HOW TO: rebuild your starter motor (and eliminate Hot Starting problems)

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yukonerdave

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If you've never had an issue starting your 'Max, count yourself lucky, cause it SUCKS. I gather that there are numerous possible causes (weak charging system, the notorious crimp, cracked coils, poor grounds all around, weak battery), but it seems that sooner or later the starter itself is going to need to get checked out. The unit is sealed tightly enough that as the brushes wear down everything gets covered in dust and the ground connections within the starter start to fail. Rebuilding it is not especially difficult, and it may just get you back on the road.

I'm using an older model 2-brush starter but I assume that the newer 4-brush models suffer from the same problem, and will come apart the same way.

First things first, disconnect the battery (learned this the hard way). Remove the faux cover, the right side scoop, and the radiator cap

We're going to drain the coolant and remove the radiator in order to get easier access to the starter. I'm sure its possible to do it without removing the radiator, but you do need to displace hoses in any case so you're going to want to drain the system anyway. I found that getting the radiator out of the way entirely took an extra 2 minutes, and just helps you to see what you're doing. Start by turning the draincock so the little ball sits in the bottom hole. Then remove the main drain bolt under the water pump. It will pour out fast once you pull it so be prepared. If you haven't changed your coolant in a while this might be an opportunity to flush the system and get some new coolant anyway. I just changed mine, so I will keep it in a clean bucket and reuse it:

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The starter is behind the radiator hoses. I removed the side covers on the radiator (two screws on each side), and then removed the bolts holding the radiator to the frame:

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Figure out which hose clamps to loosen and pull them off, being prepared to catch more coolant. I caught most of it in the wife's measuring cup (oops), and the rest soaked into her bathroom towel :clapping::

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You'll also want to remove the horn. Two bolts on the bottom bracket, and the wires just pull off:

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With the horn and hoses out of the way you are ready to remove the starter. It is held on by two bolts (in red), and you can also remove the power cable at this point (in green):

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Next part is a little tricky. You can pull the starter towards the right side of the bike to disengage the teeth from the gears. At this point it is going to seem like you need to remove the thermostat to get it out, but with just the right wiggling and manipulation you can work it out without removing anything else:

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Alright she's out and ready to to be disassembled. Two long bolts hold the case together - take em out (helps if you have a dog to grab your tools):

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Pull the top cap off, and remove the ridged washer and three spacers:


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Now you can pull the unit out of the case and set it aside:

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The bottom cap will also pull right off. Under it there is a thin plate with the brushes mounted on it. The plate is wired into the main case:

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These three tabs are the culprit. The contact three corresponding bumps on the inside of the bottom case, and that is how the power going to the starter is grounded. As they get caked with dust, you lose grounding. Start by removing the brush plate from the case by taking out the screw holding the wire on:

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Might as well take the opportunity to inspect your brushes. I had new ones anyway, so I exchanged them. Here's the difference between old and new:

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Basically what you want to do now is ensure that you are getting a good solid connection between those tabs and the corresponding bumps on the interior of the bottom case. I used a dremel to take them down to bare metal, and also bent the tabs slightly so they would be pressing against the bumps when I reassembled everything:

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That's about it. I know others have actually soldered a wire directly onto the brush plate and then drilled a hole in the bottom case to attach the ground wire to a small screw. I'm hoping that what I've done will be enough but if I need to do this again I'll consider doing that. I used brake cleaner and the wife's toothbrush to clean all the dust off of everything. Putting the unit back into the case is a little tricky - just push the brushes back against their springs to allow it to sit properly. I imagine this is even more tricky with the 4-brush models:


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Note the alignment marks on both the top and bottom cases to line them up correctly:

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Also apply a little grease to the bearings on either end before re-assembling. I believe that there is a rebuild kit with new brushes, washers, spacers, and O-rings - check all of those before reusing them. Once it is back together, make sure it spins before reinstalling it on the bike. Just hold it in a clamp, run a jumper cable from the negative terminal of your battery to the starter case, and run the positive to the terminal bolt (I used a jumpstarter instead):

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Assuming it spins well, it goes back in the way it came. Make sure all the radiator hoses are attached and clamped before refilling the coolant. Also take the opportunity to inspect your starter wire - I removed mine and upgraded to a thicker one. At the very least, take a wire brush to the connection and the terminal on the starter. That's it - fire her up and listen to her growl!

***EDIT - Starts like a F***in CHAMP now, both cold and hot! This is a great fix if you've got starting problems***
 
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Well done Dave! Great pix, great instructions, love it. :worthy:

You're inspiring me to finally do the valves job write-up. And I have the time to do it now too!

