EFI conversion


Active Member
Ok, as some of you know I have an XS650 that I am converting to EFI. I have it running and have even gone on a few short rides but have a good bit of tuning left to go. So this will be a basic write up of the steps I took to get to this point.

EFI needs a few things to work, An ECU, sensors, fuel pump, throttle body/bodies, and injectors. so here is a list of what I used:
ECU is a microsquirt from DIY Autotune.
Sensors: GM intake air temp, GM Manifold absolute pressure, suzuki throttle position, dubshop modified gm coolant temp, spartan wideband o2, allegro ats627 for "crank position"
Throttle bodies are respaced 02 gsxr600
Injectors are cbr1100xx blackbird injectors at 330cc/min
fuel pump is an aftermarket ktm duke 690, but looking at changing to an aftermarket sportster pump.
fuel rail is aluminum extrusion that I drilled with the right spacing.

I chose to use the trigger wheel at cam speed, this is a 2" 36-1 wheel mounted where the original advance mechanism mounted. It is picked up by the ATS627 mounted in a custom m12x1.25 aluminum bolt. Using the wheel at cam speed allows running full sequential without needing dual pick ups, which being rephased means needing sequential. a 360* twin or normal 4 cylinder can easily be set up with batch fire fuel and waste spark.

Fuel pump is important as you need 43psi of fuel pressure. You can use pumps from a few different ATVs as they are external and low current draw, but they take up space. I chose the more complicated intank route. I made a small housing for a ninja 650 fuel pressure regulator, and a bottom plate to allow everything to be inside the tank, this did require a 1.55"x2" hole in the tank. Some tanks will give you more space making it simpler.

For ignition it is simpler to run a "smart" coil. I am using a pair of LS2 coils, there are other choices out there but the LS coils are readily available and affordable.

On the ECU I am running msextra code, it has better support than the standard B&G code and all info can be found at msextra.com. So for wiring I followed the manual for the msextra, this is fairly straight forward. It takes 2 relays, about 8 fuses, and some planning to run the wires. I am using the metripack280 fuse boxes from cycleterminal, mainly for size. Relays are standard 4 pin, 1 is the main relay that powers lights and ECU with the key on, the other relay is turned on by the ECU and powers the fuel pump, coils, wideband, and idle valve.

I am using a PMA that outputs 200w, with all LED lighting. This set up gives me 13.1v at idle and while riding gets up to 13.8-14.1v depending on RPM. So the charging system is providing plenty of power to run everything and keep the battery charged.

Fabrication required on this would require having access to machine tools, or a friend that does to keep costs down. Parts I had to machine are as follows:
Throttle body spacers and secondary butteryfly block off, trigger wheel and mount to fit the cam, bolt for crank sensor, fuel pump mount, fuel pressure regulator and fuel rail. Velocity stacks are optional.

Once you have it all mounted up follow the manual on inputting the required info into tunerstudio to start tuning. You'll need to know the injector size, number of cylinders and displacement to get a rough fuel map, and I would find the timing curve for your engine and copy it for the ignition map. You will also have to have the "missing tooth" on your trigger wheel set about 90* BTDC. Now, you will want to start with Alpha N tuning, ITBs do not provide enough vacuum to make speed density work well. But the nice trick is once you have Alpha N tuned well you can datalog to find switchpoints for ITB mode. This lets the engine run speed density at low load which is smoother since it watches throttle position, vacuum, wideband and rpm to determine fueling, but switch to alpha n once you get out of the area speed density works.

I have about $6-700 into this, but I also have my own machine tools and a willingness to wait on good deals. You might be able to do it a little cheaper, or it could turn into a money pit. It really depends on how much you can do yourself, and how long you can wait for sales/deals. I chose to do this because I dislike carbs. I have dealt with single carb up to 4 carb set ups, cleaned tuned, balanced etc. on bikes and cars. I know depending on condition and care given to them they can vary from almost invisible they work so well, to a nightmare of always tweaking.

The pictures show the cam wheel and sensor mounted, as well as the right ITB with the throttle position sensor.
The sensor for the trigger wheel
fuel pump set up out of the tank
fuel pump in the tank, as well as the throttle assembly on the left ITB
and all the wiring under the seat.



That's some nice work there! Many moons ago, I rewired my Iranian neighbours' Transit van with a MS1 and was pleasantly on how easy it was and how quickly it yielded dramatically better results in fuel consumption and overall running quality.


Active Member
Thanks! I've had a few questions about it on facebook and other forums so I thought I would do a basic write up of just the efi. I hope it gives others a good idea of what is needed and the kind of shopping list it entails.

I have an MS2 is a toyota powered spitfire, I did the entire DIY set up where I had to solder the board together. It really is simpler than I would have thought, and with the microsquirt it is small enough to hide. I honestly think with patience almost anyone could make the conversion, and your right that once dialed in it can make a big improvement.


Active Member
I've only put about 20 miles on it so far, so it still has some tuning to go. But other than tuning hiccups it runs and rides well. I'm working on tuning out a hiccup at low rpm right now.


Active Member
To anyone that is thinking about an EFI swap, if the engine runs ok then starts to need huge amounts of fuel added, clean the injectors. I started having issues and turned out the injectors were partially clogged. Swapped in the spare set and all is good.
totally cool project, how hard is it to configure the MS program? do you just tell it how many cylinders, crank angles etc? Does it also control the ignition timing?


Active Member
Configring the ecu is actually pretty easy. The program used to tune everything is called tunerstudio, and is very simple. It does control ignition, I'm using chevy LS coils for the ease of wiring. There are a few pieces of info needed, displacement, number of cylinders, size of injectors, oddfire angle if needed, and the offset from the trigger wheel tooth 1 and tdc cylinder 1. If there is a basemap from someone else it helps.
will it generate a rough basemap to start? I have tuned bikes with a ride along datalogger connected to the tps, afr sensor and tach and it made tuning pretty quick as long as I could actually get out and ride the bike


Active Member
It will for the fuel, it will not for the ignition. For the ignition I looked up the advance curve for the stock setup and copied that. But the rough basemap is just that, rough. I had to do a few short rides getting datalogs to correct it in to where it would pull all the way to redline in gear. Now that I am closer autotune will bring it even closer, I just have to ride with a backpack to carry the laptop. You can use android devices as well, but I don't have a bluetooth adapter.

DTT Bike Of The Month Gallery

DTT Light or Dark

Top Bottom