Help a newbie...mechanical issue on recently acquired '99 M750

[motoxmann]

the spark plug caps screw onto the plug wires.  if they rotate easily on the wires, pull them off, cut the end off the wire and screw them on again.  use a lubricant like silicon spray to make it easier.  this is something i often do at service.  replace the plugs too.

always start with the bits you can see.  they tend to be cheaper and it's much less effort.

x2 to this. unscrew, or simply pull the spark plug cap off the plug wire. cut about 1cm off the end of the plug wire, then screw the cap back onto the wire making sure it stays properly centered as you start to screw it on so the terminal actual goes into the wire itsself and not the surrounding insulation. one it screws on roughly 1cm and begins to tighten up, put a new small ziptie around the boot to clamp it to the wire, and try again.

I've found this is almost necessary every 5k miles or so on almost every bike I've ever owned, especially dirtbikes that saw a lot of moisture and vibration

[Saxofoto]

alright, latest update. I've tried trimming the wire with no success. Having exactly the same issue still. A couple mechanically savvy coworkers think that most likely the whole wire needs to be replaced, not the spark plug or coils since current is running through (one also wondered if there's supposed to be a crimp at the end that goes into the cap . I just don't get how the current can go through all the way to the spark plug when it can arc over the air but is shorting out with the cap all the way on. Why doesn't that implicate the cap instead? Wouldn't a short in the wire prevent it from EVER delivering the current all the way across the length of the wire to the plug? I have an appointment at the dealer to do an inspection next Wednesday, which I'll do whether I figure this out on my own or not. If there is an explanation as to how that's physically possible, I'm open to it; I just don't understand it thus far with my limited knowledge. Next thing I'd like to try is swapping the caps to see if the problem stays with the caps or the wires. My concern there is that the horizontal plug works and I don't want to mess that up (could it fray/tear the functioning wire?), but it seems worthwhile. Can anyone shed a little more light on this shorting issue?

[Howie]

The wire itself should be 0 ohms or close to it.  The terminal cap should be 5K ohms + 10%.  If your coil wire is integral with the coil it should be 13.5K ohms + 20%  from the end of the wire to ground.  Keep in mind, since things don't get bad until hot, you need to test  hot or all might test good.

Another way to go about this is to switch parts one at a time until the misfire switches to the other cylinder.

The cap us supposed to screw into the wire so there is no gap.  Oh, you did try new spark plugs, didn't you?

[motoxmann]

I've never encountered a bad cap, nor heard of one, but anything is possible.
if the juice is making it to the cap, I doubt there's anything wrong with the wire itsself, and assuming the cap might be bad is probably a pretty good guess and explanation. so yeah, I would definitely try switching the caps, and as howie said one part at a time until it switches cylinders

[Saxofoto]

So the caps are meant to come off normally? Doing so won't damage a healthy wire? I haven't tried new spark plugs because both are definitely capable of producing sparks under certain positions of the wire.

Just tried switching the caps and the problem didn't switch cylinders. I guess that rules out the caps. Maybe I'll try switching the spark plugs next if I can borrow the right tools. Replacing the wire seems sensible too, just not sure if I have the know-how, but I'll look at the Haynes manual for guidance if I decide to try. Does anyone have a recommendation for spark plugs or new wires/caps? I might locate my own parts in case I end up having the dealership fix the problem and I'll probably save some money and time.

[motoxmann]

correct, the caps are meant to come off normally without damaging the wire, so long as you unscrew them off and dont just yank them off. but you can only do it a couple times before needing to trim the wire again, because the threading of the probe in the cap that goes into the wire will start to damage the wire after a few times. personally I always trim the wire at least a little bit any time I reinstall a cap just to make sure it has fresh wire to connect with

I suggest starting with factory recommendation of plugs: Champion RA6HC, Autozone stocks them, as well as most motorcycle shops. make sure they are gapped to 0.024"-0.025". the plugs with come with large top tips installed on them (cap end), but your bike is meant to use them with the small threaded tips. simply grab a pair of pliers, hold the plug in your hand and grip the tips with the pliers and unscrew them a hair to crack them loose, then unscrew them the rest of the way by hand.
and if at all possible, use a torque wrench to tighten them in the cylinders, torque them to 18 ft/lbs. doing it by hand/feel could be hazardous to your bike's health, as I have actually broken a few of these spark plugs at a mere 22-23 ft/lbs before, and 15 ft/lbs or less is too loose and will often allow the plug to rattle free

[dlearl476]

A couple of points:

If your ignition system is suspect, your can order a pair of Dynacoils from CACycleworks that come with top notch new spark plug wires for around the cost of 1.5-2 hrs of dealer shop rate.
You can buy a case (12) OEM Champions for about the same price as 4 from a local auto parts store from www.sparkplugs.com

[Saxofoto]

Thanks, Dlearl476. That might be the way I have to go. I ordered a couple cheap spark plugs just to try but I doubt that's the culprit here. It seems to be the wire even tho I can't understand how the physics adds up. I talked to the dealership today, and they don't think the wire can be replaced without replacing the entire pickup coil assembly bc the wires are sealed in. Can anyone verify that? It's really annoying that the 50 cent wire can cost $300 to replace as a result of that design, but I guess that's the life of owning a Ducati. I will definitely go the dynacoil route if need be. I want to try to replace it myself, but before I go that route is there anything else I can check (besides spark plugs) to make sure this will solve the problem before I spend $160 or so? What about the ignition control unit? Is that replaced seperately or is it part of the dynacoils? I browsed that site a bit and prices seem reasonable. Thanks again.

[Howie]

The wire is in the coil, not the pick up coil, which is in the engine.  Whether the wire is integral (one piece with the coil) or separate is a mixed bag.  Ducati used both designs in the '90s.  Just see if the wire pulls out.

