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Old 11-Feb-2011, 02:06 PM
weeksyracing weeksyracing is offline
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749, really just doesn't quite run right.

Been firing up the 749.

It's a tricky tricky bugger to start. Try any fast idle or touch the throttle and it dies instantly.

Read a thread on starting them and states "don't use fast idle until it starts".

Literally i have to wait until it's ALMOST there just fractionally before it's ready to die and touch the idle on a tad.

Once started it will not really tickover until over 50 deg on the display. When you rev it, it doesn't exactly sound crisp and nice, over about 4000rpm it seems a little better. But also can just cut out when revved and then allowing the rpm to drop completely.

Bike is running a cored set of cans and Akra ECU. Debating swapping the ECU out for standard just to see... Any thoughts ?

Both headers seem good and system is blowing warm from both exhaust outlets.

Sadly due to having a bent gear lever i can't take it for a test ride.

Thoughts appreciated
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Old 11-Feb-2011, 02:16 PM
weeksyracing weeksyracing is offline
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Well blow me..... did more checking and it's running only on 1 cylinder. The front cylinder and exhuast are stone cold even when the rear is red hot.
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Old 11-Feb-2011, 02:32 PM
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I was going to say that this is sometimes a TPS problem, but you've found it's obviously an issue with the front cylinder - could be somewhere along the spark (coil / lead / plug) but it's also a common problem with the 5.9M ECU as well.

As you've got a spare ECU I would say swap it over and see if it runs with that first, as it's a nice easy way to check.


I'd rather die peacefully in my sleep like my Grandfather,
than screaming in terror like his passengers.- Jim Harkins

Ducati 748S | Ducati Hypermotard 1100S | 600-620SS DesmoDue Racebike #111 <-- Sold!! | Avanti Race Parts
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Old 11-Feb-2011, 04:06 PM
weeksyracing weeksyracing is offline
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Well swapped teh coil sticks over and still exactly the same symptoms. Front cylinder ice cold, rear cylinder hot. So, basically it's not the coils, so looking either the spark plug or the wiring from coil connector up to the loom. Obviously the simplest place to start on this is the spark plug so...



What size/config is the spark plug spanner i need ? Same as a 916 ?
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Old 11-Feb-2011, 06:24 PM
weeksyracing weeksyracing is offline
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Got a plug spanner from a mate, fits the plug... but no good on the hole etc... I assume it's a little too fat.



So i'm kinda stuck until i hear back from Skids who'll have one.
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Old 11-Feb-2011, 07:35 PM
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Yes, common problem - the walls of the plugs spanner are too thick so you need a thin-walled box-spanner type. Usually one in the toolkit...



I'd rather die peacefully in my sleep like my Grandfather,
than screaming in terror like his passengers.- Jim Harkins

Ducati 748S | Ducati Hypermotard 1100S | 600-620SS DesmoDue Racebike #111 <-- Sold!! | Avanti Race Parts
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Old 11-Feb-2011, 07:57 PM
weeksyracing weeksyracing is offline
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Well first thing to try tomorrow as i may not have a plug spanner unless i hear from Skids is to swap the ECU.

I'm trying to think if when it was running the other night if it sounded 'right' at all.. but to be honest i really don't know. Would love to get to the bottom of it but until i get a plug spanner i'm a bit stuffed.
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Old 11-Feb-2011, 09:23 PM
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Can you not swap the ecu over now and see if it runs both cylinders?


I'd rather die peacefully in my sleep like my Grandfather,
than screaming in terror like his passengers.- Jim Harkins

Ducati 748S | Ducati Hypermotard 1100S | 600-620SS DesmoDue Racebike #111 <-- Sold!! | Avanti Race Parts
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Old 11-Feb-2011, 09:26 PM
weeksyracing weeksyracing is offline
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Quote:
Originally Posted by antonye
Can you not swap the ecu over now and see if it runs both cylinders?

No mate, dark and no lighting. Also my little fella is asleep. Believe me, if i could see, i'd have swapped the ECU out an hour or two ago, but by the time i'd been out bought a new plug, borrowed the plug tool (that doesn't fit) and tried that... Darkness was upon me.

