Burnt Plugs

If you need technical information or help with your BOSCH ignition squarecase Ducati 900SS - Darmah engine - post your FAQs, comments & questions here.
DaleMclean
Cucciolo - the Lil Pup
Posts: 20
Joined: Wed Apr 07, 2010 3:46 pm
Location: Swansea, NSW, Australya mate

Post by DaleMclean » Tue Aug 10, 2010 9:55 pm

I've been having fouling problems too. ONLY after running high octane fuel AND lead substitute.
originally the back cylinder fouling, changed to iriidium plugs and all was good UNTIL Shell 98 and Wynns lead substitute :cry: now front cylinder fouls.
Just like youve described, I can clean the lug and all is OK.
I will from now on ONLY run standard ULP and the Wynns.

Drain the tank fill 'er with 91 and Flashlube or Wynns at the rate it says and all will be good again :-D
I survived :-)

DaveDare
Mariana
Posts: 29
Joined: Sun Jan 14, 2007 6:41 pm
Location: Brisbane, Australia
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Post by DaveDare » Wed Aug 11, 2010 4:38 am

Really!!!!

I will give it a go, ready to try anything, but why is this not more a common problem now with unleaded fuel?

I've been battling this problem for 18 months now and it's only just now that I am getting a few people suggesting this.

Don't get me wrong, thank you so much for taking the time to answer, I very much appreciate it and I will give this a go.

I am still a bit sus about the carby though. The fact I need to wind the idle stop screw all the way in to get a rise out of the front pot has me thinking.

Thanks again for the suggestion.

Oh by the way do ya think I could run it without the additive? It does have hardened valve????

DaveDare
Mariana
Posts: 29
Joined: Sun Jan 14, 2007 6:41 pm
Location: Brisbane, Australia
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Post by DaveDare » Wed Aug 11, 2010 4:39 am

Oh and by the way...why only the front cylinder?...could that be the universes way of screwing with your mind?

Dave::

wdietz186
Cagiva Alazzura
Posts: 703
Joined: Sun Sep 10, 2006 5:40 pm

Post by wdietz186 » Wed Aug 11, 2010 12:34 pm

Dave, Running straight unleaded won't hurt anything in the short run and because the standard valve seats are a bronze alloy I don't think the recession problems that affect cast iron seats apply anyway.I've run naked in my 750 for more than a few years and haven't noticed the clearances change much.As for the carb issues are absolutely sure the pilot circuit isn't blocked? The mixture screw having no effect on low/idle speed points to a blockage.What is likely is the idle speed screw is in enough to make the carb draw through the needle jet which will give you an idle of sorts but not a good one.I'm sure the other basics were covered before like valve clearances,vacuum leaks and the like.The big problem is that these machines are getting old and not being used as much so people can often notice something on a ride an think Oh it's just[enter something simple] I'll just do[what worked the last time] and thats that! But often something else has deteriorated along with the original problem and the old fix doesn't any more. Long distance diagnosis is very hard because we can't see,feel, or smell what is going on in addition to the folklore and wives tales that often enter the picture.

DaleMclean
Cucciolo - the Lil Pup
Posts: 20
Joined: Wed Apr 07, 2010 3:46 pm
Location: Swansea, NSW, Australya mate

Post by DaleMclean » Wed Aug 11, 2010 2:50 pm

Dave, initially ( about 18mnths ago btw) it was the rear cylinder, this time it was the front. I only put 2 and 2 together after checking all sorts of things and then finding the (Iridium) plug all fouled, as a last check after all else faild to fix the miss.
I thought the Iridiums had sortd it all, so didn't check the plug 'till last.
I survived :-)

DaveDare
Mariana
Posts: 29
Joined: Sun Jan 14, 2007 6:41 pm
Location: Brisbane, Australia
Contact:

Post by DaveDare » Thu Aug 12, 2010 6:38 am

wdietz186 wrote:...As for the carb issues are absolutely sure the pilot circuit isn't blocked? The mixture screw having no effect on low/idle speed points to a blockage.What is likely is the idle speed screw is in enough to make the carb draw through the needle jet which will give you an idle of sorts but not a good one.I'm sure the other basics were covered before like valve clearances,vacuum leaks and the like.The big problem is that these machines are getting old and not being used as much so people can often notice something on a ride an think Oh it's just[enter something simple] I'll just do[what worked the last time] and thats that! But often something else has deteriorated along with the original problem and the old fix doesn't any more. Long distance diagnosis is very hard because we can't see,feel, or smell what is going on in addition to the folklore and wives tales that often enter the picture.
No I am not sure that the pilot circuit isn't blocked now. Mind you, I have pulled the carbs down to a certain degree and blown out as much as possible with carb cleaner, but now I am thinking I do need to completely strip the carb down and do it properly to be sure. I will do this this weekend. Thankyou for your input, much appreciated, I will let you know.

Cheers Dave::

rwhc80
750 GT
Posts: 174
Joined: Sat May 16, 2009 7:19 am
Location: Melbourne Australia

Post by rwhc80 » Sat Aug 14, 2010 11:23 pm

Dave,

Thought I would chime in for an update, seeing I started all this off.

Like you, I have now changed the ignition boxes over on the ss, and we took the bike out for a reasonably long run last weekend, ( about an hour or so ) without any apparent plug problems. Unfortunately, weather has been crappy here in Vic, so it's hard to get time to test to any decent extent, but early signs are good. Murphy's law though, the Darmah that went along as a backup left as a 900 twin and returned as a 450 single. It now refuses to start and will not give any spark, even after changing coils.

Jesus, do the problems ever end ???

Cheers Rick.
I have desmo disease, I just hope they never find a cure !!!

DaveDare
Mariana
Posts: 29
Joined: Sun Jan 14, 2007 6:41 pm
Location: Brisbane, Australia
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Post by DaveDare » Sun Aug 15, 2010 12:20 am

I my god, that is funny... sorry but I thought the "450" comment was funny. I haven't had a chance to continue testing and checking (carbs etc) but as you say do the problems ever end, well just to make you feel better, when I took the bike for a test after cleaning plugs last weekend the front brake lines erupted and poured brake fluid all over the front guard and sprayed the inside of the fairing...oh well another issue to fix at some point :)

Will keep you updated on progress with front plugs.

Dave::

rwhc80
750 GT
Posts: 174
Joined: Sat May 16, 2009 7:19 am
Location: Melbourne Australia

Post by rwhc80 » Wed Aug 18, 2010 3:27 am

Thanks Dave,

Sorry to hear about the brakes, but at least we can laugh at each others problems !!!

Things are looking up now, a couple of hours in the garage on Tuesday night and a bottle of good red for hydration and inspiration, found the recent new connector block I fitted in the pickup wires had seperated just enough to kill the spark to the plugs. Halleluja !! weather looks good for Sunday, so a big test coming up.

Keep us up to date on yours ???

Cheers
Rick
I have desmo disease, I just hope they never find a cure !!!

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