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Discussion Starter · #1 · (Edited)
I am having an issue with my 748 (slightly over 9,000 miles), and hopefully someone can help me figure this out.

The bike is not idling properly. Occasionally, it actually will idle, but not it mostly just dies, unless I massage the throttle. Also, after taking the bike out this aftetnoon and shutting it off, it would not restart. The fuel pump spins strong when I switch the bike to run, and the starter is turning the motor, but no start (even when opening up the throttle.) Eventually, it dud fire up, after about five minutes of trying, and ran fine. Then, when I shut it off again, same issue. Any ideas?

It seems to be okay, if the bike is cold, which makes me think it is possibly a coil, but the idle issue is constant, hot or cold.

Any help is much appreciated, and thanks in advance!
 

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well, what i'd do if i had to try to fix it:

look at the plugs for any hints.
compression test.
fuel pressure test.
plug lead terminal depth - are they sitting on the plugs correctly?
tps setting - has it been baselined?
throttle balance.
idle mixture - good/clean/dirty?
rotation sensor resistance cold and hot and gap.

somewhere in there it should show up.

don't think i've ever seen a bad 4v coil.
 

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Voltage regulator overheating? its been a while but I had similar issue when I got my 996 years ago, but it stopped completely when I relocated the voltage regulator to the tail section area. Problem I had was the regulator was overheating and thus not regulating voltage and thus creating voltage spikes or lows at idle and the idling issue because the sparks would not be strong enough at idle to sustain continuous idle. Obviously, it was working fine in cold temps, but hot temps was creating the overheating. relocating to a cooler area of the tail section solved my problem, I would look into that and even if this is not it, the voltage regulator is a known possible issue area and would be a good thing to relocated anyways cause in the fairing side where it is gets pretty toasty in hot temperatures and is not really great for the regulator either anyways.

just my bits
 

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Discussion Starter · #4 ·
well, what i'd do if i had to try to fix it:

look at the plugs for any hints.
compression test.
fuel pressure test.
plug lead terminal depth - are they sitting on the plugs correctly?
tps setting - has it been baselined?
throttle balance.
idle mixture - good/clean/dirty?
rotation sensor resistance cold and hot and gap.

somewhere in there it should show up.

don't think i've ever seen a bad 4v coil.
Good info, thanks. Plugs looked decent, but did have some black carbon on them. I changed out to Irridiums. Still an issue.
I wouldn't imagine it would be compression, as the bike does actually idle okay, on rare occasion. Terminals are sitting on the plugs secure, and the boots appear to to be free of damage.


Voltage regulator overheating? its been a while but I had similar issue when I got my 996 years ago, but it stopped completely when I relocated the voltage regulator to the tail section area. Problem I had was the regulator was overheating and thus not regulating voltage and thus creating voltage spikes or lows at idle and the idling issue because the sparks would not be strong enough at idle to sustain continuous idle. Obviously, it was working fine in cold temps, but hot temps was creating the overheating. relocating to a cooler area of the tail section solved my problem, I would look into that and even if this is not it, the voltage regulator is a known possible issue area and would be a good thing to relocated anyways cause in the fairing side where it is gets pretty toasty in hot temperatures and is not really great for the regulator either anyways.

just my bits
? Interesting. I can see this happening. I will definitely research how to check the voltage regulator, too. Thanks!
 

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Discussion Starter · #5 ·
http://www.triumphrat.net/speed-tri...ier-regulator-upgrade.html#/topics/104504Well,

I let the bike cool a little (still warm, though), then checked the voltage at the battery.

Condition 1 (key off): 12.56vdc. Should be 12.X vdc range.
Check.

Condition 2 (key on, motorcycle off): 12.09vdc. Should be 12.X vdc range, with a slow loss.
Check.

Condition 3 (key on, motorcycle running): should be in the 13.X vdc range.
Negative. I am still at 12.56-12.6 vdc range.

"Condition 3 is what we are most interested in with respect to charging capability. Voltage should be at least in the 13’s at all engine rpm. You may detect it will fall off slightly as you raise engine rpm. This is not atypical performance."

I am wondering now if this is the issue. It is only a half volt off, but still.
When warm, the bike runs with no sign of a failing battery or charge.
 

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Discussion Starter · #7 ·
Is the idle too slow?
There really is no idle. On rare occasion, it will idle around 1,500 RPM or so, but for the most part, I have to massage the throttle a little, to keep it running. I did try adjusting the idle stop screw, which made another very interesting issue. If I gave it a 1/8th turn, it would idle around 2,500-3,500RPM. If I turned it back 1/8 turn, it wouldn't idle at all. Weird.
 

