I recently had the xs650 top end rebuilt. Once I reassembled everything I started the bike and was very disappointed to see that it was running like crap. I traced the problem down to a bad coil. I was reading open (no resistance) when I probed the secondary resistance. The primary coil resistance was still in spec. This was a surprise to me because the coil came with the Boyer digital ignition system I fitted so the coil was one of the newest things on the bike and had seen almost no use.
I did some searching on the new and came to find out that the coil, made by GIL, has a pretty bad reputation for quality, at least according to the 650 forum members. Whats worse is that a replacement GIL coil would cost $100+. I decided to get a different coil if possible but the problem was the boyer system was designed to work with a coil with a low primary Resistance, like the GIL with its 0.6 ohm primary resistance. This bums me out because all the other coils commonly available for the 650 are in the 2-4 ohm resistance area.
Eventually I found a xs650.com forum member who fitted a GM coil to his 650. He was using a Boyer. He got the idea from another forum member on xs650temp.com who built an entirely new ignition system for $19 by using junkyard parts. I didn't have to go that far but I was glad to see multiple people had success with this GM coil.
I headed to napa auto parts and ordered 1 coil for a 1990's Chevy Corsica. I got the cheapo one and it was only $28 brand new. That sure beats the price of the GIL. The new coil is not without it's share of problems though.
Its bigger, a lot bigger
It has a different ignition wire attachment method than the GIL. It has male rather than female connectors.
It is designed to plug into an ignition controller so there are no wire leads, just female connectors where + and – are brought in from the controller.
I figured I could find somewhere to mount the coil so #1 was okay. To address #2 I ended up buying a new set of wires for Corsica (set of 4). I then took two of the wires and cut them to length and attached my own screw own NGK spark plug caps. The wires are dark blue which is too bad. I wish they were just black. No big deal though.
As for #3, I could have bought the ignition controller off of ebay for pretty cheap then cut it up to get the wire leads I needed. I opted instead to just try your typical crimp on wire connectors to see if they would reach far enough into the coil to make contact. As it turns out, with minimal modification, the crimp on wire connectors work great.
I ended up mounting the coil a couple different ways before I finally found one that let me slip the gas tank over it. Right now it is held in place with zip strips. This allows the coil to rattle around as the bike vibrates (which is a lot) so I will have to come up with a better mounting solution.
With the coil in place, I then turned my attention to the carb boots. The boots them selves were actually in pretty good shape. The problem was that the vacuum plug pulled out of one of the boots. I tried gluing it back in place but it wouldn't stick. I found a site that sells extremely high quality custom carb boots for the xs650, JBMIndustries.com. I can say with certainty that their boots are pretty awesome. The carb wall is extremely thick and reinforced internally with metal so there is no more need for the external metal shroud.
I fitted the new carb boots pretty quickly. I hope they hold up as well as the company claims they will. Time will tell.
As long as I had the carbs off I adjusted the carb float level. I then remounted the carbs and fired up the bike. It came to life almost immediately! I then fine tuned the boyer timing and synchronized the carbs.
With that done, it was now time to go for a spin. I took it around the block and back. There were no signs of leaks and no obvious problems (i.e. the bike didn't explode) so I decided to go for a longer test ride. I put on about 10 miles on the bike, being careful to keep the RPMs below 4k.
The carbs seem to be dialed in perfectly. Overall the engine is working well. There was a little oil leak right where the oil feed pipe meets the bottom end. I tightened it up a little more, hopefully it takes care of it. The other thing I noticed was some weird rattling noises that were tied to RPM. I think they are all external to the engine. I think my coil that I zip stripped in place is rattling down there under the tank. I will have to secure that better. I also hear some sort of rattle from the back end. Not sure what that is yet but lets take it one thing at a time.
It was a blast to get out there on the 650 again. I had forgotten what a lightweight bike it is. I have been driving the xs1100 and FJR for years now. In comparison the 650 feels extremely nimble, but also very cramped. I had forgotten how close the bars are. I think new bars are probably in my future. Either way, I cant wait to get back on the 650 for some progressively longer rides.
PS: Here are some specs on the new coil.
Part Number: IC39SB
Primary Resistance: 0.4 to 0.6 ohms, typically 0.4 ohms
Secondary Resistance: 5.6 k ohms
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