Yet another DIY EFI project - DR650

So first I need to say thanks to the DR pioneers, mx_rob , Head Trama. wildwestsydney, and msiddalingaiah. :bonk::lol:

I would never have had the guts to start this project, or maybe even think of it if not for their efforts to not only do it, but also post about here for all of us to learn from. As you will see, I borrowed heavily from their work. My goal was to find the simplest path to fuel only EFI operation and maybe add spark latter. And also to minimize the down time, and most of all to not mess up my bike. The bike is running OK now but I still have a long way to go on tuning and several minor issues to solve.

I started with a 2008 DR-650 with some mild upgrades. Opened air box, DJ jet kit, tuned with an installed wideband O2 sensor and AFR gauge, GSXR exhaust, and a JE piston. Basically it ran great, had lots of power, got great gas milage, was still stone reliable and needed nothing. So of course I had to screw with it! :lol:

This will be a somewhat long and involved post so I plan to do it in installments. So I guess the logical place to start is the fuel system. TB (Throttle Body), Injector, fuel pump, fuel pressure regulator, and plumbing.

After reading (and re-reading) Rob’s epic post, the selection of the TB and other fuel components was a no brainer. I shameless copied Rob’s work and sourced a LTR-450 quad TB, pump, fuel pressure regulator from ebay. I also followed his lead and picked up a complete wiring harness for the LTR-450 quad that not only gave me all the connectors but also included relays, Inlet Air Temp sensor, and MAP (Manifold Air Pressure) sensor. But I didn't get the CLT sensor.

The TB is 42 mm and came with the injector and TPS (Throttle Position Sensor). I earned from Rob’s post that the injector is rated for 24 Lb/HR and is more than adequate for the DR-650. The TB is a little shorter, a little larger at the intake manifold side and a little smaller at the back than the stock carb. So again following Rob’s lead, I chucked it up in my ancient lathe and turned down the front to fit the stock DR manifold, and made a spacer for the back to match the carb dimensions for both length and diameters front and back.

Here are some pictures:

Turning back spacer in the lathe:


Finished TB with rear adapter in place:


I didn’t have the nifty tab on the frame that Rob’s bike has (mine is a non-California type) and that he used to mount the fuel pump, so I had to make a clamp style mounting bracket from 1/4” aluminum. Ugly but it seems to work.

Here is a picture of the mounted fuel pump.


The fuel return line from the pressure regulator was a bit of a problem. I didn’t want to drill holes in the stock steel tank and also I wanted to avoid using a “T” back into the primary fuel line for fear of having the fuel get hot as some others have experienced. So I have been thinking about a Clarke tank for some time to save weight and gain a little more fuel capacity, and now I had a good excuse. I like the Clarke best mainly because I think it looks better but the IMS may have been a better choice as I believe it comes with two petcocks and would not require any additional holes. I did drill a hole in the bottom side of the Clarke but up high directly below the filler cap, and installed a 3/8” brass fixture. I sealed it up with plastic compatible epoxy. So far no leaks but time will tell. The bottom side of the fixture has a 90 degree elbow to a barbed fitting for the fuel return hose. These are available at any hardware store.

Here is a picture looking into the tank filler with the cap removed.


Here is a picture from the bottom of the tank showing the barbed fitting.


One of the key factors for me was being able to remove the tank to adjust valves and such without having to drain it. With this rig I can still do that as long as the tank isn’t too full.

High pressure fuel is nothing to mess around with so I wanted to stay with Suzuki factory fuel lines if at all possible. Ebay to the rescue! :smirk: There are always a bunch of them on ebay from various Suzuki models for around $20 each. I found some that work OK but they are now twisted in ways they were never meant to be twisted. . . I built a small portable wood mock up of the bike’s frame section around the motor area so I could hook all the fuel components up and take it outside well away from house and the bike for a test run to make sure it all worked and there were no leaks. That way I could fairly safely test using gas and not have to fool with other fluids and then purging. Burning up the house, the bike, myself or all three would be considered sub-optimal. . . So I hooked up a battery and a switch with a long wire so I could turn it on from a distance and watch for awhile. But all worked well with no issues, leaks, or flames. :bonk: I t is all installed on the bike now.

