I borrowed my friend’s Stihl MS180C chainsaw and while using it I broke the trigger.  It wasn’t completely broken, just a piece broke off from the back of the trigger, which interlocks the trigger with the safety button on the top of the handle. I wanted to return it to the same condition in which it was loaned to me so I went to work at fixing it.  I was able to use JB Weld to repair the trigger but in the process of reinstalling it, the trigger/throttle linkage wire came disconnected from the throttle.  You cannot see how to reconnect it without digging into the chainsaw.  Here’s a picture of the broken chainsaw throttle trigger:

Read on if you would like to learn about my Stihl MS180C Chainsaw trigger repair.

Stihl MS180C Chainsaw Trigger Repair

Hardware:

• Stihl MS180C Chainsaw

Parts Needed:

• Stihl MS18C Chainsaw Trigger
• JB Weld (if you are going to fix your trigger)

Tools Required:

• T20 T0rx Bit
• 8mm socket and ratchet

Step 1: Remove the top cover.

It is a lot easier to work on if you remove the top (orange) cover.  It doesn’t even require any tools to remove.  Push down on the choke while lifting up on the cover.

It is hinged on the blade-side edge and once you lift the handle end up, you can simply pull the cover towards you and it will come off.

Here you can see the places on the cover that hook into the body of the chainsaw (one is a post and one is a hook):

Here is where they are seated into the top of the chainsaw:

Step 2: Open up the chainsaw handle.

Lay the chainsaw on the right side.  There are two T20 torx head screws that secure the side of the handle compartment that encloses the trigger mechanism.  I forgot to take a picture of the handle assembled but here you can see the two screw locations and the handle opened up:

Step 3: Remove the interlock spring.

You can pull the throttle trigger straight off the post on which it pivots but it is easier if you first disconnect the spring from the safety interlock.  Simply untuck the end of the spring from the notch in which it is installed:

Step 4: Remove the trigger.

Remove the trigger by lifting it straight up and off the post on which it rotates on.  Here are the pieces:

Step 4: Fix your trigger (optional).

I cleaned my trigger, taped the bottom side to hold it together, scratched the surfaces that the epoxy would touch with the tip of an Exacto knife, and then filled the space with JB Weld.  This is what it looked like when it was done:

I also ordered a replacement trigger off of Ebay as a backup in case my repair didn’t hold.  It has held so far though.

Step 5: Reconnect the throttle linkage.

When I was trying to reinstall the trigger, the throttle linkage became disconnected.  You cannot see where to reconnect it without disassembling part of the chainsaw.  I finally figured out how to reconnect it and here is how:

Step 5a: Remove the throttle body nuts.

The throttle body, i.e the black box that houses the air filter, is in the way of you reconnecting the throttle linkage.  Remove these two 8mm nuts:

Step 5b: Disconnect the choke linkage.

Ss you pull the throttle body straight off, you will need disconnect the choke linkage. Rotate the arm counter-clockwise until the slot lines up with the wire and then lift the wire linkage out:

The wire linkage will pull straight up and out at this point but it is not necessary to remove it.  You can refer to my images above to see where the other end goes if yours comes out.

Step 5c: Pull the throttle body straight off.

Pull the throttle body straight off in the direction the bolts point (the bolts which you earlier removed the nuts):

Here is a picture of the throttle body removed:

Set the throttle body aside.

Step 5d: Reconnect the throttle linkage.

If you put the linkage into place you can rotate it into the fork as shown below:

Here’s a close-up look at where the throttle linkage connects:

Once you have the linkage connected, you’ll need to support it to keep it from disconnecting.

Step 5e: Reinstall the throttle body and reinstall the two nuts.

Slide the throttle body directly on the two bolts and reinstall the two nuts:

Reconnect the choke linkage:

Step 6: Reinstall the throttle trigger.

Feed the throttle linkage through the oval hole and then slide the trigger onto the post on which it rotates.  Then hook the left edge of the spring on the throttle and pull the other end back and slip it into the notch on the right side as seen below:

Step 7: Reassemble the handle.

Put the cover piece back on the handle and reinstall the two T20-headed screws.

Step 8: Reinstall the top cover.

Seat the far edge of the cover and then rotate the near edge down and onto the chainsaw:

You may need to push down the choke button to get the cover to seat all the way down: