Spark Plug interval is 18k miles and new plug wires - Ducati Supersport 939 Forum
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post #1 of 16 (permalink) Old 01-03-2020, 07:23 PM Thread Starter
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Spark Plug interval is 18k miles and new plug wires

I had some back and forth with my local dealership, my owners manual and finally Ducati North America.

The owners manual indicates that the spark plugs are replaced at 9000 miles, the Ducati Transparent Maintenance Guide indicates that they get checked but not necessarily replaced at that same interval, and at my dealership their service writing software (provided by Ducati) indicates that they are to remain untouched until the desmo service at 18,000 miles.

According to Ducati North America the service writing software is correct, and both of those documents have been recently superseded but not yet updated on the website.

This is exciting because it essentially moves all of the invasive maintenance (outside of warranty work) to that one big service. Everything else is essentially chain maintenance, oil changes annually, plus periodic fluid changes (hydraulic at 3 years, coolant at 4 years).

Being the anal retentive technician that I am, I insisted that the shop still perform the plug change per the owners manual so that it's documented correctly until the updated documentation is released; the shop was happy to take my money and the tech happy to have a bike on the lift. Today they told me that the plug wires I have installed have a known likelihood to break when disconnected from the plugs and are superseded with a new part number (suffix D is the update, suffix B came on the bike). I wonder if this is the issue that @Triple S was having with his vulcanized HT leads. The updated part numbers are around $60 each, $120 for the pair.

On my 2017 bike, the part numbers according to the parts diagram are
Horizontal head: 67110601B
Vertical head: 67110591B

The new part numbers are listed as OEM installation on the 2020 parts diagram:
Horizontal head: 67110601D
Vertical head: 67110591D
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post #2 of 16 (permalink) Old 01-03-2020, 09:16 PM
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I'd wait for valve adjustment service.

Modern plugs will go forever with computer controlled, liquid cooled, fuel injected engines. Valve service is opportune since the plugs are removed anyway. Labor being a big part of cost.

Has anyone here had a fouled plug?
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post #3 of 16 (permalink) Old 01-04-2020, 12:21 AM
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thank you Psy that is good info
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post #4 of 16 (permalink) Old 01-04-2020, 02:39 PM
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18k miles is quite a stretch. The longer lasting iridium plugs have a general lifespan of 40 000 km's.

Has anyone tried the MAR10A-J plug or an iridium yet? Just wondering what your thoughts are. I expect the MAR10A-J is better for long day journeys.

Last edited by amoslws; 01-04-2020 at 03:39 PM.
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post #5 of 16 (permalink) Old 01-04-2020, 04:42 PM
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Originally Posted by amoslws View Post
18k miles is quite a stretch. The longer lasting iridium plugs have a general lifespan of 40 000 km's.

Has anyone tried the MAR10A-J plug or an iridium yet? Just wondering what your thoughts are. I expect the MAR10A-J is better for long day journeys.
Assume that 10 is a cooler plug than the factory MAR-9? I can only say that I've done maybe eight days riding 350-500 mile each day. Seems to run fine. Have about 11k miles on the bike now.

What benefit is expected with a cooler plug?

Is there an iridium replacement?

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post #6 of 16 (permalink) Old 01-04-2020, 09:35 PM
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Quote:
Originally Posted by psyopper View Post
I had some back and forth with my local dealership, my owners manual and finally Ducati North America.

The owners manual indicates that the spark plugs are replaced at 9000 miles, the Ducati Transparent Maintenance Guide indicates that they get checked but not necessarily replaced at that same interval, and at my dealership their service writing software (provided by Ducati) indicates that they are to remain untouched until the desmo service at 18,000 miles.

According to Ducati North America the service writing software is correct, and both of those documents have been recently superseded but not yet updated on the website.
Yes, we discussed this a while back on the Forum, and the manual is wrong. In fact, we have on the Forum a post of the plugs being pulled at 18,000 and they still looked really good, surprisingly.

Btw, I just had my 9000 mile service done (with 13,000 on the clock), and did not have the plugs replaced.

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post #7 of 16 (permalink) Old 01-04-2020, 09:52 PM
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post #14 at 30,000 km

https://www.ducatisupersport939.net/...rk-plug-2.html

2017 Ducati SuperSport S
2015 Ducati Scrambler
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post #8 of 16 (permalink) Old 01-05-2020, 03:17 AM
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Quote:
Originally Posted by LowRyter View Post
Assume that 10 is a cooler plug than the factory MAR-9? I can only say that I've done maybe eight days riding 350-500 mile each day. Seems to run fine. Have about 11k miles on the bike now.

What benefit is expected with a cooler plug?

Is there an iridium replacement?
The 10 is used in the multistrada, Ducati's touring model, so for long rides it disperses heat better thus keeping a more uniform spark. The monster 1200 also has the 9 like the SS. Both the monster and multistrada are the same engine. I suspect Ducati expect the multistrada to do more miles in a day with its 30L fuel tank.

There are other plugs available with 3 & 4 electrodes but I don't know if there will be any significant improvements to burning performance. The twin electrodes of the MAR9A-J seem to do the job fine but I have not ridden more than 5 hours in a day with the SS, albeit a very fast 5 hours which probably equates to 10 hours of normal spark.
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post #9 of 16 (permalink) Old 01-05-2020, 07:20 AM
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In terms of the ignition cables (coil to plugs) what brand do you suggest. When I planted the 1200 into the SS I had to mix up the cables from a 1200 and the SS. The 1200's coils are twin spark, meaning two plugs per cylinder.
The coils positions are different, using a different bracket, and as such the horizontal centre cable is a bit tight. Been thinking of upgrading them anyway but I'm unsure what's best for a motorcycle.
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post #10 of 16 (permalink) Old 01-05-2020, 08:21 AM
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Magnacor have always been the best rated HT Leads. They may not do a set for your application but you can probably find something to suit.

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