburetor base plate and gasket off of the studs. Gently push the intake boot (big black rubber thing you are looking at) through the orange housing towards the engine.

Gently push the wiring and wiring grommet through the orange housing towards the engine.

Remove the front expansion plug near the muffler. There is no screw here, just the plug.


Remove the orange housing.

 

[D'Animal]

Here is what you will be looking at.

 

[D'Animal]

Remove the flywheel. There is a special tool for this. It is called a knock off tool.

Screw it all the way down and back it off one turn and give it a smack with a little hammer. It jars the flywheel loose.

Don't beat on the crankshaft or pry on the flyhweel. You will destroy and break things.

 

[D'Animal]

Remove the two screws holding the ignition module down and remove the module.

Remove the four screws big screws on the bottom of the engine housing. They are about 3 1/2" long and will be tight to break loose.

Your rear guide bar stud is an engine mount. You will need to remove it. It is tight since it is installed with locktight. You could use a stud remover like the top two pictured. The easiest is to use good old Vise Grips.

Once the 4 screws and 1 stud are removed, slide the modular engine out of the engine housing through the flywheel area.

 

[D'Animal]

Top Picture shows the area that the stud screws into.


Bottom picture is the modular engine removed.

 

[D'Animal]

On the flywheel side of the cylinder will be the series number as well as the model number. This saw is an 1127 series and is an 039.

 

[D'Animal]

From here you can remove the bottom pan of the engine and the crankshaft, main bearings, crankshaft seals and piston assy all come out together.