HONDA CT125 Big Bore Kit

[m in sc]

a long runner @ the bellmouth will always give better flow (more laminar) than an open pod as long as its sized right, just fyi. hence why i went the way i did. since you have a 164, you should be fine to hit your goals i would imagine, even w the pod filter. but its going to take at least 50 miles ot be safe to really get any serious throttle on, takes time for the ecm to learn. My experience is to do very short wot blasts, like really short, so the ecm learns to throw more fuel at it so its at least safe during the learning process. the power commanders do the same thing, but learn a lot faster, same with holley sniper systems, etc. just my .02.

 

[QuantiQualification]

Finally threw on an EFIE from Eagle Research. We will see how it does!

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[m in sc]

good video. just remember everyone else, it needs to be wired in backwards (in regards to the white and green wire) from what they say in the instructions to get it to run richer, not leaner.

green to the ecm, white to the 02 sensor.

 

[QuantiQualification]

good video. just remember everyone else, it needs to be wired in backwards (in regards to the white and green wire) from what they say in the instructions to get it to run richer, not leaner.

green to the ecm, white to the 02 sensor.

Excellent point. I will leave a note in the description to emphasize this.

 

[RustyRodder]

Finally threw on an EFIE from Eagle Research. We will see how it does!

That is a great video!

 

[QuantiQualification]

That is a great video!

Thanks! Here is a quick update with the Kitaco 164cc kit installed.

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[Samg7]

Are we all pretty set on the 250mv for the EFIE?

 

[m in sc]

its definitely safe. ive run settings between 20 and 27. 25 does seem the sweet spot, which corresponds to what the grom guys always found. i think mines at 25 or 26 right now, and has been for well over 1000 miles, prob closer to 1500.

 

[Samg7]

Am I correct that the lower the number, the closer to stock? In other words, 300mV is richer than 100mV

 

[m in sc]

yes. exactly.

 

[QuantiQualification]

I second @m in sc . Where mine is centering during closed loop seems pretty ideal at 250mV. Still a bit rich but still perfectly in the top power band. Get much richer and power drops a bit.

 

[Samg7]

Gracias amijos

@x29Saab you mentioned '... during closed loop ...'.

It was my impression that the Grom ECM operates in closed loop up to a certain RPM range, then switches to open loop extrapolated from the closed loop conditons.

However the CT125 differs as it operates exclusively in closed loop.

Does the CT125 ECM ever run in open loop?

 

[Samg7]

I second @m in sc . Where mine is centering during closed loop seems pretty ideal at 250mV.

I wonder if 164cc @ 250mV would be similar to ~230 @ 143

Would be cool to have 'different maps' for normal/eco mode.

Like 100mV for eco and 250mV for normal.

 

[QuantiQualification]

Gracias amijos

@x29Saab you mentioned '... during closed loop ...'.

It was my impression that the Grom ECM operates in closed loop up to a certain RPM range, then switches to open loop extrapolated from the closed loop conditons.

However the CT125 differs as it operates exclusively in closed loop.

Does the CT125 ECM ever run in open loop?

Here are actual results from the narrowband O2 sensor for different fuel injectors with the EFIE set at 250mV. Seems to suggest an open loop section at WOT. In theory, all the injectors should behave somewhat similarly if the open loop changes with closed loop numbers. I see quite a bit of dissimilarity so interpret how you see it. Nevertheless, the behavior is now somewhat documented. It would be awesome if someone did the same test with a Wideband O2.

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[QuantiQualification]

Here is the latest and final build video.

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[Samg7]

Just skimmed the injector video.

Shouldnt we only be concerned with teh results at WOT?

I would think many of those injectors would have been OK since the EFIE is at 250mV...

Also, my stock bike with a Takegawa exhaust could hit 55 GPS. The bike with the PCX150 injector and the 238 cam can hit 57 on flat, and solid 45 average going up the canyon.
I wonder if that's an elevation thing.

 

[QuantiQualification]

Just skimmed the injector video.

Shouldnt we only be concerned with teh results at WOT?

I would think many of those injectors would have been OK since the EFIE is at 250mV...

Also, my stock bike with a Takegawa exhaust could hit 55 GPS. The bike with the PCX150 injector and the 238 cam can hit 57 on flat, and solid 45 average going up the canyon.
I wonder if that's an elevation thing.

I think you need to pay attention to the transition as well as WOT (WOT is absolutely the most critical). The transition running lean, even for a few seconds, adds to the total heat that needs to be rejected by the engine. Heat added / Heat dissipated over time and all that. Understand you on the speed. The bike with the stock air box is limited, for the most part, but it will hold near to the top speed regardless of hills and wind with the 190cc injector. I ran it up a pretty steep hill into the wind, and it just tractored up it at 55-56 mph. Just peg the throttle and go, like a cruise control. That is really what I set out to achieve. The power curve drops like a rock after a certain speed. With the Takegawa air pod, some of this restriction is alleviated. Ask @m in sc about intake runners etc. to really get the most out of this little engine. I am very pleased, however, with the ability of the EFIE plus the correct choice of Fuel Injector to pretty much get you what you need out of this bike. I don't think you really need an autotune unless you need the nth out of it.

 

[m in sc]

keep in mind, the top speed is rpm related. the timing curve on the ecm isnt changed, and it will not really rev more, but will make more power up top when its a bit richer than stock. the ct125 ecm is in closed loop all the time, whereas the grom ecm, at least the old ones, have a closed and open loop segments. with larger bores, like my 143 or his 164, the gain is within this range, and can hold power better up top, more torque up to peak w more fuel (13 is afr vs the stock 15~14.5 target), and cooling to avoid a blow up.
read 'thepens' post on his big bore with full ecm tune, and hes in the 70-75 mph range, and yes, most of that was due to changing the timing curve. + the fueling up top to handle it.

i have speculated moving the pickup to 2-3 more degrees advanced will allow more rpm and therefore more top end, i just haven't tried it yet.

 

[Samg7]

Anyone got the spec for the yuminashi 143 ring gap?

 

[JPMcGraw]

I couldn't find the exact gap so i consulted google for general ring gap formulas. When i installed the kit and checked the rings they didn't need any grinding.

Still double check but you should be good to go.