So in my last couple of blog entries I started talking about troubleshooting the starter system on my motorcycle. I discussed replacing the battery, the solenoid, and testing the starter motor. I found that the starter motor was smoking when I had it hooked up to the rest of the system, but disengaged from the starter clutch. As such, my next task was to disassemble the starter motor and see what I could do to finally get my bike running.
Disassembling the Starter Motor
end of it that sets in between the two small gears depicted in this video.
When the motor spins up, it rotates the two small gears which, in turn,
rotate the plate to which they are affixed. This plate is connected
to a mechanism in the front of the motor that drives the primary
engagement gear of the starter motor.
The disassembled starter motor is depicted in Figure 2. You can see the armature set to the left side of the picture. The golden end (copper) is the end that makes contact with the brushes. The brush assembly, mounted to the aft ring, is in the center of Figure 2. The failed gasket, mentioned above, is in pieces next to the armature. The gear assemble is set in the upper right hand corner. The rest of the pieces are simply housing components and washers.
Cleaning
Figure 3 also shows the remnants of the failed gasket which I had to replace. Now, it is important to note that, when working on vintage motorcycles, finding specific bits and pieces is not always easy. If you have a local vintage bike dealer, this can make the experience somewhat less painful. However, trying to locate such a specific gasket online is next to impossible. As such, I resorted to cutting my own gasket which will be described later.
with the two arrows pointing at the filthy
brush heads. Notice the small torsion springs
in between the two brush heads. These
springs push the brushes forward so
they contact the armature at all times.
Now, the repair manual instructs the mechanic to clean the brushes gently with a soft, plastic brush and a light solvent, so as to not damage the wire coverings. I couldn't get the caked gunk off the brushes with a plastic brush, so I got creative. Did any of you do the experiment in third grade where you clean a copper penny in vinegar (a light acid) with a 9 volt battery? The current provided by the battery (supplied to the vat of vinegar via two wires) helps move the ionic, acidic solution (isn't chemistry fun) and scrubs the penny down to the bare copper.
I decided to do a similar set up to insta-clean my brushes. Now, I want to make it clear that YOU SHOULD NOT TRY THIS AT HOME unless you are willing to burn down your own house. My rendition of the penny experiment was to drop my entire brush assembly in a plastic bowl full of vinegar. Then I took an old extension cord, cut one end off, separated the two internal wires, and dipped the two free end wires into the vinegar. Then I plugged the extension cord into the wall. Again, this is an extremely dangerous set up and should not be replicated. The only reason I did it was because I am reckless and cocky. So please, I beseech you, do not duplicate such a setup.
All danger aside, however, the experiment worked beautifully. After 5 minutes the vinegar was literally boiling, and there was a film of blackened crap sitting on the surface of the liquid. When I fished the brush assembly out, all of the copper, steal, and aluminum was literally shining. I cleaned the remainder of the motor housing with alcohol and paper towels. All I had left to do was replace the failed gasket and reassemble the motor.
Reassembly
cut, II pinned the resulting circle to prepare
for the inner diameter cut.
to replace the failed one.
Either way, I had enough parts to reassemble my starter motor. This was a bit tricky, as I was left holding together the three pieces of the assembly (gear, armature housing, and aft brush assembly) with one hand, while trying to thread the two long screws with the other. With some patience, and well-thought out, perfectly articulated expletives, I got my motor assembled and ready to run. I should mention, I did need to re-lube the small gear on the end of the armature (that contacts the other two gears in the assembly shown in Figure 1). With the motor assembled, it was time to hook stuff up and test it out.
Solution
So, I started installing the clean starter motor. This was done in reverse of the steps discussed in my previous blog. Unfortunately, in my excitement, when I was tightening down the banjo bolt that holds the oil pump line in the correct position, I over-torqued the bolt and broke it off. I was furious. Here I was, with a nice, clean, fast starter, and I broke a bolt. Well it turns out that particular bolt is not a generic bolt. That bolt has a hole drilled in one end of it, as well as a hole drilled through it's shaft (perpendicular to the shaft). These two holes form a 'T' inside the bolt itself and allow oil to be pumped up from the case, through the oil line, into the cam assembly on top of the engine. Without this bolt, my bike wasn't going to be running.
So, I spent a week chasing down a replacement bolt for my bike. At one point, after having been told it was called a banjo bolt, I got the Harley Davidson shop in Santa Maria to order me the right part. I waited a few days and, when it arrived, I found the replacement bolt had three holes in it instead of two. It was the wrong part. Exasperated, I jimmy-rigged a solution using a nut, a washer, and some gaskets (essentially, I just blocked the extra hole and hoped oil would find it's way into the oil line one way or another).
With my new jury-rigged get up, I hooked all the electrical back up (starter, solenoid, etc.) and hit the starter button. I was granted with a brief chugga-chugga-chugga of the engine before I heard that damned ominous click again. The starter still didn't have enough torque to keep the engine turning. Exasperated, I started calling local shops looking for a replacement starter motor entirely. That's how I stumbled upon Joe Brown in Paso Robles. His shop recycles and repairs dozens of models of Yamaha bikes, both modern and vintage. He assured me he had a motor that could turn a 750 engine, so I headed up north to buy it off him. Luckily for me, he also happened to have a few of the right banjo bolts on hand to replace the one that I broke. Well, it's always good to have spares, so I bought a few new bolts along with my motor and rushed home.
