Vehicles

xs1100 - new ignition coils, changed oil, repaired pickup coil wires

This page represents the culmination of a heck of a lot of troubleshooting. Finally the bike is fully functional again. I can't wait to take it for a spin.

The Problem

The bike hesitates across all RPMs to the point that it is not safe to drive. This started a couple years ago. At first it was intermittent however last year it finally started happening all the time.

What Didn't Fix It

First I cleaned my carburetors. The problem seemed to go away for a bit but them come back. At this time the problem was still very intermittent. Next I cleaned my air filters. Then I cleaned my petcocks and replaced my fuel lines and added two in-line fuel filters. Non of this helped so I cleaned my carbs one more time. Nope, still a problem.This is where I parked the bike for the season. It was also around this time I bought the Yamaha FJR to be my daily driver. The problems I was having with the xs1100 certainly contributed to me buying the FJR but I probably still would have bought it even if the xs1100 was running perfectly.

What Fixed It

Both of my dual output coils were out of spec. The primary resistance was 25k ohms when it should have been 15k ohms. I replaced them with the green coils from Mikes XS, part number 17-6810. Even though I have had bad experiences with Mike's products in the past, the common consensus is that these coils are the best you can get for the XS1100, even though they are sold for the XS650. I also replaced the spark plug wires at the same time.

Once that was done I noticed that the bike started up extremely quickly. Alas, it still had the stuttering problem, though it was not nearly as pronounced. I would probably have felt comfortable driving the bike on the highway at this point but I knew it wasn't 100% yet.

Thank goodness for the tech tips and forums over at XS11.com. They recommended checking the wirings running from the pickup coil. These wires are subject to bending as the ignition advance mechanism moves. Over time these wires break, even though the rubber (or maybe silicon) casing is still intact. I checked the resistance on my wires and sure enough, 3 of the 4 wires had splits. They read okay at first but any movement broke the connection.

I soldered in replacement wires for all 4 wires and viola, the bike is happy again and running great.

Mikes XS Green Coils

While installing the new coils I ran into some issues. I want to cover some of the things I learned.

  1. The left coil fires cylinders 1 and 4. The right coil fires cylinders 2 and 3.
  2. The ignition system fires both cylinders at the same time, even though one of them is on its exhaust stroke. This means that the spark plug wires for 1 and 4 are completely interchangeable. You can put the #1 wire on the #4 cylinder and everything continues to work great. The same goes for #2 and #3. 
  3. The green coils have two screw in wire attachment points. One wire is for positive, the other is negative. There is no polarity on the coil. Either wire can go on either screw. Swapping the two wires has no effect on operation.
  4. The new green coils are about the same size as the old coils but the wires are all oriented differently. I ended up using small 90 degree brackets to mount the new coils. The brackets had to be bent slightly to make it all work but in the end there is still plenty of space around the new coils for cooling purposes.

Pictures

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just for reference, the mapping of pickup coil wires to what you get at the 4 pin molex connector
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two new wires installed on upper pickup coil
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all 4 wires were routed differently to try to distribute bending load due to advance plate twisting
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two new wires installed on lower pickup coil

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