The fuel pressure regulator is not really mounted yet and just hangs from the three stiff hoses up under the TB. (again like Rob’s) But it can’t really go anywhere or bang into anything. You can see it in this picture behing the wideband O2 sensor, just kind of hanging there.


Well that is about it for the fuel stuff. Much more to follow.


Edited by jaeger22


There are several sensors that are needed. IAT (inlet air temp) CLT (Coolant Temp), TPS (Throttle Position Sensor), and MAP (Manifold Absolute Pressure). Also I wanted to tap into my Innovate wide band O2 sensor so the ECU could read AFR and make adjustments in real time. Using the IAT, TPS, and MAP from the LTR 450 made that part of the install much simpler. I just installed the IAT sensor into the front of the air box, tie wrapped the Map sensor to the frame on the right side and ran the vacuum line to the TB, and the TPS was already installed in the TB. So I then just needed to hook up all the wiring.

Here is a picture of the IAT sensor mounted in the air box.


And this is the MAP sensor tie wrapped to the frame on the right side.


The CLT (Coolant Temp), was a bit more of a problem. I picked up a standard GM sensor and connector off of Ebay and installed in the cylinder head on the right side. I just drilled a hole the size of the sensor probe through the top three fins and then opened up the top one and cut threads to match the ones on the sensor body. I inserted a couple of steel spacers in between the fins and around the probe to help protect it from air flow. (Black thingies)

Here is a picture of the sensor mounted:


Unfortunately I underestimated the criticality of this sensor. The Warm Up Enrichment (WUE) is my biggest issue now because this sensor gets too much air flow and cools off too much as I ride. Rob actually theorized that this would be a problem and made a brass holder on the back of the cylinder that I expect worked better but I think he still saw the issue. I foolishly assumed that I only needed to know when the engine was warm so it didn’t matter much. :lol: But the DR, being air cooled, takes a long time to fully warm and that time verse temperature graph looks very different depending on conditions. Not only air temperature but how you ride it. If it is left sitting at idle on a warm day, it gets very warm very fast and the fin mounted sensor tracks well. But if I head down the road right away on a cool wet day, the sensor may never reach the WUE cut off, even when the engine is fully warm inside and in need of leaner a mixture. So for now, I just have the WUE cut off temperature set low. Basically the problem seems to be that the sensor is mounted in the fins and the fins cool off much faster in rapid air flow than the inside of the head which is what we really need to know. (Yea, I know, you dummy, they are COOLING fins! :lol: ) So I have a lot more tinkering to do to get that worked out. :bonk: I have some thermistors on order from DigiKey and I am thinking along the lines of mounting one in the valve cover. An ideas?

I mapped the IAT and CLT sensors by sticking them in ice water then warm, and then hot water with a thermometer and recorded the resistance of each at several points. The Tuner Studio software that is used to load and modify the MicroSquirt has a tool that lets you built the temperature response table for each sensor using these degree/resistance inputs. For the MAP sensor I relied on the measurements Rob took and posted and only had to tweak them a little to get the MAP to read the correct 103.3 kPa for my 60 feet above sea level location here in Orlando.

The TPS was easy to calibrate using The Tuner Studio software. You just tell the calibration tool when you have the throttle closed and then when it is WOT, and it reads those two locations and builds the map.

I installed the sensors (except the TPS) and wired them up to the MS on the so I see how they worked while still running on the carb. I also got the Tach trigger working in that configuration and that was an adventure in itself. I will talk about that in the next post.

Except for the WUE issues, the bike is running well and it is amazing to watch the AFR meter as I ride and see it just nail the AFR in every cruise condition. :bonk: And I can use the key board to quickly set the desired AFR to anything I like and the ECU will adjust on the fly and match that setting. Sooo cool. . . :lol: .With the old BST carb it was always a compromise. In my bike, even with the DJ needle that I expected to go rich at higher crusie RPM. :lol: It turned out it wasn't tapered enough! :smirk: It still got leaner the faster I went until it started to get fully onto the main jet. Now with the EFI, it is dead on at any speed. :lol:

Also the AFR meter is much more consistent. It still jumps around a little but nothing like it did with the BST.

Edited by jaeger22

Tach Trigger

Getting a good trigger on the DR is a bit of a pain because the stock CDI system will not allow you to just tap into the negative side of the coil. The voltage going to the coil is around 400 volts and can fry the MS if you are not very careful. Also the pulse is negative going just to make things more complicated.

