Running on 2 cylinders after bike gets hot

Hey Guys - I know this has been covered, but I am new. And could use a little help, because I am pretty sure I had a bunch of problems and I am finding them all at once.

In a previous thread i talked about fuel delivery in how I had no fuel filter or working screen. I remedied that, currently running a brand new petcock with screen. But - I think I was too late, and a bunch of crap got into my carbs are really messed them up. What was happening was the bike could no longer hold an idle, especially after it is warmed up. A buddy of mine owns a shop here in town, and I took my bike to him. He checked my wires, said spark is getting to all 4... so I paid him to ultrasonic bath my carbs, and resync them. He gave the bike back to me, said he ran it for 20 minutes and it idles up great now and runs on all 4 cylinders.

Today I took it out---- ran it up the highway really to get it up to 5th gear, for about 15 miles... and once I got off the highway.... the bike started to lose idle and die. Same problem!!

I made it to a parking lot, and let it sit for about 10-15minutes. Once all the headers were cool, I fired it up and did a quick touch test on my pipes to discover the same two cylinders, 2/3 were cool to the touch. I called my girlfriend to come get me, and by the time she got there--- about 45minutes later.... I figured I would fire the bike up again and see what it does. And there we go--- all 4 running and idling normally.... I had her follow me and I came back home via the highway. Got home and this time it did not die.... just idling...

One would have to deduce that one of my ignition coil's are dying? I was going to swap the two coils and see if I get the reverse failure in cylinders.... But with it running right --- figured I would come here and ask you guys if you think I am missing anything?

Swapping coils as a test is a good idea. It's possible that the coil that currently fires plugs 2&3 fails when it gets hot. So if swapping coils moves the problem to cylinders 1&4 I think you have identified the problem. Ed

A coil going bad will do what you describe. I think the most common ways to determine if it is indeed a coil are,

Do as you suggest and swap the coils you have. If the other cylinders fail, you have probably solved the problem.

Replace the suspect coil with one known to be good. If it does not act up, smIle and ride on.

Remove the fuel tank and use a heat gun to artificially replicate the conditions you suspect are causing failure. Once hot, use your multimeter to see if the coil fails when hot. Be careful not to melt any wires or connectors.

I suppose you could also throw tools and multimeter in a bag, tie it to the passenger seat, ride until the bike acts up, quickly pull to the side of the road and disassemble the bike to test the coil. Hopefully, you will also have a plan to avoid getting smashed flat by some errant cager. :silly:

yes agreed above, see my recent 'engine rattling' reply regarding failing coils.

Sometimes a multimeter won't show a fault just by reading the primary and secondary resistance values. Just like a domestic electrician will test insulation with a 'megger' and won't pay any attention to resistance values. Sometimes electrical components need stress testing, something an ohmeter won't do.

Classic symptoms of a bad coil. Learned it the hard way.

Grnole wrote: ... the bike could no longer hold an idle, especially after it is warmed up....

Insufficient valve clearances can result in these symptoms.

Cool engine starts and runs okay until it warms up and then runs less okay and won't idle.

Good Fortune!

Thank you everyone. For the cost of replacement coils it's worth it to me to just replace them both. No need to do this twice.

Though Patton--- I do think I have an issue with valve clearances as there is an annoying tap coming from the top end over by cyl 1. It sounds like an exhaust leak, but there is no puff signs coming from the header. I need to measure my valve shims--- but I wanted to wait until the off season before this hopefully it's corrected with the coil swap.

The way I found my valves were leaking was doing a leak down test with some windex.. Take all the plugs out connect a compression tester hose to the spark plug hole and take the right cover off that hold the advancer connect compressor turn pressure up to 30 psi and crank the engine with wrench slowly to see if the valves ever fully close and no bubbles from the windex takes 45 min at max.. Before ripping valve cover off cause belive me so easy to rip valve cover gasket....

Just wanted to post an update to this thread. I seem to have fixed the problem. My bike seems to be a mid-year bike, and there are alot of things I find not consistent with other LTDs. I had the stock electronic ignition system with a factory mechanical advancer. It seems that the stock setup had a resistor, but somewhere along the way that was bypassed, and I had some Emgo coils (1 of which was failing) The way I saw it was - option 1 - Dyna S and dyna 3ohm coils, or option 2- replace everything with a dyna 2000 system including 2.2ohm coils.

I went with option 2. The dyna 2000. What a kick as$ system!!! Out of the box it comes with almost everything you need. All I needed to purchase was new plugs and wire's and my entire ignition system is updated, in a pretty seemless bolt on upgrade.

The timing process was pretty simple. I followed the directions and set up 2/3, and then 1/4. The d2000 also comes with a multitude of other options including curve settings, rev limiter and retard cut-off. At this time, I am not setting my bike up for anything like that... but nice to know I have it if I want it.

Being that my bike is 10:25:1 I went with curve 4. It fires up, Idles right, and sounds great on the highway. The lean pops I was getting have calmed down, and i no longer seem to lose power after a long ride.

Fingers crossed I can get through the season trouble free, and post a "valve shim replacement" thread in the offseason! :ohmy: :dry:

In the meantime thanks everyone!