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Post a video of the issue. One with cranking, a successful start, and idle until it fails. Sound and and a view of the tach.

You have a simple problem, but it one or two of many things.

Regulators typically did not overheat on the older bikes. That doesn't mean that the problem did/does not occur, it's just not common. And, you aren't describing a charging problem. Maybe TPS (throttle position sensor) Maybe fuel connectors not fully seated but staying in place. A video will help us narrow it down.
 

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Discussion Starter · #9 · (Edited)
Post a video of the issue. One with cranking, a successful start, and idle until it fails. Sound and and a view of the tach.

You have a simple problem, but it one or two of many things.

Regulators typically did not overheat on the older bikes. That doesn't mean that the problem did/does not occur, it's just not common. And, you aren't describing a charging problem. Maybe TPS (throttle position sensor) Maybe fuel connectors not fully seated but staying in place. A video will help us narrow it down.
I am certain it isn't a disconnected connector, or not properly seated connector) as this issue occurred with the OEM as well as the new metal fittings (which snapped in with a solid click. I also tugged on the fittings to assure that they were indeed seated). I also had the local auto parts store check the battery (in the motorcycle, he did not remove it), and said that the battery was good. Here is a video of the no-start issue.

https://www.youtube.com/watch?v=pSfhc5DwUhI&app=desktop

Note: After I got in from a 30 minute ride, I put the bike on my front porch, as there was a big storm coming up. I let the bike cool (about an hour or so) before filming this video. The voltage (checked at the battery tender) was 12.09vdc, with the key off. With the key on, it was 11.75vdc. A little low, so I put the Battery Tender on it (charging now.)
I will do another video, showing the idle issue, here in a few. Thanks a lot for all the help!
 

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Discussion Starter · #10 ·
Post a video of the issue. One with cranking, a successful start, and idle until it fails. Sound and and a view of the tach.

You have a simple problem, but it one or two of many things.

Regulators typically did not overheat on the older bikes. That doesn't mean that the problem did/does not occur, it's just not common. And, you aren't describing a charging problem. Maybe TPS (throttle position sensor) Maybe fuel connectors not fully seated but staying in place. A video will help us narrow it down.
Here is another video. The only reason it was running was because I had cracked the throttle slightly. Still died, nonetheless.

https://www.youtube.com/watch?v=YT_lWHfi51s
 

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i forgot "check battery charge voltage". i'd probably do that before i pulled the plugs.

was your running test with it idling or with rpm? to check the charge voltage you need 4,000 rpm or so. it should have 13.5v+.

if you have 12.5v with rpm it has a charging problem. fix that first, but i doubt it's all your issue.

see here: Brad The Bike Boy: Charging system diagnosis procedure
 

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Note: After I got in from a 30 minute ride, I put the bike on my front porch, as there was a big storm coming up. I let the bike cool (about an hour or so) before filming this video. The voltage (checked at the battery tender) was 12.09vdc, with the key off. With the key on, it was 11.75vdc. A little low, so I put the Battery Tender on it (charging now.)
I will do another video, showing the idle issue, here in a few. Thanks a lot for all the help!
12.09v ,, the battery is poor
11.75v ,, I’m guessing your headlights are on all the time ( under load ) ,, the battery is very poor.
If these were taken after a ride, your battery is not being charged
R/R is probably on the way out
 

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I wouldn't imagine it would be compression,
doesn't matter what you wouldn't imagine, or think. you need to know stuff is right. when you don't know what you're doing (you don't), you need to cross every step off as a definite yes or no. that's why you test comp and fuel pressure - then you cross it off the list as not a problem, or you fix the problem you find.

if it has a comp or fuel pressure problem the "i can't imagine it's an issue" mentality means you'll never fix it, no matter how many irrelevant parts you throw at it. it probably doesn't have a comp issue, but it might have a fuel pressure issue.

it could have really loose closing clearances too, but that's hard to diagnose without actually inspecting or checking the o2 and hc in the idle mixture, and i doubt you've got the gear to do that - so it gets harder as it goes along.

but it's a process, and you tick off boxes as you go, or fix the shit you find wrong.

haven't you only just bought this?
 

