ign. coil relocation

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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blaster

ign. coil relocation

Post by blaster »

Has anybody out there relocated their ign. coils. The coils get coated with dirt and road grime when it rains or snows. I have to keep cleaning the rust and corrosion off the mounting points which isn't too good for the ground. It looks easy enough,I just was wondering if anybody has a cool trick. Blaster
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ducinthebay
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Re: ign. coil relocation

Post by ducinthebay »

My cool trick to keeping the bike clean is to not ride in the rain and especially the snow.
That's when I retreat to my cage vehicles.

the coils need good air flow, as they will get hot, and excessive heat will kill them. You could, I suppose, put a deflector plate in front of them that blocks the water and debris from the wheel while allowing cooling air to pass over them.

Cheers,
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
blaster

Re: ign. coil relocation

Post by blaster »

thanks for the responce but i don't like cars much so i ride as much as i can and living in the chicago area that means riding in lousy conditions both weather and road. the roads are so bad here i have had to repair the front fairing bracket and straighten both wheels multiple times. when exposed to bad weather for long periods of time the coils develop a few problems, one of which is rusted mounts. this causes to much resistance and the flat male connectors for the primary windings get so hot that the plastic surrounding them gets soft and they droop. a good cleaning stops this but i want to cure the problem. i was thinking of relocating the battery to the lower right side of the motor like my 916 using a 916 battery box. then i could mount the coils and maybe other electrical items in the old battery space. the secondary plug cables look long enough and the airflow to the rear cylinder should improve. most coils that i have seen in sportbikes are mounted in covered up spaces that get pretty hot so i think there shouldn't be a problem. just wondered if someone out there tried something like that. blaster
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ducinthebay
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Joined: Sat Sep 03, 2005 12:00 am
model: 750 Sport
year: 1990
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Re: ign. coil relocation

Post by ducinthebay »

If I were going to attempt this, I would put them on either side of the voltage requlator, just in front of the battery. It will be a tight fit, but might work. I would then put a deflector plate below it to keep the spray from the front wheel. The ST has such a deflector plate. Then I would go through all of your connectors and give them a good cleaning, and a liberal dose of silicone dielectric grease. It helps keep the weather out, and connectors working well.

While you are at it, I highly recomend some new coils. the high tension leads are not replaceable on the stock coils and are a common source of failure of the ignition system. The Dyna Coils are the common upgrade, although not cheap. ($200) Ca cycle works has a nice kit with some nice wires already attached. http://www.ca-cycleworks.com/ I put them on my bike for a noticable improvement. Stock coils are 4 ohm, which is almost impossible to find. After market are generally 3 ohm. You could also find some stock Ducati coils for cheap on e-bay, and they are much smaller.

Cheers,
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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higgy
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Re: ign. coil relocation

Post by higgy »

Bevel Heaven has 3 ohm and 5ohm dyna coils for not too bad of a price. I have on occasion seen the 3 ohm on ebay for cheap.Never seen the 5 ohm anywhere other than BH
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie
blaster

Re: ign. coil relocation

Post by blaster »

has either one of you replaced the stock coils with aftermarket units and still use the digiplex. the service tech from ducati usa told us not to mess with the resistance of the coils or the plugs because it will blow up the ign. unit which i have witnessed. if so, which ones did you use. in regards to the high tension leads a cheap fix which worked well for me was just clean off the cables then slip on some good quality shrink tube and heat. the idle rose slightly and low speed running was noticably smoother and it comes in colors too. please let me know about the coils though i still am a little worried about wrecking my digiplex. thanks blaster
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higgy
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Re: ign. coil relocation

Post by higgy »

I have the 3ohm dyna coils and wires and have had no issues what so ever.
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie
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ducinthebay
paso grand pooh-bah
Posts: 1323
Joined: Sat Sep 03, 2005 12:00 am
model: 750 Sport
year: 1990
Location: SF Bay Area

Re: ign. coil relocation

Post by ducinthebay »

I got a set of high output aftermarket coils from a friend, and the company doesn't even make them anymore. They were originally for a HD, but they were 3 ohms. Just to be safe, for the exact same reason you gave, I added a big ol' 1 watt 1 ohm resistor in line. I talked to several EEs. and none could agree whether a 3 ohm coil in a system that had a 4 ohm coil before would be bad, or not. I had three engineers hotly debating it, but since they couldn't agree on what the architecture of the Magnet Marelli box might be be, they couldn't speculate as to what the affect would be. To be safe, I just added a resistor.

Others have said it won't matter at all. when I made the change, I e'mailed every company rep I could find. Most did not return my requests, and the few that did, said it didn't matter. None of them were terribly convincing.

Cheers,
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
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jcslocum
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Re: ign. coil relocation

Post by jcslocum »

Electrically I'm a dunce. What is the difference between a 3ohm coil and a 4 ohm coil?
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higgy
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Re: ign. coil relocation

Post by higgy »

1 ohm :lol:
diodes require regulated voltages to keep them from being destroyed by excessive reverse bias,heat is the enemy
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie
User avatar
ducinthebay
paso grand pooh-bah
Posts: 1323
Joined: Sat Sep 03, 2005 12:00 am
model: 750 Sport
year: 1990
Location: SF Bay Area

Re: ign. coil relocation

Post by ducinthebay »

silly answer; 1 Ohm.

technical answer; the coil is part of the circuit that is a capcitor/resistor trigger. If the resistance is too high, or too low, the proper amount of voltage that goes into the computer is changed. Depending on how sophisticated the circuitry, it might or might not change its behavior. Since the coil works on a field collapse, the computer is running the current that goes through the coil to ground to excite the field. Then it opens that circuit, and the field in the coil collapses and sends a massive spark. And that's where my knowledge ends. Remember points and the pitting of them? Well, you computer is now doing that job and relies on the resistance in the coil to balance the system and create sparks in the spark plug, and not in your computer.

Cheers,
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.
blaster

Re: ign. coil relocation

Post by blaster »

this is interesting, i only know the basics too but having had to come across with either $300.00 or $600.00 (its too painful to remember) because i tried nonresistor plugs i'm a little nervous. i also destroyed the ign unit in one of my racebikes when i installed a set of aftermarket coils and found out the hard way that the supplier set me the wrong resistance coils. the difference was only something like 1 ohm versus 3 ohm but thats all it took. is there a pattern here? oh, i think i saw a 5 ohm dyna coil in the dennis kirk cataloge. well thanks for all the help, i might take the plunge with new coils and if i smell burning olive oil with a hint of garlic there is a guy on ebay in tennessee or kentucky who claims he can repair the digiplex or i can switch to the kokusan. blaster
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higgy
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Re: ign. coil relocation

Post by higgy »

In ignition circuits, a higher resistance coil is"safer" than a lower resistance coil. My understanding is with the digiplex either the 3 ohm rated or the 5 ohm rated are OK.
I am currently using the 3 ohm dynacoils with no problems with the digiplex.
And here is the guy who can fix them with a lifetime warrenty as well.
http://cgi.ebay.com/ebaymotors/ws/eBayI ... &viewitem=
Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie
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