Sudden loss aof spark

[machinest]

1980 550L
I was riding back from work today and about halfway home the bike loses power doing 55 and all of a sudden the bike will only do about 40 with full throttle . limp the bike home and start to check things ,pipes from cylinders 1&4 are cool (right hand coil ), pull seat and tank off and check wiring all seems good mess with bike for a wile and get some life but at end only two cylinders firing . tomorrow after work will check all wiring between ignition and coil . My question is can a coil fail all of a sudden and is there a way to check for a bad coil.

work done on bike
Carbs pulled dipped and O rings replaced
Coil relay mod
Valve clearance done
carbs synced
all electrical connectors cleaned or upgraded
petcock replaced
RR replaced and rewired (PO mod)

[hikermikem]

I think a coil could indeed just up & fail, especially if heat is involved. You can check the coil with an ohmn meter with the key off, should read about 30-50K on the primary side, and about 5 on the secondary (as I remember, could have that backwards).

Check the plug caps - they are known for corrosion issues resulting in limited/no spark.

A good upgrade is the dyna-coils, looking at about $125 from Z1.

good luck.

[lucabond]

Since you did the coil relay mod do you have +12 at the suspect coil ? Pull a plug from that coil with the plug wire connected and ground it, then with the +12 on 1 side of the coil pull the other wire and connect a jumper wire to it, ground and unground the jumper doing this the plug should spark . No spark and the coil or plug wire are bad.

[machinest]

Played with the coils some and replaced one bad coil but no improvement or rather temporary improvement bike ran OK until it warmed up then two cylinders cut out (1&4) got it home and no spark to those two plugs swapped the coils over (input & output) and the same situation occurred so its not the coils .Can half the igniter box fail or is it a all or nothing type thing . also may try replacing the connector between the pickups on the end of the crank and the harness proper as it is one of the few connectors I only cleaned as I would have to splice in extra wire to get it to fit,

[SqDancerLynn1]

Time for a Dyna Ign. The ignitor is probably failing when it get hot

[machinest]

This may sound like a silly question but is the Dyna S a complete stand alone unit or dose it use the cdi box on the bike.

[hikermikem]

It replaces the ignitor. I believe there are two types of Dyna ignitions - one to replace the OEM Nippon Denso (ND) points plate & one for the other OEM points plate (KD).

Pull the points cover off & look for the marking (NP or KD) on the plate. Then call Z1 & buy the appropiate one. Rob at Z1 will walk you through the process.

http://www.z1enterprises.com/catalog.aspx?pid=MFDY2

Good luck