I am usually in the Shovelhead section, but have an issue with my wife's 2005 XL1200R.

After sitting for about a week with "50 miles old gas" I started it on Sunday... I was running in 1 cylinder. Playing with the plug wires both cylinders were working, but just not fine. Got new plugs and started it today
a lot better BUT not right at all even after bike warmed up.
Sympthoms:
-erratic idle and at low speeds.
-when at idle if I unplug the rear plugwire id idles nice ON ONE CYLINDER. PAT PAT PAT PAT PAT PAT PAT
-If I put the rear wire back is erratic again: PAT PAT PAT PUM PAT PAT PUM
-If I remove the front wire while idling the bike dies
-I swaped wires R & F and same thing, the rear has issues.

The bike's been running with new mufflers, rejetted CV and Hypercharger air filter for months now and no problems.

Any ideas? I can only think about the coil, but these bikes have too many things on them to my taste

thanks

 

if you take the rpm's up and the miss goes away ,it could be your battery is weak.

 

Get some Fuel Injector Cleaner and dump some in your tank. That should clean up any carb issues with old gas. You have eliminated the plug wires, so that leaves the coil and the Ignition box. Check the resistance with an Ohm meter. I don't have the values, but they are in the Shop Manual. Last step - replace the Ignition Unit.

 

sounds like slow jet is stopped up put a visul filter under the petcok works great you see all the junk that gets past the tank filter. Just clean out the slow jet
http://www.ebay.com/itm/HONDA-TRX-25...b6df9d&vxp=mtr

 

resistance on the wires is slightly above 5 in one and like 5.4 in the other. Manual says between 5 and 11 I think.
Even if I swap the wires I have the same issue... front runs fine, rear does not
Will check the carb... but if it was the carb I'd guess both cylinders would have issues?

 

Does the miss go away when you take the rpms up to 2000 or so.

 

nope... still there
less noticeable, but if I keep the throttel steady at 2-2500rpm I hear it

 

You could try and spray some carb cleaner around you rear intake gasket while at idle and see if you here a difference.

 

Just tried, no difference
Tested the coil: resistance between middle wire (power) and F or R pin is 1.0-1.1 Ohm and between R and F is aboput 1.4-1.6
My understanding is that those coils (single fire OEM) are supposed to be 0.5

Secondary resistance between coil outputs F and R is 12.100, between F output and center prong is 6.000 , between R output on coil and center prong is 6.100. I think these values are about right.

That being said... resultos for F and R are pretty similar... but R cylinder still misfires...

 

One more detail
The coil test was made with the bike cold/slightly warm. Not sure how different the results would be.

another weird think is that the plugs get BLACK and soothed in a couple of miles. Never happened before.
The bike was rejetter before winter, new pipes then and another set of pipes a month ago... the bike was ridden though and was riding fine; while now, even if I clean the plugs or put a new set (just did) rides OK-ish for the first mile, and the erratic again