HONDA CT125 Big Bore Kit

[QuantiQualification]

I finished installing the kit yesterday and completed two 20 mile test loops at 35 mph and 40 mph respectively. So far so good. Will complete successive loops at 5 mph increases as I break the new components in.

 

[QuantiQualification]

Elevation that I am running at is 846 feet.

 

[QuantiQualification]

20 Mile Loops at 45, 50, 55, & 60 mph completed with full success with full winter riding gear including a huge military parka with billowing hood all in a upright position. 65 mph loop was not possible in the upright position with speeds up to a maximum of 62 but average of about 60. 67 mph observed with a bit of a tuck. I will pull the Takegawa air filter off and try the stock air box next for a top speed loop for comparison. Overall, extremely pleased with the upgraded performance with the max possible speed upright, prior to the kit, was 52 mph and with full tuck, 60. So, plus 8 mph and plus 7 mph respectively.

 

[QuantiQualification]

The Takegawa Air Filter does in fact improve the speed. 60-61 mph average with it, 57-58 mph with the stock box, so quite significant. I did 1st run with, 2nd run stock, 3rd run with so pretty much verified. Full tuck has allowed me to touch 70 mph on that 3rd run so M IN SC is spot on. On a separate note, the 143 has started to make some ticking/clacking noise. Pretty sure it is not valve clearance but I will check them again. M IN SC mentioned some noise on a Takegawa 143 install that he did. Wonder if I am getting piston slap?

 

[QuantiQualification]

Valve clearance is good. Clacking still present - seemingly originating from the cylinder/piston section.

 

[m in sc]

mine ate a piston... i hate to tell you that. actually 2x, thats why i went to the yuminashi one, they had the oiling holes under the ring land on the piston face, where the takegawa didn't. . counter intuitive brand wise, i know, but i absolutely happened to me 2x, and ive been building motors for 35 years so I'm fairly proficient, and these aren't difficult to build, at all.

the takegawa air filter, is it the one in the stock airbox foam one, right?

 

[QuantiQualification]

The air filter is actually a stand alone unit that connects directly to the throttle body. In my case the Takegawa big throttle body.

Could you describe the sound that piston made as it was being gobbled up? Did it destroy the cylinder as well?

Mine clacks at idle and continues to do so in time with the rpm almost sounding like a buzz at high rpm while riding.

 

[m in sc]

has a rocker/valve tapping sound but as you said, sort of indiscriminate 'central' location. you can use a stethoscope (or a dowel to the ear) and you'll hear it midway down the cylinder.

the cyl was relatively ok. what I did was, i figured the original one was just an outlier, so i ordered a spare, and sent the other one back as defective. takegawa said it was not for our model.. which is bullshit, because they said it was for the Japanese only model CT125. the cyls are the same across all of them, all the way back to the 1st gen groms. 22 and later groms/monekeys I 'think' are different though. I know they are the same before 22, because prior to this i had a high compression 125 piston/cyl on it that was leftover from my '14 grom. (still have that setup saved, and the stock unmolested trail cyl/piston and a blown up takegawa 143 cyl/piston on hand)

However, webike agreed with me and refunded the 1st one saying it was indeed defective. . when the second one went i just gave up and ordered a yuminashi cyl/piston, haven't had an issue since. as in, a few thousand miles. never tried to get a refund ont he second setup. as a sidenote, i changed nothing else between the 3 cyl sets in regards to tuning or intake exhaust at the time. the one thing i changed was the cyl/piston which proved my point to me.

I don't feel as you did anything wrong, at all. But i'd almost bet your piston skirt collapsed a bit and that's what you are hearing. i guess you could always go with a different piston and get your cyl honed to work with it.

 

[Samg7]

The Takegawa Air Filter does in fact improve the speed. 60-61 mph average with it, 57-58 mph with the stock box, so quite significant. I did 1st run with, 2nd run stock, 3rd run with so pretty much verified. Full tuck has allowed me to touch 70 mph on that 3rd run so M IN SC is spot on. On a separate note, the 143 has started to make some ticking/clacking noise. Pretty sure it is not valve clearance but I will check them again. M IN SC mentioned some noise on a Takegawa 143 install that he did. Wonder if I am getting piston slap?

Can you post a picture of the air filter setup you're running?

I wonder if that ticking noise is present from cold start, or just when things warm up?

 

[QuantiQualification]

The air filter setup is Takegawa part 03-01-0035. Pictures attached.

The noise is present at cold start up and continues when warm.

 

[QuantiQualification]

And . . . Here is my first YouTube video ever, for your entertainment!

Please subscribe @ https://www.youtube.com/@QuantiQualification?sub_confirmation=1

 

[Samg7]

@x29Saab I remember another member temporarily ran an air filter similar to yours and it did not go well. They were running a stock cylinder/piston I think.

Yes, I ended up experimenting a bit and decided to just throw a pod filter straight onto the throttle body, Do not try that, I wouldn't mod anything with the air intake system unless you have strict control over your AFR's. I went on a ride with that pod filter and ended up swelling/scoring the piston up. Stock Ecu couldn't correct the Afr for the pod filter.

Although you do have the fuel controller so the situation is a little bit different…

Take the cylinder off and see what she looks like.

 

[m in sc]

sure sounds like piston slap to me. dammit that suuuuuucks.

 

[QuantiQualification]

@x29Saab I remember another member temporarily ran an air filter similar to yours and it did not go well. They were running a stock cylinder/piston I think.



Although you do have the fuel controller so the situation is a little bit different…

Take the cylinder off and see what she looks like.

Yes, will be disassembling it this week to see what is happening on the inside.

 

[QuantiQualification]

sure sounds like piston slap to me. dammit that suuuuuucks.

Will know soon enough. Went to the Yuminashi website to order a 143cc replacement kit but got tempted by the 164cc instead! Should be incoming shortly. Planning on trying that kit with the stock air box on the 181cc fuel controller setting. Should be interesting. Can't believe how inexpensive the Yuminashi kits are.

 

[RustyRodder]

Random thought- can the people who write tunes for these bikes use the takegawa/kitaco/dilts controllers to upload tuning files since the ecus are less than accessible?

 

[QuantiQualification]

I can edit the values for added or subtracted fuel from stock for different rpms and throttle positions.

 

[QuantiQualification]

Here are a couple of maps.

 

[m in sc]

i had a 164 on my grom w a big valve head, it was a very good kit. ran it for a few yrs before i went 170 4v. had to run a Power commander and autotune on that one, but it was a solid unit. would recommend the high volume oil pump if not already on. .02

 

[QuantiQualification]

Here is a map I made using an interpolation (and guessing) from three of the other maps that are built in for the Trail. This one will use the little pod filter from Takegawa and 164cc Yuminashi Cylinder and all the other Takegawa kit I put on.