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Buell Motorcycle Forum » Quick Board Archives » Archive 0212 (December 2002) » Technical » Duelplug heads « Previous Next »

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Keith
Posted on Thursday, December 12, 2002 - 06:43 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I have a 98S sportster and am installing thunderstorm heads and pistons.I don't want change my ignition I would rather use the duel plug set up but a H-D mechanic at a H-D dealership suggested thatI just ground one side of the coil to the frame and run with one plug and save my money on the machine work to have the heads tapped for the second spark plug.This doesn't sound right to me anyone have any real idea if this would work or would destroy my coils and create other probems as well...
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Aaron
Posted on Thursday, December 12, 2002 - 07:26 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Keith: the "S" coil is a pair of dual-output coils in one package. One of the dual-output coils feeds the front cyl, the other feeds the rear cyl.

Every dual-output Harley & aftermarket coil I've ever put the ohmmeter on had the spark plug terminals wired at opposite ends of the secondary coil. What this means is that the spark plugs are wired in series. Current flows out of one secondary terminal, through the spark plug, through the cylinder head, through the other spark plug, and back to the other coil terminal. The secondary is not referenced to ground.

So, to use a dual-output coil like this and yet use only one output, yes, you need to ground the other output. Otherwise you don't have a complete circuit. Oh, it'll fire anyway, because the coil isolation is far from 100% and there's coupling back to the primary which is close to ground. But the voltage will be weak and your ignition module might not last long.

He's steering you right ... although personally, I'd probably either change to a nice two output single fire coil or dual plug the heads, just to do it cleanly.
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Jadow
Posted on Friday, December 13, 2002 - 08:23 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Why not modify your stock dual plug heads to fit the T-storm pistons. I would modify lightning heads to fit the dome pistons and use them in the sport twin series. you get a great controled squish area and the combustion area gives you a clean burn. Nallin could probably modify your heads and flow them to better a stock set of T-heads! Use what you got...the only problem would be the limited ignition modification available.
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Newfie_Buell
Posted on Friday, December 13, 2002 - 08:35 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Just change the coil, if your spending the bucks on the heads then complete the job. Grounding out the dual plug coil just does not seem right.

If cost is a factor for new I am sure someone in the classifieds section of this board may have one to sell or try the ever popular e-bay. There has got to be a bunch of those things around.
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Jssport
Posted on Friday, December 13, 2002 - 11:29 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

You have a 98 XL1200s model ??


Please reference the previous Quick Board topic which completely covered this subject.

Thenderstorm heads / Dual plugs
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Jssport
Posted on Friday, December 13, 2002 - 11:30 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

On the the 1200s you can't "just change the coil"
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Richieg150
Posted on Saturday, December 21, 2002 - 10:42 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

My suggestions for the 98S Sporster are-1)Take it to the car wash and get it really clean,2)take it back home and park it in the drive,3)go in the house and get some hot dogs and a stick,4)go back outside and liberally douce the bike with gasoline,5)throw a match on the bike,6)while it is burning you can now cook your hot dogs!If you want a bike that runs like a BUELL,get a BUELL!
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Richieg150
Posted on Monday, December 23, 2002 - 06:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

:)HE HE
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Cyclone1
Posted on Monday, December 23, 2002 - 08:21 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Richie, Richie, Richie...where's the brotherly love, man?? ;) heehee

Frank
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Richieg150
Posted on Tuesday, December 24, 2002 - 08:41 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I wuv him Frank really I do!
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