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Starter motor discovery - Taigene vs Denso

Joined Jul 2014
1K Posts | 45+
California
About a year ago, my bike would take several attempts to start, and the motor sounded like it couldn't turn over the engine. The dash would dim and flicker, and require 4-5 presses of the button to start up. It would make awful clicking and clunking noises too. This issue was most prevalent when warm or hot, but the bike was also a bit weak when cold too.

Ducati replaced the motor with a new motor and the bike was fixed - it would fire right up every time. However.... considering it was the SAME part number, I was always afraid it would happen again. And it did, less than 3,000 miles later.. My dealership refused to work on the bike or submit a warranty claim unless I removed my fuel module, which I didn't agree with since it is unrelated. So... what to do? A new motor is $643 from Ducati. I did some research and purchased a used version of the latest starter motor from Gotham Cycles for a third of what they are new. It showed up in 2 days.

Old part number: Taigene 27040127A. Identifiable by black screws.
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New part number: Denso 27040104A. Identifiable by silver screws.
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Based on my symptoms, the motor was drawing too much current, and not turning it into torque like it should. The massive load on the bike's electrical system makes the dash flicker and could make it seem like your battery needs replacement or your cables are not large enough. One person on another forum measured a 400 amp draw from his faulty motor.

Since I like to know how things work and why they fail, I took the two motors apart and this is what I found. The Denso motor is a 2-brush system with a replaceable brush plate, thicker wires, and a finely indexed commutator. It looked fine overall, and when I tested it on the bench it spun freely and smoothly.
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The Taigene motor is a 4-brush system with a riveted brush plate, and more, smaller gauge wires. But here's what I think is the issue. The wires are not fully coated with the yellowish/white insulating material. You can see the wires of the armature look burnt. I am guessing they are shorting out to adjacent wires and weakening the magnetic field that makes the motor turn, and also drawing too much current. This is clearly a manufacturing defect where they did not dip the armature deep enough in the varnish prior to machining.
X25Duuo.jpg


I am pretty disappointed that Ducati continued to use starter motors from this company. I have found things online dating back to 2011 Hypermotard and Monster models using these apparently cheaper motors, yet 3 years later they continue to put them on their bikes instead of the well known, high quality Denso products.

I will be posting up a DIY tomorrow how to replace your motor since I am halfway done with the job right now. It's actually a pretty involved process since you need to remove the generator cover (left side engine cover) to access two bolts on the motor. But it's not that hard and only requires one special tool which can be found on eBay (I made one in about 20 minutes).

I hope this helps someone!!
 
Nice detective work!

Mines just starting to get the stutter - slow to turn over and taking 2 tries every so often. Just installed Shorai battery, too.
 
Wow! Fantastic diagnosis, this is great to all have in one thread. I bought my bike used and the dealer that used to own/service it when it was a demo went out of business, so I had no idea what kind of maintenance or repairs it had. Thankfully I've never had a starter issue in the 7000 miles I've put on it, but maybe that's because it was already replaced/repaired. I read elsewhere to make sure and buy a denso replacement if the starter is bad, this is just a great way to confirm that suspicion.
 
Mine didn't get weak until almost 10,000 miles

Probably varying levels of dipping. My first one lasted 7,000 miles. This second one started showing signs of failure at just 2,000 miles.

Thing is, a lot of motors don't have the yellowish colored insulator, just the red insulating varnish on the wires. So it must also be a substandard quality or too thin.
 
Thanks for this info and the future replacement guide. My starter is good at 12K miles but I'm going off warranty so this will be a nice thing to know.
 
I'm in the same boat as you kuksul, starter was replayed at 9k for the same reasons and they replaced it with the same part which I'm sure will fail in the none too distant future.

Really looking forward to your write up. Thanks man!
 
Hi there,

just tried to assemble my starter again. Is the denso starter shimed on both sides or just on the back? Got a quiet thick aluminium washer here in my box and cant remember if it was installed originaly or just dropped accidentialy into the starter box where i stored all starter parts. Got two thin washer which where installed in the back, where the brushes are. But cant remember if it was shimed at the front.

Thanks for your help!

Cheers from Germany.
 
Did you pull the tank by chance? There's a giant washer where the back of the tank secures to the frame that likes to fall out right before you guide the bolt home.
 
Nope, tank is installed. I will take a picture later. Maybe we can figure out if it belongs to the starter or not.

Here is a picture. The two in the middle are the original shims installed at the back of the starter and the right one ... i dont know. I can hardly believe it belongs to the starter. Can anybody verify that?

Cheers :)
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Did you disassemble your starter?

I can't say I recall seeing any of those parts... They almost look like what you see on the shift linkage?
 
The starter is disassembled, and all the parts on the picture, except the right one, are 100% from inside the starter. I think i will just put it together and leave the part on the right outside ...
 
It's a bit ironic that Ducati designed such a good bike but so screwed up the execution...Denso parts are pretty consistently some of the best parts made, regardless of use, I'm going to be proactive and swap over on my next oil change, thanks for doing this, we'll have perfect bikes before you're done...
 
This thread popping back up reminds me I will probably need to do this soon. Bike starts fine cold but takes a few cranks to start when warm (aka stopping for gas). It's never bothered me too much as it'll fire up after two attempts but I should probably just fix it.
 
I noticed it declining when still on the stock battery. After the Shorai swap, it's been pretty consistent - slow cranking when cold; noticeably better when warm.

It's not the worst DIY job, but I'm worried my starter is fine and I won't notice much difference after.
 
I noticed it declining when still on the stock battery. After the Shorai swap, it's been pretty consistent - slow cranking when cold; noticeably better when warm.

It's not the worst DIY job, but I'm worried my starter is fine and I won't notice much difference after.

If it's better when warm, it's probably not your starter. My bad starter would be great when cold, and barely work when warm. I'm still not sure the mechanism of why that was the case.
 
I am so happy to find this thread! My 2013 Hypermotard 821 is doing exactly as described here. Starts cold but once it is up to operating temperature, it's a PITA to start. I bought a Lithium battery 480 CCA but it seems to struggle more than a regular gel or lead acid battery. I ordered a HICAP SSCDC kit from Motolectric but haven't received it yet. Your discovery makes perfect sense. My question now is I wonder if the shielding can be fixed by liquid electrical tape? I'm going to try that first and post up the results. Thanks again for this awesome thread!
 
I just followed your DIY thread on removing the starter and took mine apart. Same thing! Loads of carbon or burned residue and it even smells like something electrical burned. I was also noticing a puff of black smoke while turning the motor over and over attempting to get it started. I've got the Denso 27040104A on the way. In the meantime, I think I'm going to insulate the wires with some liquid electrical tape and see what happens. The worst is that I burn it up and that's no biggie.


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I think my 2013 821 'Strada starter motor is going the same way. I can't find any suppliers for the Denso version over here in the UK, but ebay is full of versions called ArrowHead which I'm assuming are very much cheaper than anything Ducati supplies. Has anyone here had experience of the ArrowHead?
Thanks,
Nick
 
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