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Discussion Starter · #15 ·
i forgot "check battery charge voltage". i'd probably do that before i pulled the plugs.

was your running test with it idling or with rpm? to check the charge voltage you need 4,000 rpm or so. it should have 13.5v+.

if you have 12.5v with rpm it has a charging problem. fix that first, but i doubt it's all your issue.

see here: Brad The Bike Boy: Charging system diagnosis procedure
I will look into it... thanks. I don't recall what the RPM was when I checked it, honestly. I'll check it again, tomorrow.


Note: After I got in from a 30 minute ride, I put the bike on my front porch, as there was a big storm coming up. I let the bike cool (about an hour or so) before filming this video. The voltage (checked at the battery tender) was 12.09vdc, with the key off. With the key on, it was 11.75vdc. A little low, so I put the Battery Tender on it (charging now.)
I will do another video, showing the idle issue, here in a few. Thanks a lot for all the help!
12.09v ,, the battery is poor
11.75v ,, I’m guessing your headlights are on all the time ( under load ) ,, the battery is very poor.
If these were taken after a ride, your battery is not being charged
R/R is probably on the way out
The voltage is typically around 12.5-12.75VDC. This was after turning the engine over a few times, so that may be some of the low voltage issue, but I will take it for a ride again tomorrow, and recheck it both before and after.


I wouldn't imagine it would be compression,


doesn't matter what you wouldn't imagine, or think. you need to know stuff is right. when you don't know what you're doing (you don't), you need to cross every step off as a definite yes or no. that's why you test comp and fuel pressure - then you cross it off the list as not a problem, or you fix the problem you find.

if it has a comp or fuel pressure problem the "i can't imagine it's an issue" mentality means you'll never fix it, no matter how many irrelevant parts you throw at it. it probably doesn't have a comp issue, but it might have a fuel pressure issue.

it could have really loose closing clearances too, but that's hard to diagnose without actually inspecting or checking the o2 and hc in the idle mixture, and i doubt you've got the gear to do that - so it gets harder as it goes along.

but it's a process, and you tick off boxes as you go, or fix the shit you find wrong.

haven't you only just bought this?
Oh no, I never said anything about crossing this off without checking it. I was planning on doing a compression test this week. My statement wasn't dismissal, only saying that from my experience dealing with automotive engines, low compression is constant, and therefore making me think that this was not a compression issue. But again, I definitely was going to check the compression, this week, especially since I am going to have to pull the tank again, anyway.

And yes, I bought it a couple of weeks ago. New to me.


I changed out to Irridiums.
I have to ask ,,, Why?
They were recommended replacements.
 

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Maybe this will help... I had a parasitic (small) drain somewhere in the wiring harness. After awhile I just ran the red wire from the RR straight back to the (+) on the battery. Great voltage at the battery ~13.5-13.75 volts when running....
 

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Discussion Starter · #18 ·
Maybe this will help... I had a parasitic (small) drain somewhere in the wiring harness. After awhile I just ran the red wire from the RR straight back to the (+) on the battery. Great voltage at the battery ~13.5-13.75 volts when running....
I will do a voltage drop test when I have a little more time, among other electrical checks. I don't think that is causing my idle issue, since it does it, even with a fresh charge, but I could see something like that contributing to the no-start issue.
Thanks.

They were recommended replacements.
Recommended by who? The person selling them?

What benefits are there to be gained by using iridium plugs?
Internet forums from other Ducati owners, as well as tech support with NGK. Why, is there a problem with running Iridiums? I am not really concerned with the money, they were $8.99 each. These came highly recommended.
 

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Discussion Starter · #19 · (Edited)
I just went out to start it this morning, after it sat on a trickle charger all night. Unfortunately, I didn't have an actual battery charger, but will take it to the auto parts store to have it charged in the next day or two. Here are the readings.

*Immediately after unplugging the Battery Tender: 12.96vdc

*After a couple of very short cranks: 12.53vdc

*Key on, engine off: 12.20vdc.

*Engine running at 3,500RPM: 13.20vdc.

Attached, is a picture of the plugs that I pulled out, a week ago. I marked them "V" and "H" for vertical and horizontal cylinders, for later diagnosis. The plugs do not appear to be physically damaged (electrode, insulator, etc.), but do have a light (not coked on) coat of carbon on them. The motorcycle had slightly over 9,000 miles on it when I pulled them, and think they are the original plugs, but not 100% sure.
15299359735471085286752_1529936012214.jpg


And here is the follow up video of the no idle scenario.

https://www.youtube.com/watch?v=Ezzo89Mu_qQ
 
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