HONDA CT125 Big Bore Kit

[Samg7]

Cool video
Did you break this piston in the same way as the others?
I saw you rippin it in your video and didn’t know if that was right after the rebuild or not.

Eithjer way, I think it takes the ECM quite some time to fully adapt to modifications

 

[QuantiQualification]

I broke in this last piston faster than the others. The video you saw with the bike on the highway was after around 150 miles or so. The other three pistons that failed followed a very long and gentle break-in process. Nevertheless, I am certain the bike had time to fully adapt.

 

[Samg7]

Nice

Are you still on the 181 fuel map?

 

[m in sc]

looks like you got it. nice.

yes those wristpin c clips can be a bitch. lol.

 

[SLO]

watched the whole video. here's what i think happened. i think they were gapped too far, and you were getting blow by, and then pumped allt he oil out of the motor. i would guess the exhaust pipe was oily. i think the cyl is actually ok. you can get a ball hone and clean it up. make sure you clean it with brake cleaner.

bottom end is probably just fine. but yes, rise it out. mineral spirits are good for that.

the melted section at the top on the intake side is interesting. its def melted. But, it doesn't look to be a lean blow up. If you look under the piston dome, a lean blowup will show a bright white or ashy color to the aluminum, that's from heat at the dome that can be caused by lean or detonation. the tiny bit i could see looked dark, so that's good. pretty sure it got hot due to lack of oil and blowby, expanded, and caused the seizure. where are your afrs sitting? they need to be int he 13~13.5 range, 12~12.5 at wot.

as many motors and pistons as i have killed over the past 3 decades, that leads me to beleive thats what you are dealing with. Ive blown up lots of 2 strokes due to timing, and air leak lean conditions, IMHO, thats not it.

I would think you can hone the cyl, get a new piston and rings, probably a new small end bearing, and put it back together. put at least 50-60 miles on it before going wot.

as far as the piston hitting the plug, i'm running a slightly shorter plug in mine. its an old grom one i had, lower heat range but its shorter, don't have the number handy but i can get it.

.02

I am not sure that there are not counterfeit plugs being sold. If the piston hits the plug,try a different one,same brand,different source. Try it. I would swear this has happened to me,and after swapping,no issues. ??? Not relevant to this case perhaps,but I could only derive this conclusion,since thousands of miles since it happened. I was worried at first!

 

[m in sc]

they make different tip projection lengths. this matters when using an aftermarket piston.
i run CR9E plugs, they will clear anything .

 

[QuantiQualification]

they make different tip projection lengths. this matters when using an aftermarket piston.
i run CR9E plugs, they will clear anything .

I think you nailed it. I put the original Honda spark plug in thinking the one that came with the Takegawa kit was part of the problem. The Honda plug is probably longer than the one supplied in the kit. Put this in at the very end.

 

[QuantiQualification]

Nice

Are you still on the 181 fuel map?

Yes. I am experimenting with leaning it out a bit in some areas (dangerously I might add since I don't have an afr meter). The map is a little scary for the 181 after studying it. There is a pretty big dip in fueling at 8000 rpm. Seems like a bad place to have a dip when going to 164cc the location of dips might change up or down some. I will post a 3D of the map.

 

[QuantiQualification]

 

[JPMcGraw]

Before i installed the 143 i played around with the dips in the 125 maps. If you run the unchanged Takegawa map, let it learn, then change some of the huge negative dips to 0, let it learn again, you will notice the bike hitting mud and bogging down until its out of that rpm column and back to the unchanged section of the map. I don't have a wideband installed but my butt and ears could tell it was running rich so i wouldn't be too concerned. Flow be cray sometimes.

I think the 125 MAP with exhaust, cam, filter has -1000 or -1500 dips and those are what i played with

 

[m in sc]

I agree, you can usually tell by feel for the most part... if you know what to feel for.

afrs are the best option, but even if you run an egt or a cyl head temp gauge (like one that goes under the spark plug) you'll know some comparative real world data that can be reviewed to make an educated guess/plan.

 

[QuantiQualification]

@JPMcGraw I would love to learn more about what all you have installed engine wise and what specific map you are using. Did you install a bigger injector?

 

[JPMcGraw]

Yuminashi 143
Takegawa Fi-Con
Takegawa Cam (N-15)
Finbro Super Head 3.0
PCX 150 Injector
Yoshimura GP-Magnum
Takegawa Pod Filter
Takegawa 143 (Intake + Exhaust + CAM) fuel MAP
CPR7E9 Plug

I had the Takegawa 143. I took a long 45-50mph ride solo and later a slower neighborhood ride with a passenger and the clacking sound started to show itself. I tightened the valves, let it idle, and it still didn't sound normal. I had 350ish miles on the Takegawa 143, and no problems other than the noise. I decided to go ahead and cut out the anxiety and swap it out.

