2001 M750 missing on one cylinder at low revs - Ducati Monster Forums: Ducati Monster Motorcycle Forum
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post #1 of 4 (permalink) Old 08-14-2019, 08:40 PM Thread Starter
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2001 M750 missing on one cylinder at low revs

First post, and i'm new to Ducatis. A lot of experience with 70's UJMs.

I've had this bike for nearly 12 months, and when I bought it I had a local mechanic give the once over. it was running a little rough, and was hard to start. He told me it needed to be run and after giving it some k's it seemed to come good. It had 45,000K on the clock when I got it. I've added another 5k, and it's run well as far I can tell. Quite different to an inline four, but never low on power anywhere in the rev range. The clutch that everyone complains about is way easier to handle than the cable operated clutch on my GS1000.

Recently it started to miss on one cylinder at low revs, and would take a while to warm up. Last week it started to misfire on one cylinder at anything below around 4k rpm.

I've done all of the ignition system checks that you can do with a multimeter. I pulled the plugs last night and they were very dirty, black and a bit oily. I have cranked the engine a bit without starting it. They were NGK DCPR8E. I'd bought some NGK BRP8EA-9 on the basis of reading recommendations on this forum.

I've also got some new belts that I'll fit, and I might even have a go at checking the valve clearances. That looks interesting, although not as much of a pain as the shim under bucket on my z650s!

Assuming that the ignition system is okay, I'm assuming that I'll need to pull the carbs next and at least give them a clean. Anything else I should be looking for or aware of? It's running a stock airbox with a K&N filter. Staintune cans on low exhausts.

Thanks for any suggestions.
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post #2 of 4 (permalink) Old 08-16-2019, 11:21 PM
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I have a 2000 model 900ie,
yes, a bit different from carb models but suffered the same problem with fouling plugs.
you say plugs black, sooty and oily (probably wet) a sign of over rich mixtures.

I experienced about 3 months of this misfire issue, replaced plugs with standard ones and it was fixed.
For about 3-4 hundred klms, then fouled again. Always plugs were black and wet looking.

I work on modern cars, plug gaps around 1.1mm, but early Ducati's say set gap at .6mm. This tells me coils are weak and hence plugs are prone to fouling. I did fix by tuning the TPS etc. and correcting the mixture, no problems since.

In short, before diving in to more complex things, put in new standard plugs correctly gapped and see if it fixes the misfire. If so, then next step is to get the mixtures corrected or it will happen often.

Hope this helps.

Ron.
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post #3 of 4 (permalink) Old 08-16-2019, 11:40 PM Thread Starter
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Cheers Ron. I couldn't help myself and dived in and removed the cars. I figured that there isn't a problem with the ignition so I thought I'd check the fuel side of the equation.
Short story; I don't think the cars have ever been off, and they were pretty filthy. Loads of sediment in the float bowls and some evidence of water in the fuel. I'll be draining the tank now.
Hopefully I'll get a rebuild kit next week and renew the gaskets and o-rings and get it back to a decent starting point.
I suspect this is a build up of small issues that has led to the misfire.
Being used to 4s, I'm hoping tuning 2 carbs will be a little easier.

And I think some new coils are in my future as well. Perhaps even one of those Ignitech modules.

Martin

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post #4 of 4 (permalink) Old 08-17-2019, 09:54 AM
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I also fitted these coil kits, made a huge difference on idle and mostly slowing and decelerating,
bike was surging and stuttering when pulling up to a stop. Almost like it did not want to slow.
had to pull clutch when stopping, these fixed it some what.

http://www.exactuk.com/ccw-high-output-coil-kits/

Much higher voltage, allowing for bigger gaps on plugs. ie. .9mm
Still have the old 900 ie today, will not ever sell it, like yours, last of the good looking monsters. (my opinion) .

If after everything, it still misfires, then the next thing to check is the pickups on the alternator side, the wires can be tested,(google it) but a common problem with Ducati's. need to remove alternator cover and replace pickups for ignition.
good luck.

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