I first thought I could make the stock VR sensor work but ran into more problems there. The DR has one very long tooth, then a small gap, and then another long tooth. The VR sensor only detects changes so gives a positive output when it first encounters a tooth then it goes back to zero until the end of the tooth where it gives a negative pulse. (The output is really AC so the polarity of the pulse may be reversed depending on which wire you are looking at.) So we get a signal on the o-scope that looks sort of like this.

My crude drawing:


Sorry I didn't take any picture of the scope but it too much of a pain to hook back up now. The signal is readily detected by the MS but it gets really confused by the pattern. It is set up to accept a single pulse per cycle or in most cases 36 or 60 tooth wheels with one or more missing teeth. The multi tooth wheel (Like Rob built) will allow precise control of the spark timing. But I am just doing simple fuel only for now.

The solution I ended up using came from msiddalingaiah’s DR-350 EFI install. I just wrapped about a dozen turns of wire around the body of the coil core where it sticks out of the coil windings to form the mount. I grounded one side of the winding and the other side provided a nice fairly clean signal. The beauty of this approach is that once you get working, it is consistent. The pulse width and amplitude do not change with RPM like most if not all of the other possible signals. I tried several passive conditioning circuits with resistors, capacitors and zener diodes, but anything I added loaded the signal down too much. I ended up just wiring the winding output directly to the MS OPTIN line. It has worked perfect so far. No drop outs or resets at any RPM that I have seen so far.

The MS software has a filter built in that will block out any additional triggers for X Msec and I have it set for 7 Msec. Seems to work well for me. There is some ringing in the signal but this filter avoids any double triggering issues. :smirk:


Very nice work John! :bonk: Lots of fun tinkering with FI. The potential is the best performance and best fuel economy. As far as the CLT goes that is certainly an issue with a air cooled engine. My copper Rube Goldberg set-up doesn't work properly when the temps drop down. The current FI project I'm in the middle of for the DR650 uses a simple bolt attachment point for the sensor. Have not got the new system figured out with the tach signal (stock VRS) because of the same pattern issue but we are trying to get it to work. So I don't know if that CLT is going to work out or not. One thing is it's not bolted to a fin so the temps should not vary as wildly... we hope. As far as our tach signal we always have the msiddalingaiah coil wrap option but we'd like to use the available CDI unit this FI system has as an option so using the stock VRS would be optimum if we can make it work. I'll keep a tab on your progress. :smirk:

It's great to see more EFI projects!! This is what I ended up with for my CLT sensor:


The copper ring was donated from a Trail Tech head temp gauge, but you can fab your own without much trouble.

It has worked really well for me so far. I installed a 3k thermistor from Digi-Key. The measurement compares well with a common IR temp sensor.

As for tach signal, I had some issues with dropouts using the wire around the ignition coil trick. I eventually went with a custom circuit. Since then, a helpful DR brother donated a flaky CDI. I was able pull it apart and reverse engineer some of the input circuitry. Does the DR650 have a tach? If so, the signal going to the tach is a nice clean square wave that should do the trick. On the DR350S, it's a white/red wire. If you have that wire in the harness, take a look at it with your 'scope. I think wildwestsydney might have used that signal on his build. Either way, if your setup is working, go for it!

It sounds like you have a good handle on the project. Good luck!

Edited by msiddalingaiah

Thanks Rob! Good to hear from the master! :lol: I just found your new post on the other forum, but have not got all the way up to date yet.I lot to read! But very interesting so far.

I gave a lot of thought to trying to make the stock VR signal work but finally came to the conclusion that I probably could not make the MS software work with it. Either the standard or the MSExtra. But I am toying with the idea of writing my own code. I am not at all sure if I could get that to work but it would be cool if I can. :bonk:

On the warm up issue, there were some good ideas that popped up on your thread for installing a thermistor in the valve cover. I am thinking of something along that line. I will let you know how that works out.

