High altitude issues.

[trbig]

Coil problems happen in pairs, not a single cylinder.

[motoman]

Coil related, if the later 3ohm Yammy coils check out 'marginal', and your a cheap-azz like me, locally bet you could come across a set of Honda VF series coils. For whatever reason Honda coils rarely go 'south'. Take your meter with ya' and check across both poles for 3ohm. Alot of the VF series coils were 1.5ohm and some 5ohm. I picked up aset locally for $20, went to NAPA got 5ft. of high-temp 7mm multi- steel wire and cut to length. Check that a used set of VF coils has the screw-on caps AND inner rubber sealing washers. Those can be got new from Honda if necessary. 8mm wire would of been my preferance.....just cause, but pretty sure that would have split the screw-on caps, which push the rubber seals against the coil side inverted flare for a water tight seal. If you get ham-fisted tightening the caps/ seals, the cap WILL split....DAHIK.
BTW, the VF coils throw a 'hot' enough spark, that you'll NEVER 'drop' a cyl. due to richness unless you just pour the fuel in the cylinders.....and they ARE plug'n'play. If you end up going that route, same thing, unsolder your OEM wire plug-ins and re-solder to the VF coils.
Interesting as to which gremlin you find is the culprit..... igniton related, fueling related, or a bit of both. Hearing your bike running on occassion even tho behind me a couple bikes, my bet is a bit of both. Just didn't have that crisp, smooth sound out the exhaust.

[BA80]

Pulled the timing cover today, the breaker plate was stuck in the full retard position. That should not have caused the issue though since on WOT that's where it goes anyway.

[3Phase]

Pulled the timing cover today, the breaker plate was stuck in the full retard position. That should not have caused the issue though since on WOT that's where it goes anyway.

I've left the vacuum advance disconnected/full retard and it ran like a goldfish on Benadryl but the engine didn't misfire or stutter.

I don't about know about no vacuum advance at all at WOT on a normal engine though. It might drop back and retard at low speed when you pop open the throttle but the manifold should start to pull at least 2 inches of vacuum when the RPMs get rolling and the advance pot's all-in at only 6 inches.

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[jwhughes3]

NEVER go full retard

John

[3Phase]

NEVER go full retard

John

Yeah, it's not really 'tarded, it's just stuck at baseline zero with no additional advance. Unless the '81s or XJs have a ignition Start retard circuit in their TCIs, none of the ignitions in these bikes retard anything.

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[TopCatGr58]

Coil problems happen in pairs, not a single cylinder.

Hey Tod,

Usually that's right, but like IIRC TadRacer said, and I've seen it reported as well, when the voltage gets a bit LOW on one coil for any reason, the power of the spark drops...so that it can go thru the primary plug...but doesn't have enough power to then go thru the engine and back up the other plug on the paired coil....so a person gets 1 clyinder dropping out due to electrical problem....too low voltage to the coil.

T.C.

[BA80]

Yeah, my last set of coils just one cylinder died. I think one wire went bad.

[motoman]

+1 to T.C.'s last four words!......and if it goes on for too long.....slow death to the coils.

[BA80]

The ballast resistor sort of guarantees low voltage doesn't it Brant?

[motoman]

The ballast resistor sort of guarantees low voltage doesn't it Brant?

Realative to the 1.5ohm coils it would. If initial pri. ignition voltage is low to begin with, then secondary coil votage is diminised even more, which leads to a 'weaker' plug spark, that plays favoring path of least resistance, leaving the other plug not having nearly as much fun makng explosions........I presume you were still runnin' the stock coils?

[Bonz]

Guys, the issue in my estimation is the larger mains and larger pilots. One size up in pilots is huge from a relative fuel perspective and effectively he is up two sizes in mains from optimal because one size lower mains is typical and legit at elevations the boys were runnng at. Even when pilot screws are adjusted for correct idle with larger pilots, they still will draw more fuel than stock when all the small holes around the butterfly are exposed at higher throttle.

Thicker air will burn that richer mixture, but a constantly higher fuel input from the larger pilots along with larger mains at high elevation (when you technically could run a size smaller than stock like I do on the 80SG) has you pig rich. The dark plug is coincidental from whatever oil control issue that cylinder is having.

I catch a lot of crap and good natured ribbing from guys about the 80SG running 107.5 mains, and perfect plug color even at the top of Pikes Peak at 14,110' elevation (right, 3Phase, motoman and CZ?) , but it is because that is what works for good tuning at higher elevation.

[3Phase]

Yep, Howard, I didn't know Greg had supersized the mains and pilots but there's still something double-plus-ungood going on because that #4 plug was whiter than bone white and that's lean, not rich.


Pike's Peak was a blast! Colorado still owes me for all the 'skeeter fogging I did from the campground to the 'Peak and back too.

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[jetmechmarty]

White porcelain is perfect! That is, until it collects little flecks of aluminum. That's why I look for slightly rich or tan, just like most of the rest of you. Not seeing those flecks, that #4 plug looks about perfect.

[3Phase]

White porcelain is perfect! That is, until it collects little flecks of aluminum. That's why I look for slightly rich or tan, just like most of the rest of you. Not seeing those flecks, that #4 plug looks about perfect.

Exactly.

But he's running the stock airbox; don't remember if he's got stock exhaust or aftermarket. With the jetting he's running it should be rich but the plugs are lean clean.

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