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Discussion Starter · #1 ·
Figured Id post here instead of my build thread since it really isn't build related.



As the title states I have an off-idle miss/drop in RPMs that I can't seem to figure out. Here is a video that I was able to catch today showing the tach at the time of the drop:



http://www.youtube.com/watch?v=JE2jZX8-kTc&feature=youtube_gdata_player



Background on the bike: New cam chain/mech seal, ignitech, pod filters, 2-1 exhaust, 90/120 jets, brass rods in plug caps (same result before and after), mixture screws 3 turns out (I have tried 3 1/2, but get same results). Plugs look ok, but I'm gonna swap them for new tomorrow.



Let's hear what everyone thinks, and get this sorted.



*EDIT* - Forgot to mention I have cleaned the carbs.



Idle circuit? ACVs?
 

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Just a few guesses,



Maybe a sticky float,,check to see it the floats are able to move freely. If one of the floats was hanging for a bit before dropping and letting more fuel into the bowl it might cause a short period of fuel starvation. Using clear tubing on the drain/overflow held up beside the bowl as a sight tube might show if this was happening.



Float adjustment,,check to see if the floats are set correctly.



Check the float needles to see if the pins in the ends are seized up.



Hairline crack in a plug boot.



Loose connection somewhere in the coils/ignitech wiring.



How often does it happen? If it happens frequently you could try running it with a plug wire unplugged. If it does not happen then try plugging that wire back on and unplug the other side and running it,,It may quit when it happens,,this would point to the side to concentrate on.

A timing light would work to see which side the problem was on too,,if the problem is electrical.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Bad coil. Was the first electrical gremlin that I wrestled with on the Grub. I think it was David in Wisconsin who gave the the answer.



Also, you may be a little rich. The specified initial setting on the '78 is two turns out, and goes down to 1-3/4 turns on '80 and later. (But I've never noticed changing the idle mixture to have any affect on rpm.)





R
 

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I would agree that it seems to be an electrical issue. It is like one side drops out all at once.
 

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Discussion Starter · #12 ·
Thanks guys, I am aware of these replacement coils, but was looking for coils with detachable HT wire, I can't find them anywhere and don't feel like dropping $150 on dynacoil or accel super coils. I think I'll pick the cheap o's up and see if that helps. I'll jump back to this post after I replace them and let ya know how it turns out.
 

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In the link I posted,,Randall mentions that one of those sets of coils has removable HT leads. Don't know if he tried them or not.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Thanks guys, I am aware of these replacement coils, but was looking for coils with detachable HT wire, I can't find them anywhere and don't feel like dropping $150 on dynacoil or accel super coils. I think I'll pick the cheap o's up and see if that helps. I'll jump back to this post after I replace them and let ya know how it turns out.
I looked for them on eBay, and I think I even asked the vendor that I got the cheap one from, but I never found an applicable coil with a removable cable. I've never seen a Dynacoil or Accel that would work with the 80 deg V-twin, either.





R
 

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Discussion Starter · #15 ·
I looked for them on eBay, and I think I even asked the vendor that I got the cheap one from, but I never found an applicable coil with a removable cable. I've never seen a Dynacoil or Accel that would work with the 80 deg V-twin, either.





R


A few vendors claim they have the dyna coils (Z1) and accel super coils for our bikes, but I didn't investigate too hard because of the high cost.
 

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I've always been surprised at the speed stuff comes to me from Hong Kong. Maybe a week tops.
 
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