It is not a big problem now as I set the point where WUE is down to 100% (no enrichment) to 145 degrees. Being in Florida, it has to get real cold here to drive the reading below that. It only causes me an issue now in that range between when WUE has stopped (reading temp >145 Deg ) and then the engine is really warmed up enough to idle with enrichment. I have the LTR-450 warm up-extra air- plunger hooked up the DR choke lever and that works great. It allows me to push up the idle speed for start and warmup. I didn't think it would work because the MS doesn't know about it and can't adjust the fuel. But for reasons I do not fully understand, it works like a champ. The AFR stays about the same and the RPMs go up as I pull the lever back to a max of about 2500 RPM idle. The I can then back off as it warms up to just enough to keep it in the 1600-1700 range. But I still want to get the WUE right so I don't have to mess with it as much. :smirk:


msiddalingaiah! Two masters in one night! :lol: Thanks for the help.

Yes I thought about the ring and I ordered the exact thermistor you recommended in your original post from Digi-key. I think that would work well. My only hesitation is that I already have a ring sensor under one plug for the Vapor Tech. I had to grind away some of the head material to get that one to fit, The other plug is recessed even more. But it still may work with a little cutting. I kind of like the idea of the oil splash with the sensor in the valve cover idea. Seems like it may warm up a little slower but stay right with the intake valve temperature after that. I ordered several thermistors so I can experiment.

No the DR650 does not come with a tach. :smirk: I even scoped all the unused pins on the CDI in the hope that the CDI unit might be a standard for Suzuki and generate the tach signal but that it just was not used on the DR650 due to no tachometer. But no joy, they were all dead pins. So far I have had no issues with noise or drop outs that I have noticed. But I will keep an eye out.

Thanks again for the ideas and for the ones you posted way back in Rob's thread! :bonk:


MicroSquirt installation, wiring, and tuning.

So the next problem is, where the heck am I going to put the MS? I got lucky here because a couple of things came together. Pro Cycle offers a new lithium battery that is much smaller and lighter than the stock battery and provides MORE cranking amps. So with a few small modifications to the battery box maybe the MS could fit in the freed up space? Unfortunately after careful measurements, I determined the MS would not quite fit. But by the time I ordered the MS they had just come out with a new version (V3) that has the connector coming off at a 90 angle resulting in a slimmer body and with this version it will now just fit. :smirk: So I ordered the lithium battery! As a side benefit, the new battery and new Clarke tank saved about 10 LB, so with the fuel pump and fuel pressure regulator added, the bike is actually lighter after the EFI project than it was before! :bonk:

This is what the MS kit looks like as it came from


And here it is installed:


The new lithium battery is under the left (as shown in this picture) terminal strip which supplies the MS and all my other farkles. (GPS, Vapor dash, O2 sensor, Headlight relay upgrade) The MS is wedged in right behind it with foam padding in between. The top right terminal strip is just for the MS grounds. Half of that ground terminal strip is just for separate signal grounds. This is to help eliminate electrical noise and seems to work as so far I haven’t detected any noise issues.

So with the Fuel system checked out on my test rig and good Tach signal, the MS installed and most of the wiring done, it was time to take the plunge. Off with the carb and on with TB and final wiring.

OK so I thought it would go quickly once I got this far. . .NOT! :lol: I could not get it to start. For some reason I never really figured out, the MS never when to cranking mode and would not squirt any fuel. I had good RPM and all the sensors except the O2 were working right. I downloaded an older version of the source code (I could not find 3.7.7 source) to see if I could figure out what it didn’t like, or what it was missing to set cranking mode, but it looked to me like it only wanted to see RPM above zero and less than the max cranking mode RPM limit which I had set to 600. I was getting around 425 to 475 or so RPM while cranking. I tried every setup configuration I could think of but never got cranking mode set. I think the B&G 3.7.7 code that comes in the MS is just too smart for my simple setup or I am just too dumb to trick it into doing something simple. I know, most likely the latter. :lol:

There is an alternate firmware/code for MS available from a different on-line community for free called MSExtra. It is a little different and has a lot of cool features. So I downloaded and installed the MS Extra code just to see if that would make a difference. They even provide the source code and the build environment and encourage those wanting to, to make their own code changes and recompile it. So I was able to get up to date source code for that SW to help me troubleshoot. But I didn’t need the source code (so far). MSExtra code has a mode select in the setup for Fuel only and that worked right off. I got cranking mode right away and my O2 sensor input worked just fine. About 10 minutes after getting the new code installed I got to hear it run for the first time! Man that was a kick!

