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Discussion Starter · #1 ·
Hello -

I have been having some hesitancy at acceleration and after working on the carbs for a while I decided to pull out the sparks and see what stage they were in. One out of three plugs came out like this - I am pretty sure I did not damage it as I was taking it out because there was quite some carbon buildup where the spark lead used to be. So I am assuming that it has been running like this.

It is hard to believe that the engine could still run like this!.

I am afraid the piece that broke off must have fallen in the engine, I mean there is nowhere else for it to go but straight down onto the pistons right? I am completely puzzled!.

What do I do now? Take apart the engine to look for the broken piece?
 

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I'll second the magnet-on-a-stick idea. See if you can find the flexible kind so you can carefully sweep all around the combustion chamber. Any chance you can beg/borrow/steal a boroscope? That's a fancy little gadget with a light and a fiber-optic view. Then you could actually get a look inside the cylinder. Much peace of mind could be had knowing it's not embedded in the piston crown and waiting to pop out at the worst possible moment (like there would be a good one!)

If you are a lucky monkey the missing part fell off while you were taking the plug out and did not damage anything.

If it was bouncing around, it may not have done anything yet - but I wouldn't want to run it again til I knew that piece was OUT. Wouldn't take any more than that to trash an exhaust valve as it passed through.

On the up-side, I bet the bike runs alot better with new plugs!

Ben
 

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chances are its already passed though the exhaust but running a magnet around in there wouldn't hurt. You can buy a telescoping magnetic pickup device from Sears for a few bucks that would be ideal. If that doesnt retrieve anything then crank it over with all the plugs out and listen to hear if anything is flying around (you'll get a clicking or pinging sound if it is). If you don't hear anything like that I'd assume its gone.

Personally I think its likely way too small to have likely done any real damage such as get wedged in the piston or head. It could damage a valve or seat but you'd likely know by now if it had.
 

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bore scope is the best place to start.check for scoring on cyl.walls,if no scoring and bits passed through exhaust you may be ok. damm,we never see these types of posts on 955i forums.
 

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Discussion Starter · #6 ·
I will get a magnet and check around for it!. It i just crazy that the engine has been running like this. The hesitancy must be a result of this. It started all of a sudden and the consensus was that it has gotta be the carbs - but now that I have cleaned the carbs out and I still have the hesitancy, this explains it all...

The Haynes manual says that I should get the 9 sparks but the ones that came out are 8s.. any comments?
 

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Don't what the 8 or 9 means, but the "reach" of the plug is the length of the threaded part. Gotta make sure that is correct or the top of the piston can hit the plug.
 

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damm,we never see these types of posts on 955i forums.
IIRC First time its been seen on this forum too - if you were trying to imply otherwise...
 

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The Haynes manual says that I should get the 9 sparks but the ones that came out are 8s.. any comments?
I think the 8 or 9 you are referring to indicates the heat range of the plug. I think there was a revision at some point calling for the 8 range. I don't think it's critical. Someone correct me if I'm wrong.
 

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IIRC First time its been seen on this forum too - if you were trying to imply otherwise...
I think he was saying that they don't do that much work on their own bikes in the 955i forums and run to the dealer for every little thing.;)
 

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Seems like you are right there dave I did not recall quite correctly - though at least one of those was a total plug disintegration.

However, my jist still stands - that this is an esoteric failure, and not something we see with any regularity.
 

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You may want to look carefully and see if the electrode was melted or broken off.
The insulator does look very white.
A very lean condition would explain why the hesitation remains with a new plug.
 

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hd002e, Was that sparkplug loose by any chance?

Jim
I seem to recall one (at least) of the other threads recently where this was almost certainly the cause. IIRC as Jimmy said there, a loose plug will not dissipate the neccesary heat away to the cylinder head, with this kind of result. I noticed last time I checked the plugs 1 or 2 were not loose, but a little less tight than I recall when fitting them. A good reason for a periodic check that we might otherwise not do with longer life Iridiums.
 

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Discussion Starter · #19 ·
Hello All,

THank you for your replies -

the plug was not loose - all of the three plugs gave quite a bit of a fight coming out and just out of curiosity I was measuring the torque I was applying when I was taking them out (I just got a new torque wrench :) so I use it on everything now) It stopped clicking at 60 NM. The booklet says that they are to be torqued down to 18NM. Long story short, they were pretty tight in there.

I got a better shot of the plug where the lead used to be - I am pretty sure it was broken off rather than melted off - why would you think that it could have melted off? The rest of the plug seems to be working an intact..

As to the type of plug to use sorry for causing confusion I meant DPR9EA-9 or DPR8EA. The Haynes manual says to use the first and the plugs that came out of the bike are tha latter. What are iridium plugs (I have seen them being advertised but do not know what the difference is or if I should get them.)

I have not put in the new plugs yet - I am a weekend mechanic :) - I will order the part based on what the consensus is and go over to the garage over the weekend and fish around with a magnet on the tip of a stick (tube?). We`ll see what happens..
 

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plug looks like it may have been a tad hot - I would also agree that it looks like it has been running without the electrode.

On the tightness thing, most likely they weren't put in that tight but were dry, so sticking - I usually put plugs in with a small dab of anti seize grease, and do the old finger tight plus a quarter turn or so to snug it - or if you really must torque it - do it somewhat lower to compensate for the anti-sieze. This will make it easier to get them out next time and protect your threads.
 
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