Ignition trouble when hot?

[JBMatthews82]

81 XS650. I’ve had nothing but issue after issue as far as electrical system goes since completing this build. What’s on the bike as of right now. Mikes XS red ignition. Hughs charging system. 4 cell anti gravity battery. Ignition coil is from Mikes XS. Part SI-165-2. 2.4 ohm. Mounted in factory location. I do have a high tunnel tank so there’s very little room above the engine but it all fits. All of this is less than a year old. I tried running a capacitor for a while and decided to just eliminate that by installing the 4 cell antigravity battery in its place. The current issue is when the bike gets hot in traffic, town or parking lot cruising low speeds it starts busting out and skipping. More so at lower rpm’s. If I can get it back out on the open road it’ll go back to normal after a few miles. Everything on the bike has been changed recently except for the coil. It’s still only about 16 months old. But could it be causing this issue I’m experiencing? Seems like something is getting hot at low speeds or idling in traffic. Is the location being buried under the tank causing it to malfunction?

 

[Jan_P]

If I get this right it runs well at low rpm Cold but not Hot
A Voltmeter installed on the bike would help I Would suspect the charging first
But difficult at this point to guess.

 

[JOHNDADDY]

Sorry to hear of your grief. I have the same problem with my 75. I'm in the boonies though so I don't have to deal with much traffic unless I go to an event or such. Good luck with it, I'm sure the folks here can help. Maybe me too. Nice looking bike!

 

[gggGary]

Everything on the bike has been changed recently except for the coil.

Coils breaking down electrically at high temps is a thing.
Some of the MikesXS coils have long had a less than stellar reputation. Subbing in a known good coil seems an easy and likely way forward.
I'm very fond of Accel 140403 coils but there are many high quality coils that work well. Also several used coils (there's a Honda part number many have used.) that seem to reliably spark forever.

 

[JBMatthews82]

Coils breaking down electrically at high temps is a thing.
Some of the MikesXS coils have long had a less than stellar reputation. Subbing in a know good coil seems an easy and likely way forward.
I'm very fond of Accel 140403 coils but there are many high quality coils that work well. Also several used coils (there's a Honda part number many have used.) that seem to reliably spark forever.
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When it comes to coils don’t they have to be matched to your ignition system in terms of ohms? So the mikes xs red ignition came with a 2.45 ohm coil but it wouldn’t fit under the tank so I purchased one from them that would fit under the tank and it’s 2.4 ohms. So am I stuck using something in this range or how far can it vary?

 

[gggGary]

You can go a bit higher but no lower, anything in the 3.0 ohm range should be fine.

 

[5twins]

The used coil many of us use is the Honda MP08. It's very reliable and can be found quite cheap on eBay. It has a 3 ohm primary resistance. Details are here .....

https://www.xs650.com/threads/honda-mp08-coil.55408/

 

[JBMatthews82]

Thanks for the information. I was able to purchase 3 of those MP08 coils from a gold wing for $40. Arrived today. Making a little sheet metal piece to allow it to bolt up in the factory location. I’ll test it out this weekend hopefully. Replacing the clutch next! Not noticeable all the time but she slips at higher speeds and it can be hard to find neutral when I park after a long ride.