Once home, I put in the motor, installed the new bolt (carefully), and tried the starter switch again. With a sharp whir and a healthy roar, my motorcycle woke back up from her month long slumber. Giddy as a schoolgirl, I jumped on, pulled my helmet on, and took her out for a short ride up and down the street in nothing but my shorts and a tank top. I was back on the road. =D
Lessons Learned
However, I also learned to trust my own knowledge. My first tests showed me that the battery and solenoid were good, and the starter motor was probably the problem. I ignored those tests in hopes that life would be easier just by replacing the easy-to-get-to parts. Of course, I was wrong. Those tests are useful for a reason, and to ignore them outright was sheer silliness on my part. I guess what I really learned was that it is important to ignore my own bias in favor of reality. If my tools are measuring a certain kind of data, ignoring that data won't help me. That data is what it is for a reason, and learning to interpret it, rather than ignore it, is the first and most important step of maintenance I think.
Finally, I learned to be gentle on bolts. Not every bolt is meant to be cranked down. Thus, even if you think a bolt is very important for your machine, only tighten it as much as is necessary, otherwise you risk turning a final step into a whole new repair, which is a gumption trap all on it's own.
So that's about it for now. I will have some new projects up soon, as well as some new additions to my website in general. I hope this proved helpful or educational to someone. So, until next time,
Best of Luck, and Rock On!
Brady C. Jackson
nice writeup. it gave me the confidence to pull my starter motor myself and diagnose my solenoid.
i noted that the diagram in the haynes manual actually had the gasket on the wrong side of the plate that separates the gears from the armature.
i ended up rebuilding my starter with a kit, using only the brush assembly and gaskets. i used brake cleaner to clean all the gunk out, which was still there despite my gaskets being intact.
i was worried about buying a used starter from ebay because i didn't know what condition they would be in inside. i couldn't find any new or newly rebuilt ones. one guy was selling one that claimed it was good, but it had obvious dings on the outside from somebody hitting it with a tool to try to get the starter to fire. on a bench, as you found, even an almost-dead starter will spin.
as you probably figured out from installing the new brush kit, the old brushes get so destroyed & short that the springs no longer push them effectively on to the armature. and all of the little grooves in the copper end of my armature were obviously filled with crap, which i scraped out gently with a small screwdrier.
anyway, thanks again for the writeup. my bike starts with authority now!
simonster
78 xs750 cafe w/ 850 motor.
Howdy Simonster,
I'm glad you found the walkthrough/tutorial helpful. I know that tearing apart any complicated assembly on a bike can be intimidating at first, but you have to remember that until someone fixes it, you're not going to be riding. That said, keep up the good work on your own bike. A little bit of maintenance will go a long way.
I know brake cleaner works great as an all purpose solvent. It's just too bad it can get so pricey. I use that stuff to clean just about everything. I am glad you got your starter working and I am glad your bike is running. About a month after finishing this repair, I laid my bike down on an onramp and I have been stitching up the cosmetics on her ever since (no engine damage thank heavens). I can't wait to get riding again myself.
Anyways, thanks for the comment and I am glad it could be helpful. Feel free to follow the RSS feed, or bookmark my site or whatever. If you have a blog or a website, send me the address and I'll link to it from here.
Best of luck,
Brady C. Jackson
Nice write-up. Kudos on your willingness to dig in and try things out before buying something off the shelf. I realize it's mostly a moot point now, but something that occurred to me was that you likely could have still used your bike temporarily by bump-starting it. Something to keep in mind for the future, for if or when you're stranded with a weak battery or the starter clutch misbehaves or whatever.
Howdy Alexey,
Thanks for reading through my write up. I actually was bump starting the bike regularly before I started fixing the starter. In fact, the starter quit out when I was in the middle of nowhere on a ride in the hills, so I had to roll start it a couple times just to get it home.
It was kind of funny, actually, a cop offered to help push start me, but since the bike is so heavy (being old and such) he couldn't get me going fast enough to turn it over. So I asked him to help me push the bike up a nearby hill, but he didn't want to go through the effort. He told me he'd call in a squad car with jumper cables. In the meantime, I pushed the bike up the hill myself, which was no easy task, pop started it on the way down and just rode off leaving the cop there on the radio. :)
Best of luck Mate,
Brady C. Jackson
Hi Brady,
you did that work well and most of your'e explains are right ... if i understand youre words to 100% :-)
Pleas think about the Bearingbush at the collectors side - somtime the rotor scratch/slide on the inside of the stator, bcause of that 9mm bearingbush is growing to ~9.5 ore more!
Thanks again for this. It turns out that my starter had the -exact- same issue as yours. I am now also looking for make my own gasket, and I was wondering if it was somehow, against all odds, possible that you might know the exact dimensions of the gasket?
Awesome writeup. It's by far the most detailed and thorough diagnostic and repair writeup I've seen online. I have a 79 XS750 Special and I have very similar issues as yours. I can start the bike but only intermittently. The starter turns a few times but then starts the same clicking noise you mentioned. I went through the same steps as you to test and I am now awaiting a replacement starter motor. I have my fingers crossed!
Heya Arthur!
Glad you found it useful, but I'm sorry the repair didn't work. Hopefully that replacement motor gets you riding again. Right now my Yamaha is registered non-op in my garage as I work to fix some issues with the front suspension. Hopefully I can get moving on it again soon, because I really like that bike, but my jobs keeping me pretty busy.
Anyways, good luck, and ride safe!
Cheers,
Brady C. Jackson