I then had to read the workshop manual as i didn't have a clue at the time where the ECU was as i knew it wasn't under the seat... but didn't know where it actually was or the process to remove it.
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Old 11-Feb-2011, 09:28 PM
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Flooding

The problem is that the bikes with shower injectors, like the 749/999 series, are very easy to flood on startup - especially when it's cold out. If the plug in one cylinder gets flooded, it often doesn't fire until the engine is heated up and the fuel is being more easily vaporized.

http://www.ducatisportingclub.com/im...leederBolt.jpg

Iridium or platinum plugs with larger gaps can help with this problem.


Platinum and Iridium Spark Plugs


Regarding the use of platinum and iridium spark plugs in a Ducati:

Platinum or iridium plugs will give you worse performance than a conventional plug unless you use a larger gap than is recommended for the steel electrode plug equivalent. One by-product (and benefit) to having platinum or iridium as an electrode material is that the harder material erodes more slowly and consequently allows you to reduce the size of the center electrode and still have a long-lifetime plug. Re-gapping is infrequent or eliminated. In fact, the initial reason this type of plug was developed was an attempt to meet the 100,000-mile durability/maintenance requirement mandated by the US EPA for exhaust emissions, not because they offered any improved performance over conventional electrodes.

A smaller electrode, however, will arc at a lower voltage. This is good because the lower arc-over voltage is not as demanding on your less-than-new ignition coils and wires so the firing is more reliable. But this is also bad because a lower arc-over voltage presents a weaker spark kernel (lower arc current and duration) that is less likely to light off the air/fuel mixture.

Consequently, dyno testing shows a performance gain with specialty plugs only when their intrinsically lower arc-over voltage has allowed users to increase the plug gap above that possible with conventional steel electrode plugs. A larger plug gap needs a higher arc-over voltage to fire, and a larger gap, combined with good plug wires and coils, will span more fuel molecules resulting in a more reliable burn with fewer misfires. So you get better throttle response.

Not more power mind you, better throttle response.

The transition between throttle positions involves a wide range of fuel/air mixtures and the ability to fire these less-than-ideal mixtures with a minumum of misfires is what throttle response is all about.

When it comes to spark plug gaps, bigger IS better. The larger the spark kernel that is generated by a spark jumping the electrode gap, the more likely and complete the fuel burn will be, and the smoother the engine will run. That is, the larger the spark gap that’s exposed to the air/fuel mixture, the easier it is to initiate combustion. This translates directly into improved throttle response.

Conversely, I have seen several examples of Ducati throttle response problems cured by replacing platinum/iridium plugs that were gapped too small (i.e. the 0.024 in. Ducati recommends for conventional plugs.) Both NGK and Denso pre-gap their Ducati application specialty plugs to 0.035 in. This should be considered a minimum gap for this kind of plug.

If you have a older bike, you may arc-over the plug wires before you can fire an optimized larger plug gap. If the spark plug wires have inadequate insulation, the wire cannot maintain a high enough voltage across the insulation and will arc to ground before firing the plug gap. The factory spark plug leads are stranded wire covered with an EPDM jacket and although the wire itself will last a long time, the insulating jacket will start to break down after a couple of years which is why most good aftermarket wire is insulated with silicone.

If this becomes a problem, replace the stock spark plug wires with a set of Magnecor or similar quality wires. This will allow running a larger plug gap without a concern for insulating the higher voltage needed to jump the gap. Ducati Superbike Magnecor #2549 wires, for example, run $67.

For street bikes, you should use carbon core wires, preferably carbon wires with a spiral wrap center conductor. Straight, multi-stranded, unshielded wire conductors offer theoretical gains resistance-wise, but produce lots of electromagnetic interference (EMI). One major concern is with the computer found used on fuel injected bikes since the radiated EMI can interfere with the computer and corrupt sensor and internal signals which can affect engine performance and reliability. This concern also extends to the use of non-resistor type spark plugs.

For older Super Sport bikes, Dynacoil replacement coils are also available and a recommended upgrade.

Last edited by Shazaam! : 11-Feb-2011 at 09:52 PM.
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