One question tho, I can see why you would use the wife's measuring jug, even her towel, but her toothbrush!? C'mon man, don't you have your own? :ummm: :rofl_200::rofl_200:
 
Thanks, Naughty - I'd really like to see the valve write up, BTW

FYI the starter wire comes out very easily and if you bring it in to NAPA they can set you up with a heavy gauge replacement for 10-15 bucks. I went with a 4 ga. and it fit in just right. My original o was actually quite corroded and about half the wires at the starter were frayed right out, so that may have been half my problem.
 
When you are assembling the starter you can put the brushes in after you put the brushbox in place.You can pull the spring back and then slide the brush into place and then screw the brush lead in place.And you should have a look at the positive cable mounting bolt as sometimes they need to be resoldered onto the copper lead from the field windings.Cheers Kevman.
 
VERY, VERY well done Dave!

You've put into pictures exactly what I've tried to put into words in past posts, but I failed miserably. Those three tabs and corresponding "bumps" cannot accurately be put into words. With pictures, this write-up should actually help many maxers do the fix on their own.

Thank you.


I will say though, I didn't take the radiator out, and instead went ahead and pulled the thermostat housing out to get the room to pull the starter. Removing that smallest radiator hose, and getting the thermo housing out was the roughest part of my starter rebuild.

If I do it again, I'll probably follow your write-up instead.
 
Nice writeup Dave,

however, I think these additions would be helpful:

It is not necessary to dismantle neither thermostat housing nor radiator. However, it is a good opportunity to check thermostat operation with hot water and thermometer or replace it.

It is helpful to squirt some oil to where the starter is being pulled from, because the friction between o-ring and dirt in there is what is making it difficult to pull it out.

Commutator copper contats should be deburred and cleaned till the bare copper shows with fine sanding paper, as well as brushes! It is a must when replacing brushes!

Putting rotor back between the brushes is easier, especially with newer 4-brush starter, if you hold the springs back by pieces of sheet metal put between the springs and the brushes' housings.

Ride safe...
 
I cleaned out my starter motor following the step by step photo instructions, mine is the 4 brush motor, found an easy way to hold back the brushes to reinstall the coil, see photo & insert it in the original post if possible.

Removing the coolant drainage assembly (just one Alan head screw) made room to remove & install the starter motor with ease, the side of the assembly closer to the screw has an orange O-ring so watch out for it.
 

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I'm so glad I looked on here first before tearing my starter out or buying a new. Starter is pulled , cleaned, works great, and reinstalled. Thank so much for the pics and direction.
 
doesn't changing to a heavier starter cable act like a current resister in it self. i always thought the factory used the smaller cable because that is what the current load is.Any thicker, it holds back the full current to the starter.I can understand making better connections thru soldering crimps and changing to a better quality wire.I woud think that going bigger defeats the purpose.
 
doesn't changing to a heavier starter cable act like a current resister in it self. i always thought the factory used the smaller cable because that is what the current load is.Any thicker, it holds back the full current to the starter.I can understand making better connections thru soldering crimps and changing to a better quality wire.I woud think that going bigger defeats the purpose.

No, You've got that reversed Bro. Resistance will increase with too small of a wire. Think of a light bulb filament, in fact put an ohm meter across one. You'll get a resistance reading. Now go across a piece of copper pipe. Zero ohm. Know what I'm saying? Factories spec out the smallest practical wire sizes to save $. Wire is speced. for expected load, heat, and future wear and tear. Wire becomes corroded, strands break, heat raises resistance along with the load placed on a starter. Example-take an amp reading on a cranking starter lead. Now take a reading with the spark plugs removed, cranking. There will be a much higher amp reading with plugs installed. That's my story and I'm sticking to it. There is much more to it, but I like to be brief.
 
I did the rebuild like a year or two ago,it was short lived. I did get a used 4 bush this year, starts strong every time.....I would recommend to everyone to get a 4 brush, it's worth the $$$.

Odd. I did my starter rebuild like about six or seven years ago, and it's still cranking hard.
 
Thanks Yukonerdave, this totally solved my hot start issues! I replaced the old wiring harness with a newer one, did the crimp fix, removed the electrical connectors to the R/R and did a solder job plus direct positive wire to the battery, ran extra ground wires from the battery, and every other fix I could find on this site. All of that improved my charging but the starter still turned super slow when hot. Once pulled off the bike I disassembled the starter and a ton of dirt and dust poured out of it. No wonder it couldn't turn! I cleaned all the connections and event turned the tabs down to make better contact and now the bike turns over fast and starts within 2 seconds. Thanks for the awesome how-to!

Fatbiker
 

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