Installing FI cbr125/250 throttle bodies on CL350 using microsquirt ECU

Alex18701

Member
So, I have purchased two cbr250 throttle bodies and want to use them on my cl350 because it would possibly improve the performance as well as to see what the power gain would be compared to a carbed system. I figure cbr 125 throttle bodies might work best but all I found were cbr250 throttle bodies because cbr125's were not available in the US market. I figure as long as i install smaller injectors it should work fine. I've also read on multiple forums that carbs require a precise size carb bore to engine cc's because that's how the fuel is delivered vs throttle bodies FI where it is being electronically delivered and doesn't rely on the vacuum to completely deliver the fuel. The (cbr250)throttle body bore size is 48mm OD. and the ID. is 39mm. what do you guys think, will the bore size affect performance if so should i get some cbr 125 throttle bodies which are 30mm ID., also looking to use a ECU such as a micro squirt to control the FI system as well as ignition system. Let me know, any input is appreciated and really looking forward to getting this completed soon.
 
Last edited:

Rat_ranger

Active Member
I've got a microsquirt and gsxr600 throttle bodies and chevy LS2 coils on my XS650. They are 38mm ID and fit in the carb boots for a bs34 carb. The bigger the throttle body the worse the transition performance will be. It'll be hard to have just small changes in rpm with small throttle movement.

You might consider something like these( https://www.ebay.com/itm/1983-KAWASAKI-GPz1100-Throttle-Body-Fuel-Injection-/174212503038?nav=SEARCH ) they are supposed to be 34mm ID, and would give smoother throttle response.

you'll need to figure out a fuel pump, EFI needs 43psi. Simplest way to control the ecu is replace the points/advance unit with a 36-1 trigger wheel. Tuning is easy with the tunerstudio program.

don't forget to look at the msextra page for info on the microsquirt and how people have used it.

Here's a couple short videos of my XS
 

teazer

Well-Known Member
DTT BOTM WINNER
What about a set from a GSXR600 K1? I think they are 34mm or so and have more modern injectors. They also have a secondary throttle plate which could be removed or programmed.

 

Rat_ranger

Active Member
The gsxr600 k1 throttle bodies are 38mm, but they are easy to respace for about anything. Also if being respaced it's much simpler to just remove the secondary throttle valve. They use 1 long shaft to connect them, where the main butterflies are each on their own shaft.
 

Alex18701

Member
Thanks for the info Rat_ranger and nice setup you got there, I'll take your advice and go with a smaller throttle body. I have a set of cbr125 throttle bodys that I ended up ordering with a 30mm ID. hopefully, I can get it put together soon enough but the programming and efi electrical system will be something new to me. Will order the right fuel pump, I already have a electronic ignition system and worked well with the previous carburetors the bike ran on but I may do the 36-1 trigger wheel setup. will keep everyone up to date on any updates.
 

cxman

Active Member
DTT SUPPORTER
what have you done to the charging system so it can keep up with the fuel pump and injectors
when it really does not charge much below 3 k rpm and between ignition pump ecu and injectors
and head light and tail light you have a good draw going
 

teazer

Well-Known Member
DTT BOTM WINNER
Sonrier has an upgraded alternator I believe. I think it was designed for the 360s but probably fits 350s as well. I have no idea what the output is or how it compares say to a Lucas RM23 which Cycle-X sells as an upgrade for CB750s and 450s.
 

Snout

Active Member
I've got a microsquirt and gsxr600 throttle bodies and chevy LS2 coils on my XS650. They are 38mm ID and fit in the carb boots for a bs34 carb. The bigger the throttle body the worse the transition performance will be. It'll be hard to have just small changes in rpm with small throttle movement.

You might consider something like these( https://www.ebay.com/itm/1983-KAWASAKI-GPz1100-Throttle-Body-Fuel-Injection-/174212503038?nav=SEARCH ) they are supposed to be 34mm ID, and would give smoother throttle response.

you'll need to figure out a fuel pump, EFI needs 43psi. Simplest way to control the ecu is replace the points/advance unit with a 36-1 trigger wheel. Tuning is easy with the tunerstudio program.

don't forget to look at the msextra page for info on the microsquirt and how people have used it.

Here's a couple short videos of my XS
That is a nice running XS. What did it hit for HP numbers?
 

Rat_ranger

Active Member
45hp and 36tq with a hurt cylinder. It had a wrist pin circlip fail on the dyno. Once I get a house again it's going 700cc big bore.
20190820_142658.jpg


LED lights reduce draw by a good bit. The ECU itself doesn't draw much, biggest draw will be pump and coils. I'm using LS2 coils, they play well with the ECU and provide a real good spark. For a pump there are some decent self contained units from ATVs, they mount seperate from the main tank, have fairly low draw compared to automotive units, and have a swirl pot so the pump stays cooler being inside fuel. I went with a custom intank set up for space, but if you keep sidecovers the atv pump should be the simplest way to go.
 

Snout

Active Member
45hp and 36tq with a hurt cylinder. It had a wrist pin circlip fail on the dyno. Once I get a house again it's going 700cc big bore.
View attachment 224959

LED lights reduce draw by a good bit. The ECU itself doesn't draw much, biggest draw will be pump and coils. I'm using LS2 coils, they play well with the ECU and provide a real good spark. For a pump there are some decent self contained units from ATVs, they mount seperate from the main tank, have fairly low draw compared to automotive units, and have a swirl pot so the pump stays cooler being inside fuel. I went with a custom intank set up for space, but if you keep sidecovers the atv pump should be the simplest way to go.
Cool. Did you do the kit from Microsquirt that you assemble? I was looking at their stuff pretty hard a few years back for a turbo project. It seems you can have endless possibilities for everything...triggers,timing,boost,coil style. Very smart stuff.
 

Rat_ranger

Active Member
I used a microsquirt, much smaller size wise, not as flexible but for a 2cyl it's full sequential. I had a MS2 V3 I built in a triumph spitfire with a toyota motor and individual throttle bodies, took about 6hrs to assemble, and it worked.

The little black box right at the back of the tail is the microsquirt. If you have space restrictions it's great. If you need the massive flexibility of the standard stuff it's not so great.
20180505_194011.jpg
 

der_nanno

Faster!
I always wondered, why the Microsquirt is still (from my knowledge) stuck at MS2? It's a lovely project though...
 

Rat_ranger

Active Member
It is still using the ms2 chip. I'm guessing it has to do with size. You can only fit so many components and don't really have room for the heat sinks of the full size megasquirts. It can be modded to a point, but for simpler stuff, such as a semisequential 4cyl, sequential 2cyl or batch fire v6/8 it works great. If you want to add launch control, flat shift, knock sensor, full sequential on 4 or more cylinders, boost control, etc then the full size units are a much better choice. Ms2 works great, ms3 with the ms3x expansion can do way more with less work, or if you want haltech level plug and play go with the ms3pro. I like the micro for the bike due to size and it fit my goal. If I did another car I would probably go ms3x, for a first foray into doing EFI the ms2 was great. I learned a hell of a lot, I just started with the basic build and did a few mods as I learned and never needed the upgrade of the 3 or 3x daughterboards. Plus if you stick with the build it yourself types it saves a bunch of money.
 

der_nanno

Faster!
I've been contemplating going with a MS3 to replace my current carb setup on the Turbo TR1, but I think we're a bit of course by now...
 

DTT Bike Of The Month Gallery

DTT Light or Dark

www.cognitomoto.com
https://www.townmoto.com
www.speedmotoco.com
www.jadusmotorcycleparts.com
www.lostapostle.ca/
www.sparckmoto.com
Top Bottom