So I am thinking now that I have it running, in a day or two I will have it all tuned up. Again NOT! Yes I got it to run well enough that I got to ride it around town but it had all kinds of issues. The biggest one was stalling sometimes when I went back to idle. That is very annoying in traffic. But by going through the process of riding with the laptop strapped to the back and logging data, and then tuning the results, it got better and better. There are bunch of things to play with like Acceleration Enrichment (AE), overrun cutoff, EGO (AFR correction) Warm Up Enrichment (WUE). As I get each dialed in, it continues to get better and. It is now, after a month of tuning and trying different things, running very nicely, with far better and more consistent AFR readings than I could ever get with the BST carb. But I still have a few things to play with that should make even better.

So in summary, this has been and continues to be one of the most fun and challenging projects I have ever done. I can’t say all the time and money was worth it for the minimal performance gains, but for the enjoyment, heck yes! I am already thinking about spark control next. The experts say that is where you find the most performance gain.

Thanks for tagging along on this long winded write up! :bonk:


So in summary, this has been and continues to be one of the most fun and challenging projects I have ever done. I can’t say all the time and money was worth it for the minimal performance gains, but for the enjoyment, heck yes! I am already thinking about spark control next. The experts say that is where you find the most performance gain. Thanks for tagging along on this long winded write up! :lol:


Congrats on pulling this off! The education value alone has to be worth it all. Good to see young engineers digging in and building things ... and inventing. :bonk: Our country really needs to see more guys like you putting in the hours. :smirk::lol:

Not sure where you ride your DR650 or what plans you may have for it. I do longer dual sport rides and rides to Latin America. My bike is fairly beat up and not pretty to look at. But I know it pretty well and can do most roadside repairs or diagnosis in minutes ... usually :bonk: So, most times, I appreciate the dead simple elements on the DR650. I'm pushing up on 55K miles now and view the DR650 as more a really good, reliable tool. Not a SUMO or race bike ... just a simple and reliable travel bike that anyone can fix ... anywhere in the world.

Looking at your final pic showing the wiring to your various components confirms this is something I never, ever want to see when I pull the seat off! :lol:

But it takes all kinds ... and I certainly admire you (and all the engineers out there) who have dug in and done some really interesting projects on the DR650! Kudos!

Hope you can make your bike a good reliable ride that you'll be able to do some exploring on. The DR's are actually pretty good at this ...

Edited by 54321

Thanks 54321! But I wish I could claim to be a "young engineer" Engineer yes. Young...not so much! :smirk: Way over the hill but still love this stuff and riding.

Not sure where you ride your DR650 or what plans you may have for it. I do longer dual sport rides and rides to Latin America. My bike is fairly beat up and not pretty to look at. But I know it pretty well and can do most roadside repairs or diagnosis in minutes ... usually :lol: So, most times, I appreciate the dead simple elements on the DR650. I'm pushing up on 55K miles now and view the DR650 as more a really good, reliable tool. Not a SUMO or race bike ... just a simple and reliable travel bike that anyone can fix ... anywhere in the world.

I hear you about the simple and reliable for long rides. I have a DL-650 V-Strom that is my long distance and two up with the wife bike. I have left it stone stock except for comfort mods like seat, handles bars, lower pegs. larger windshield, heated grips, GPS, . . . OK the motor is stock anyway! :lol: I have 80K miles on that bike now including two coast to coast trips. The long way, FL to Washington state and back. Also one Orlando to Denver and back and one Orlando to Tulsa and back. Stone reliable, comfortable and cheap to maintain. :bonk:

I love the DR but not for long distance unless like you I was doing duel sport. My DR is my "play" bike. Mostly around town, back roads and a little dirt. (I live on a dirt road so couldn't avoid it if i wanted to) So in that roll I can afford to tinker without too much fear of one of my mods going awry when I am 100 miles from the nearest civilization. Still it is my main day to day ride so it has to be reliable. So far though the DR has never failed to get me home even with all the abuse I give it.

Looking at your final pic showing the wiring to your various components confirms this is something I never, ever want to see when I pull the seat off! :bonk:

LOL! I hear you there also! It is not really as bad as it looks. On my to do list,"clean up the wiring".


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