Throttle body questions

[dj423]

Been doing my 'homework' on doing a big bore on my 22 CT125, got a LOT of good info searching various threads here. Where I get confused is with the 5pin vs 3pin MAP/IACV/TPS lingo. From the service manual I see the CT has a 5 pin connector for MAP and TPS, but only three wires. I am assuming the TB's are different from the Grom ones I see all over the web. At least that is the vibe I got doing a lot of reading.

I was looking at this Yuminashi 30mm here: https://www.yuminashi.eu/30mm-throttle-body-upgrade-set-z125-pro-pcx125-150-adv150-etc/

Is anyone running this TB on their CT125? I know m in sc mentioned the clipping point 26mm TB on webike, so that is a possibility and would probably meet my needs.

A little backstory, the kit I have is for a Grom, it's the Koso 170cc kit with the 4v head and intake manifold, with a Koso oil pump and chain tensioner. So I /think/ it will work, but still doing research on how to deal with the TB and intake since they are different from the Grom stuff. For engine management I plan on running an EFIE at the very least, and possibly the aRacer mini-x ECU once I confirm which ECU my bike has. Cassie at Cameron Jones mentioned they hope to soon have tunes for the CT125, but they are not there yet, so working with the options that are available at the moment.

The only wildcards are the TB, the injector size and how to connect to the stock intake. Just curious what yall run for larger throttle bodies. I read 'thepen' mentioned he is running the Yuminashi 30mm unit, not sure what he had to modify to make it work. Also found the Takegawa 28mm for the CT, but have yet to find one in stock anywhere. I have the ADV150 injector, but the Koso kit calls for a 160cc injector so I have one of those coming now.

 

[m in sc]

On my grom with a 170/4v i ran a 34mm tb, could have gone to a 36 but i could also just tap 100mph with it w the 34.. . Yes, im serious. the injector i ran , if i remember, was what was commonly referred to as a '10 hole' unit. as far as the efi thing, run the aracer unit when going that far. exhaust plays into it as well, i made a huge exhaust for mine and it ran really really well till i grenaded the rod. and yes, the TBs are very different. I think you can get a standaone map sensor for the trail, but not 100% sure.

 

[dj423]

Ok cool, thanks for confirming. Yeah this is a bit overkill for my needs, but it's what I had. Long story, but I had picked up a well used OG grom when I lived in CA. Got all excited and started buying parts to redo the oil starved stock motor in it. Only to find out the bike was stolen . So rather than return the parts I just hung onto them hoping to someday get another Grom, but that never panned out. Ended up buying a 2017 KTM Duke 390 at the time. Once I saw the CT125 I fell in love. So here I am lol

I didn't mention, but the exhaust is the AR aodonly "stock look" pipe, with an O2 sensor bung welded in. Nothing fancy, but should work for this setup. After reading about many a melted pistons, I knew a wideband sensor would be a must if I was going to tweak anything on this bike.

 

[m in sc]

yup. i get it. you should be ok but like said, be careful. Im also excited if CJR finally figures this stupid ecm out.

 

[dj423]

I could be wrong, but it looks like the TB's for the Z125/ADV150 look very similar, with variations in the sensor part numbers. It uses a MAP sensor at least. So I ordered a cheap 32mm TB (for PCX150) from aliexpress to do a little R&D on and see if this is an option. At least the sensor block and IACV seem to be similar. If I learn anything of value I will share my findings.

 

[m in sc]

interesting, may very well work indeed.

 

[dj423]

A little deeper down the rabbit hole, using a MAP sensor, the CT125 would appear to use a speed density strategy for fuel metering and spark, whereas the Grom's are more of an alpha-N strategy (no MAP). So I can see why they used vastly different algorithms in the ECU code.

For grins and giggles, here is a bit closer look at the 16060-K35-V01 "sensor unit" that is unique to the Cub/CT125/PCX/ADV150 (semi-auto) bikes, and appear to all use the same part number so far post 2014+. This sensor unit contains the MAP, TPS and IAT in one unit. One thing that varies it seems, is the larger the TB, the vacuum signal port in the TB shifts location a bit that feeds the MAP sensor port on the sensor unit. Other than that, everything seems to be consistent.

 

[dj423]

Update: Looks like a slight mismatch on the scooter style TB bolt spacing from the Koso manifold to the Z125/ADV150 TB.

Manifold: 71.62mm spacing (33.8mm bore)
32mm ADV150 TB: 64mm spacing (32mm bore)

From what I have read a Grom TB has the bolt spacing about 64mm, so not sure if the Koso intake has a different bolt spacing just yet. I have a question into Koso support to confirm what I am looking at. So the ADV150 TB is mighty close, but not a "bolt on" option when running the Koso intake manifold.

 

[m in sc]

can you slot the holes? everything else lines up?

 

[dj423]

Yep that's one option. There are a couple areas of the manifold flange that interfere with mating up to the TB, near the top where the IACV mounts, and on the TPS side - but a little trimming with a die grinder would fix that quick. Could also tig weld the mounting holes in the manifold and redrill/tap to line up with the TB, so definitely doable.

 

[m in sc]

there you go. maybe a small adapter plate . sounds like you have the skills set to figure this out pretty easily.

 

[dj423]

Gives you a rough idea how far off the holes are, pretty minor difference. For "proof of concept", I may just slot the holes, in the TB since it was cheap lol

 

[Es89]

What about a 32mm throttle body with a 143 kit and Efie? Too much throttle body?

 

[dj423]

I would think with the right size injector it would run fine, to be sure it would be a really good idea to use a wideband O2 sensor with an AFR gauge to make sure it doesn't fall into a lean area under load. So maybe start with the PCX injector and work up if needed, or tweak the efie to add more fuel to keep it in a safe AFR. With a larger TB the engine will see more air volume so the stock fuel map may not be able to keep up at higher RPM and max out the duty cycle of the stock injector.