Intake side

Exhaust side

Top

Cylinder wall


It doesn't look too too bad. The cylinder wall doesn't have any damage at all that i can see or feel with my fingernail. The piston looks like it has more wear on the intake side compared to the exhaust. The clacking sound that i had with the Takegawa is gone now but it also only has 25 miles on it.

After putting in both kits the Yuminashi C-clips are WAY less aggravating so that right there should be enough to sway everyone.

 

[QuantiQualification]

Thinking I don’t fully understand the Takegawa FI Con E fuel controller. I think it is basically a dilts enigma V with some maps preloaded on it. Does this thing just control and force Open Loop all the time? In other words no O2 signal is used whatsoever? Here is a description from Webike for the Dilts.

"3. O2 Feedback Stop

The CT125 (JA55) has a large feedback correction area by the O2 sensor, and even if the fuel is increased or decreased by the sub-computer, it will be returned to its original state by the feedback correction within this area.

The newly developed feedback stop function in type-V stops the O2 feedback function (closed loop) without going into error mode (FI lamp on).

This eliminates the need for feedback fuel correction and eliminates the need for O2 sensor correction for fuel increase/decrease at all engine speeds and accelerator openings, allowing the ENIGMA to provide the correct fuel setting at all engine speeds without correction for fuel increase/decrease.

For the CT125 (JA55), which has a wide feedback area, this is especially effective for a wide range of fuel settings.

In the CT125 (JA55), the ECU monitors the feedback status, so if you use a conventional sub-computer to increase/decrease the amount of fuel, the ECU will detect the increase/decrease and the FI warning lamp will light up and it will go into error mode.

The type-V uses a unique technology to stop the feedback so it will never go into error mode (FI lamp on).

The FI lamp will only light up when there is a real trouble, and it will let you know that your important bike is out of order.



CT125 Power Graph at 50% Accelerator Opening (O2 Feedback Area)

This is a reproduction of the condition when riding well in the city at 50km/h-70km/h.

In such a frequently used O2 feedback area, the ECU narrows down the fuel to the economic AFR, so the power/torque output is also reduced as shown in the graph (blue).

Just by installing the ENIGMA Type V, the O2 feedback will be stopped and the area will be corrected to the A/F ratio where the power comes from, so as shown in the graph (green), the power output in the area that is often used in town will be improved and the accelerator response will also be improved.

*We just installed the ENIGMA. No fuel tuning is done in this test"

 

[QuantiQualification]

I just rode the bike with the O2 sensor completely disconnected. No warning lights, no change in performance whatsoever. Looks like the Takegawa fuel controller simply does not use the sensor at all and lies to the ecu that there is a sensor. So the fueling that is used, does not vary or change at all. This is bad but has some okayish points. I guess the original O2 sensor location is free to throw a wideband in then. Any thoughts?

 

[JPMcGraw]

I got a 14point7 LSU 4.9 wideband and the O2 -> Wideband adapter so i might hook all that up this weekend and see what happens.

That would be awesome if the learning time i give it when i mess with the map is unnecessary.

 

[m in sc]

yup.
open loop all the time? that sucks IMHO. no way to add an autotune? I still believe the biggest drawback of the trail ecm/power is the timing curve. 'the pen' and i discussed this quite a bit when he was doing his conversion. the stock ecm works in closed loop all the time, or is capable thereof., albeing w a narrow band. IMHO< i really thing mechanically advancing the timing (offset keyway, moving the pickup, etc) and then adding a programmable timing controller in conjunction w a fueling adder (like the efie i use) would yield a lot of the same ecm results.

I -wish- dynojet would do a power commander for this ecm. But i wouldn't hold my breath.

 

[RustyRodder]

Dumb question time- would a megasquirt setup work on these?

 

[m in sc]

ive seen them used on OG groms.

 

[squeaks]

I was wondering if any one has checked the piston to cylinder fit? I bought the takagawa 143 kit, but after seeing so many issues with them
I never installed it, but i did experiment with the piston and liner by putting them in the oven to 200 deg.
at that temp the piston is solid in the cylinder. also even cold a .002 feeler gauge would not clear.
I used a small hone to work that cylinder like i used to do with the air cooled diesels I used to build until I got a good fit @ the 200 temp.
I have not tried it, and seeing all this stuff with the fueling don't think I will now sounds like maybe the old carbs may be better, just install a bigger jet for 20 cents... ?