Also,

The wire itself should be 0 ohms or close to it.  The terminal cap should be 5K ohms + 10%.  If your coil wire is integral with the coil it should be 13.5K ohms + 20%  from the end of the wire to ground.  Keep in mind, since things don't get bad until hot, you need to test  hot or all might test good.

Another way to go about this is to switch parts one at a time until the misfire switches to the other cylinder.

The cap us supposed to screw into the wire so there is no gap.  Oh, you did try new spark plugs, didn't you?

You can buy a cheap meter for less than $25, cheaper than replacing coils as a guess.

[Saxofoto]

This is all a bit confusing, and I was also confused looking at the Haynes manual in this regard. When you say "the wire is in the coil, not the pick up coil..." do you mean the ignition HT coil then? I can't quite picture the whole assembly that's giving me problems. The wiring diagram in this guide isn't making it clearer to me what connects to what. I'm looking at this on CA Cycleworks for visual reference: http://www.ca-cycleworks.com/2vcoils  Are these the dyna coils? What does "dyna" mean? These are ignition coils and not pickup coils, which was the first recommendation in this thread. This seems like a worthwhile upgrade anyway as it appears to smooth out the low end, but would this definitively solve my problem? Would these wires help if mine aren't integral: http://www.ca-cycleworks.com/cr58515 

As for the metering, I'm not really following you. I get what these numbers mean generally, but I don't understand what they mean in reference to my issue. Can I adjust these somehow or is it just to see if I can locate a point where the ohms are out of spec? And as for a gap, the gap I mentioned is the one between the spark plug and the wire's cap that somehow manages to deliver the current to generate a spark and ignite the cylinder (when that gap is closed and the cap is in the proper place is when my issue occurs and I lose the cylinder; I still don't understand how this is possible).

Thanks again for everyone's input.

[Howie]

The coils in question are the high tension coils.  "Dyna coil" is a brand name that is known to produce a better spark than the factory coils.  Chris Kelly no longer sells them, he now sells his own product, "exact Fit Coils", as in your link.  The pick up coils could be your problem, though they usually fail either completely or when hot.  The pick up coils should read 95+5 ohms.  Test them at the 2 pin connector at your ignition modules.

The specs I am giving you are resistance.  Ohms is a measurement of resistance.  If there is too much resistance in a conductor (wire or connection) it needs to be repaired/replaced.  If there is too much resistance or to little resistance in a winding (in your case, coil or pick up)  the part is defective (open or shorted)

If spark plug is fouled increasing the gap (pulling the plug wire off the spark plug a very little bit can increase the available voltage to the spark plug, helping it fire.  If you want to fix this problem by guesswork, plugs are a lot cheaper than coils, a little over $3 a plug at Ca-Cycleworks.

Ignition may not even be your problem.  It can be fuel or mechanical, or even those expensive, pesky ignition modules, bet tested by switching from one cylinder to the other.

Have you considered taking the bike to a local competent shop?  Fixing things by the "shotgun method" can be expensive and time consuming.

Your problem

[motoxmann]

I talked to the dealership today, and they don't think the wire can be replaced without replacing the entire pickup coil assembly bc the wires are sealed in. Can anyone verify that?

it seems the conversation with the person at the dealership had both of you confused, because it sounds like the dealership guy thought you were referring to the pickup coils, which are a completely different part than the current topic in this thread; the ignition coils. the dealership guy is correct; the wires to the pickup coils can not be replaced seperately, they are an integral part of the pickup coils, and that assembly is  like $300. but that is the incorrect part, at least in reference to what we are currently discussing here. the pickup coils may still be at fault, and we've referenced how to test those a few different times, but from what I can gather you haven't tested those yet. that is what I mentioned on the first page, and what the guy a few posts up referred to again. testing the resistance of the wires with an oem spec of 95-105 ohms, which should be done asap to eliminate from being a possible culprit, or determining it to be the actual fault.

the topic at hand here currently/recently though is the spark plug wires and the ignition coils. and as the guy above said, some spark plug wires are integral to the ignition coil, and some are replaceable seperately. I have a 2000 M750, which is identical to your 99. My spark plug wires appear to be replaceable, but I have never attempted to disconnect them from the coils, so I dont know for sure if they are replaceable seperately or not. I would offer to check for you, but I honestly don't know when I'll have the opportunity to do so, so maybe someone else here can be of more assistance in determining if they are in fact replaceable seperately or not.

[bigiain]

My '99 M750 has ignition coils with replaceable plug wires - there's a screw-threaded spike in the hole in the coil that screws into the middle of e plug wire. Like Howie says though, with Ducati in that era, the actual parts that ended up on your bike could be a bit of a crap shoot, the only way to know for sure is to take them apart.

Big

[koko64]

I've noticed that the black coils had removable plug wires and the grey coils had integral wires usually. Depends what Luigi found supplied in the parts box on that days production run.

What color were your coils?

[Saxofoto]

This has shed some light on my frustration. I was definitely conflating the two for awhile, even after I had figured out they were indeed separate components; just didn't know which coils the spark plug wires connected to. I am going to get a meter to check the resistances tomorrow now that I've reread this part of the Haynes. When I dig into the bike a bit I should be able to see if my wires are replaceable. Tomorrow is my day to figure as much out as I can and hopefully at least rule out the pickup coils. I think I want to get the dyna (ignition) coils regardless as that may solve a separate thing I noticed about the bike's jerkiness when starting (could have been this issue in its early stages too). Howie, your last post makes more sense now too, so I'll be checking/replacing the spark plugs as well. It sucks to have an issue so early into owning a bike, one that renders it unrideable, no less. But it's been a tremendous learning experience so far; kind of makes it all worthwhile. I'll report back when I uncover something new. Thanks again, everyone!