2008 GS Starter Rebuild - how do you hold the brushes back?

[msgoodwrench]

I rebuilt the starter on my GS, putting back together now, how in the world do you hold the brushes back to slide past the commutator?? Thanks for any ideas!

 

[UtahPete]

This is what Google replied when I asked the question. I hope it helps...

When rebuilding a starter motor - like the Denso unit found on the 2003 Rotax 990 engine (commonly used in Aprilia RSV Mille and Tuono motorcycles) - getting the four spring-loaded brushes to stay retracted while you slide the commutator armature into place is famously frustrating.​

Here are the most effective methods and tricks to hold the brushes back and seamlessly slide them past the commutator:​

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The Best Methods to Hold Starter Brushes​

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• The Sockets or Plastic Tube Method (Highly Recommended):​

• Find a deep socket, a piece of PVC pipe, or a stiff plastic tube that has the exact same outside diameter as the armature's commutator.​

• Push the brushes back against their springs and slide this socket/tube into the brush holder block to hold them all open.​

• Line up the armature shaft directly against the end of your socket/tube.​

• Smoothly push the armature into the brush holder, letting the commutator slide in as it pushes the socket/tube straight out the other side.​

• The Dental Floss/Fishing Line Method:​

• Tie a loop of high-strength dental floss or fishing line around each brush braid or backing plate.​

• Pull the lines outward to compress the springs and retract the brushes.​

• Tie or tape the loose ends to the outside of the starter housing to hold them open.​

• Slide the commutator into place, then carefully cut and pull the strings out.​

• The Hairpin/Paperclip Trick:​

• If your specific brush plate has small inspection holes or gaps behind the brushes, look closely to see if you can wedge a small, bent paperclip or hairpin in.​

• Pin the brush springs back into a fully compressed state.​

• Drop the armature in and pull the pins out with needle-nose pliers.​

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Pro-Tips for a Smooth Assembly​

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• Bevel the commutator edge: If the top edge of the copper commutator is sharp, it can catch on the carbon brushes and chip them. Use a tiny bit of fine emery cloth to slightly break or chamfer the leading top edge of the commutator so it acts as a ramp.​

• Watch the shim washers: Ensure any thrust washers or shims on the armature shaft stay in their exact factory orientation. They frequently stick to the greasy ends of the starter cap and fall off unnoticed.​

• Mark your alignment: Before you took it apart, hopefully you scribed a line down the starter body. The magnets inside the housing will violently pull the armature to one side as you slide the housing on, which can dislodge your brushes if you aren't careful.​

 

[UtahPete]

Here's a couple of videos that might help

Videos​

How To Hold Brushes in Place for Motor Starters #MechanicTips​

YouTube · Fix iT Rick​

Jan 11, 2026​

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0:37​

Push the brush up using a zip tie right where the spring is at the top to hold it in place. Then, pull the zip ties out.​

Dealing With Brushes - Starter Motor Trick - New Video Sunday Nov 12th​

YouTube · Joel Arseneault​

Nov 11, 2023​

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11:03​

Use a pick to slide the spring up on the pin to hold back the brushes. This prevents damage when reassembling your motor.​

 

[msgoodwrench]

Thank you! I have been working on this all day! Yes, I did mark lines on the case. I tried the fishing line trick but after an hour, it didn't work for me. Finally I thought to use tiny zip ties, that worked. I got it back together, and now after installation it just whirrs, like it's not engaging. Not sure how to remedy that now. Appreciate your time and ideas! I actually did try to move one of the springs up to the back of the holder, but it slipped completely off and I had to then remount the spring!

 

[jzeiler]

Is it spinning in the correct direction? If you get the windings backwards or the brushes 180 out it can cause the motor to spin the wrong direction.