Ducati.ms - The Ultimate Ducati Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
134 Posts
Discussion Starter #1
Okay, here's the mystery.
1.Vertical cylinder has good spark and fuel.
2. Horizontal cylinder has good spark and fuel.
BUT, when I start the bike up, only the vertical cylinder works. the horizontal
head stays cold. SO, i remove the HT wire to the vertical cylinder and start
her up again...Horizontal cylinder works fine ! I kill the motor and re-attach
the HT wire on the vertical head and start her up again...Horizontal cylinder
does not fire up. any thoughts ?
 

·
Registered
Joined
·
1,910 Posts
Help us help you. What are we talking about, year and model?

Secondly, what wire are you switching? Re-read your post, it's very confusing.
 

·
Registered
Joined
·
134 Posts
Discussion Starter #3
No switching involved. read it again, it's very linear... but here goes...
1992 carbie.
1. I checked both cyclinders for spark and fuel. both were good.
2. I start her up... the horizontal head does not fire. vertical head works.
3. I kill the engine.
4. I remove the sparkplug wire to the vertical head. I start the engine....
horizontal head works fine. I then kill the engine.
5. I then put the vertical sparkplug wire back, i start the engine....
Vertical head runs fine... horizontal head does not fire.

That's the problem i have with the bike.
 

·
Registered
Joined
·
313 Posts
A weak or defective plug wire or boot? How have you checked spark? Try progressively increasing the gap until it doesn't fire and see if you can tell if the spark is jumping somewhere else. Compare that to the other cylinder, there should be a difference in at least the distance the spark will jump between the two coils. It might be easier to see the spark jumping elsewhere if you perform the test in the dark.
 

·
Registered
Joined
·
1,910 Posts
Here's how I interpert this:
With both plug wires attached to the plugs only one cylinder runs, the vertical.
Disconnect the vert. plug wire from the plug, and the horiz. cylinder will runs.
Put the vertical cylinder wire back on and it only runs on the vertical cylinder.

Correct? Not tyring to be a dick, just trying to understand.

Sounds like a power problem. There is enough power to energize one coil, but not both. Check the wires going to each coil and the coil surfaces where it attaches to the frame. Check the coils for cracks. Check the engine ground to frame/negative terminal also. Lastly, pull the boot back and check the multi pin connector to the "ecu". Is there some slack in the wiring or is it tight enough to pull on the plug connection? (My Paso would intermittently drop one cylinder, the multi-pin plug wiring was just tight enough to disconnect the last pin.)

If all else fails, wait till it's dark, start the engine and check for small electrical arcs. A small amount of water, from a spray bottle, around the plug wires & coils may help isolate the cause.

Let us know what you find.
 

·
Registered
Joined
·
134 Posts
Discussion Starter #6
Ducati Austin checked my coils. they said they were good. I will look at all the connections again and see what I find. thanks all....
 

·
Registered
Joined
·
998 Posts
Check the clips on the leads going to the coils. Pinch the clamps together a bit for a positive connection, especially on the horziontal cyl. coil. Make some slack in the wires around the battery box.
 

·
Registered
Joined
·
48 Posts
DD........question. By any chance do you have a timing light? I'd first be insterested to know (with all connected as they should be), if you first connect to the vertical, does the light trigger. (And according to what you say this is the one that works, so it should).

Then, connect it to the other, while the engine is running. I'd like to see if the "spark" is traveling to the plug itself first.

...the thought here just being to take the ignition as far into/onto the cylinder as possible.
 

·
Registered
Joined
·
1,274 Posts
I've seen this before.I could be a dick and stop right here. But I won't. Pull the leads that come from the ign. pickups and check the resistance.They should be around 220 ohms per cyl. Now check one lead from one pickup to the leads from the other pickup. You should have an open circuit. Do the same with the other lead.What you are checking for is shorting wires between the pickups.Anything but an open circuit indicates a breakdown in the insulation in the wires between the pickups and the terminals.This usually occurs at the grommet where the leads pass through the left side cover but can also happen if the wires have been pinched or mashed anywhere.Hope this helps. Bill
 

·
Registered
Joined
·
859 Posts
If you have a multi meter check the resistence in the leads to the ignitor boxes, refer to your manual for the actual readings. I had a similar problem a couple of years ago and found a break in the wire from the pickups on the fly wheel. I had to remove the left side engine cover and replace the sub harness. The really strange thing was the external plastic coating on the wire wasn't broken but I could feel the break inside. Old wiring gets brittle and Ducati use cheap light gauge wire. The next electrical failure you might run across could be the wires to the fuel pump, wires to the starter solenoid plug, ingition switch,regulator. ... it all fails eventually. I know I have fixed all this shit on my bike.. always seems to fail half way through a track day
 
1 - 10 of 10 Posts
Top