The Suzuki DR650 has the well earned reputation of being reliable as an anvil. I've owned two and both have been just great mules for my kind of adventure riding. For me that often means two or more weeks riding in remote places so reliability and sturdiness is far more important to me than shear performance. That said there are some well known common failure points for this bike - one of those being the ignition pulse coil (part of the stator assembly). These coils apparently fail to an open state (infinite resistance) from time to time without any warning and when that happens the bike will not run at all. Suzuki does not sell the pulse coil separate from the stator assembly but several aftermarket companies do. Regulatorrectifier.com is one and I ordered a spare coil for the very reasonable price of $35 + shipping some time ago. As far as I and the DR650 "collective" on Adventure Rider are aware there have been no failures of the aftermarket pulse coils reported.
Although some have had to do this trailside or in a motel parking lot, most people would agree that due to the complexity and need for cleanliness and special tools, replacement of the coil is best done in a garage. My aging DR650 (33K miles) was running just fine but since I'm about to depart on another extended adventure trip and since I hate being "that guy" - you know the one that everyone else has to wait on while he fixes his bike, I thought it prudent to replace my OEM coil with the (hopefully) more reliable spare coil in the comfort and convenience of my shop rather somewhere much less comfortable and convenient.
So here's the blow-by-blow account of the procedure.
First of all you're gonna need these parts - a replacement pulse coil and a new stator side gasket. Plus, of course, fresh engine oil and maybe some replacement screws (more later).
You'll need to support the bike in a vertical orientation. This procedure could be done with the bike laying on it's side but there is a risk of dropping the starter gear thrust washers into the crankcase during disassembly when doing it that way so I elected to do it vertical. I have a bike stand but because the skid plate has to come off and I knew I'd need something to support the side cover later I decided to support the bike on jackstands with a 1/2" rod through the swingarm. Another option would be to remove the cover with the bike on the side stand then lay the bike on it's right side for subsequent steps.
These parts have to come off before the side cover can be removed. And, of course, before you start to remove the cover you should drain the engine oil.
There are eleven 6mm bolts securing the cover. They are all the same so no worries about mixing them up
After removing the bolts, the side cover should come off. If yours has never been removed there's a good chance the gasket will stick to both sides and will tear apart. My bike is a '99 and I had this cover off a few years ago when I bought it to install the starter torque limiter so my cover simply pulled off with no resistance. I have not unplugged any wiring from the connectors under the seat so here I have just laid the cover over on it's "back".
Notice that my starter gear train came off with the cover. Yours may or may not. If it stays in place on the engine, no problem - just leave it there. If the gears come out, carefully observe how they interact and the order of assembly of the parts. Also BE SURE you do not lose the two little thrust washers on the torque limiter gear. You can see these washers in the photo below. These are the small parts that can fall into the crankcase ruining your whole day.
You'll have to remove the old gasket if it's still intact or if yours came apart this would be the time to clean up the surfaces for reassembly. This is not a pleasant task and you must be careful not to damage the mating surfaces. Read that to say DO NOT use a wire brush or metal scraper. Some people use chemical gasket removers with success. No matter how you do it you'll want to end up with smooth, clean mating surfaces on both sides. As you can see mine came off in one piece but was very brittle and broke when I tried to remove it from the outer case. I expected that and had a new one on hand.
So now we're ready to remove the old pulse coil. You're going to have to support the outer case for the next step. Here's the arrangement I used.
To actually remove the two JIS screws holding the pulse coil in place you're gonna need more than just a common screwdriver. Enter my prehistoric Vessel impact screw driver. It only took a single good 'whack' to break these loose but people who've tried to do it without an impact driver report they are very difficult to break loose.
With the screws removed the pulse coil is free to move - you can see it at the top of the picture below. Note that underneath it is a retainer that locates the wires from the generator portion of the stator. Be sure and reinstall that properly.
So, I'm thinking at this point, if I ever need to do this "in the field" I probably won't have my handy-dandy Vessel impact driver and since there's no problem with clearance here, I should just replace those JIS screws with something I can remove without special tools. The OEM screws are 5mm x 10mm with an 0.8 thread. A trip to the the great little hardware store 10 minutes from my house and I scored some 5mm x 12mm socket head screws in the correct thread. I didn't notice the depth of the holes before leaving so I bought spit washers too just in case.
It turns out the hole is plenty deep to accept to 2mm of extra length so I didn't end up using the split washer - just some blue Loctite.
FWIW, the new part is very similar but not identical to the Suzuki OEM part
Here's my new coil bolted in place with the new socket head screws. Nice. These will be far more easily removable if I ever have to do this again. The removed OEM coil checked out within specs (220 ohms) and will get packed with my other spare parts for the upcoming trip.
So, now you have a decision. The replacement coil from regulatorrectifier.com has long enough wires that you COULD snake them all the way up to the connector at the CDI and attach them there.
I was still thinking that I might have to do this again someday in a less than perfect environment and, since I'm handy with a soldering iron, I decided to splice the wires outside the case but in an accessible location lower down. I split the plastic insulation/outer wrap a short distance then cut the blue and green wires here.
Then I pulled the old coil's wires back through the grommet and pushed/pulled the wires from the new coil through. This was easier than I expected after I smeared a little oil on the new wires. Note for future reference the shape of the grommet and the place it fits into the outer case. When you reinstall everything you'll want the little ridge on the grommet to fit snuggly into to groove in the case.
Okay then, just a bit of magic with the soldering gun and some heat shrink tubing and viola! it's in. The instructions that came with the new coil said to connect the red wire to green one on the harness and white to blue but it also noted that sometimes it was necessary to reverse polarity. I figured the odds were better than 50% so I just followed the instructions and fortunately after reassembly the bike started right up. At this point I pulled the plastic outer insulation back over the new connections and then taped the split section with electrical tape.
Assembly is in the reverse order. The alignment dowel (circled below) may stay in the inner case or it may come off with the outer case as it did here. It's just a press fit and although it's not essential I find it's easier to align everything during reassembly if the dowel is installed in the inner rather than the outer case. It's easy to pull it out (might need pliers) and push it into the other side.
Assemble the starter gears in the inner case.
Place your new gasket and carefully slide the outer case back on
being careful to properly engage the gears and to not
damage the gasket. FWIW, I always lightly grease both sides
of the gasket and they seem to release easily next time.
Remember to keep up with the little torque limiter thrust
washers! Also the eleven 6mm outer case screws torque to
only about 5 ft-lbs. That's just snug. Don't strip these!
Just for reference here's another owners
experience with this same project: PulserReplacement.pdf
Good luck!
TN2Wheeler 8/18/2015