HONDA CT125 Big Bore Kit

[m in sc]

fwiw ive had zero blow by on mine, have over 1500 miles on the big bore w cam and exhaust. but im still running stock gearing, no point in changing it for me as i can maintain speed up hills, 50+. .02

 

[SLO]

Good to know, thank you! How many miles have you put on it? And what exhaust did you use? I am looking at the MiniMoto exhaust

I put a Mini Moto stainless exhaust I got from Japan for about 300 bucks delivered. I also removed end cap,saved for later if needed. Also punched out baffles I noticed after looking into the exhaust pipe. I drilled ,then pulled out with long needle nose pliers. It is quiet ,until you open up the throttle all the way. Better than reaching for the horn,if you need to let someone know you are there.Less annoying way to do it also. I have about 560 miles on big bore install,and I think around 4600 on bike.

 

[RustyRodder]

Looks like another Controller came out. Going to translate the manual a bit and see what it says. Cheaper than the Takegawa, but still pricey. But, capable of custom tunes- maybe this means the US market will have them soon?

https://www.kitaco.co.jp/goods_detail_en/P763-1470200

 

[m in sc]

233 bucks is cheap for a fuel controller. imaps have been around a while, never heard much good about them.. but? has to be better than nothing i would guess. however.. as I've said.. the timing map is the biggest issue after getting the fueling right, and that doesn't address it. but for the cost its worth a shot

 

[RustyRodder]

233 bucks is cheap for a fuel controller. imaps have been around a while, never heard much good about them.. but? has to be better than nothing i would guess. however.. as I've said.. the timing map is the biggest issue after getting the fueling right, and that doesn't address it. but for the cost its worth a shot

Looking at what it does, seems like it's basically an Efie? With maybe a bit more adjustability. Attaching the translated instructions for any curious minds.

 

[m in sc]

it kind of reminds me of a thunderbox for harleys. that being said, keep in mind 2 ecus were used for the trail, and asia used the older version .. like a 1st gen grom, whereas in the us it was the newer version which there is little support for. the reason i mention this is im not sure how the interface will work.

the upside of the newer ecm is it will adjust across the whole range.. at the pre determined afr, which is lean. hence the eife i used working.. because its lying to the ecm. the imap as you said, basically does the same thing, but is also using tps and engine temp... (but i would take that with a grain of salt) as an input, which would be better. if there is an option to run x amount of time to warm up int he settings vs using engine temp, i would consider using that instead.

 

[Samg7]

Does any run a bigger oil pump when running a 143 BBK?

 

[Thepen]

Does any run a bigger oil pump when running a 143 BBK?

They say its recommended, I slapped it on since its so cheap anyways.

 

[m in sc]

I'll be honest, i havent as of yet, but will eventually. .

 

[Konik]

Is there a vid of a kit being put on the trail? I've seen monkey one and one of the guys has a post video afterwards but not where its being installed. Added accessories to mine but this would be something different. Thinking of putting on a Yuminashi 143 or even the full kit with fuel controller.

 

[Samg7]

They say its recommended, I slapped it on since its so cheap anyways.

Did you go with this yuminashi?

YUMINASHI 36.8% UP HYPER OIL PUMP (MSX/GROM/Z125 MONKEY/SUPER CUB 125/...)

YUMINASHI 36.8% UP HYPER OIL PUMP (MSX/GROM/Z125 MONKEY/SUPER CUB 125/...) (15100-KPH-YF3W)

www.yuminashi.eu

 

[SLO]

Does any run a bigger oil pump when running a 143 BBK?

Yumiashi claims not needed. They do recommend 20w-50 synthetic. I have a 238 cam with mine,opened exhaust,intake,and a 150 injector.Run a 13 tooth sprocket in front as I live in mountains.

 

[Samg7]

Yumiashi claims not needed. They do recommend 20w-50 synthetic. I have a 238 cam with mine,opened exhaust,intake,and a 150 injector.Run a 13 tooth sprocket in front as I live in mountains.

How is that setup? I’m assuming you have the 143 as well. No fuel control?

 

[JPMcGraw]

Is there a vid of a kit being put on the trail? I've seen monkey one and one of the guys has a post video afterwards but not where its being installed. Added accessories to mine but this would be something different. Thinking of putting on a Yuminashi 143 or even the full kit with fuel controller.

When i put on my BBK i just watched a few monkey and grom BBK install videos. Step by step it was pretty straight forward

 

[m in sc]

its easy TBH if you have any mechanical skill. I have the same kit, its been doing well. the worst part overall is getting the cyl over the rings on the piston, and getting the piston circlip in w/out launching it or dropping it in the cases (if you haven't ever done this before). IF you are going to mod it with a fuel controller that can adjust the timing curve & get the motor rpms up higher than the stock redline..., then the bigger oil pump become a necessity. But with a stock ecm, the stock pump is fine. I'll change mine out whenever i pull the clutch cover just because i'll be right there and it so cheap to do... but it hasn't had any oiling issues.

 

[SLO]

How is that setup? I’m assuming you have the 143 as well. No fuel control?

Yes,143cc big bore kit from Yuminashi. Go to Yuminashi Direct sales. No fuel controller needed. They do specify that you upgrade the injector. I put a 150 Honda injector in mine,and I wonder if it was mislabeled.It ran rich for the most of the 4000 plus miles,until I changed the plug per their specifications. NGK #6 vs # 7. NGK plugs lower the number ,the hotter they are,it is the opposite with some others. Nothing like a stock bike. It is a motorcycle now! I have around six hundred miles on install,and the only problem was when I installed the cam,I did not line up the cam chain sprocket tab with the cam,and it broke after about 20 miles.My fault,should have loosened the tension on chain,or quit for the day,and finished the next day after resting.

 

[Samg7]

Yes,143cc big bore kit from Yuminashi.

Thanks for the info!

Right now I have a 143 setup from my friend Eddie, you may know him as @Lazy Dog Productions on this forum, great guy. The original post in the thread was about him. He has a great YouTube channel btw.

Anyway, last time we rode he set me up with that 143 kit. So I have the PCX150 injector as well. I haven’t had time to install it, but I’m back in Thailand at the moment and will meet up with Eddie again soon, this time he’s gonna set me up with a cam + ported head as well as an tuned ECU from a Honda Wave. I have seen something about the North American CT125’s having a different ECU to the Asian CT125’s… so I am still curious about this part.

I’m not sure exactly which cam he is running, it may be that Yuminashi 238.

Since I’m in Thailand I thought about dropping by Yuminashi and getting their 143 kit to compare, along with the 238 cam if the cam Eddie has for me is different.

 

[Samg7]

It ran rich for the most of the 4000 plus miles,until I changed the plug per their specifications. NGK #6 vs # 7.

The bike was running rich until you put in the NGK #6, is that correct?

 

[m in sc]

yes, the us ecms are different than the thai ones.

 

[ShieldArc]

yes, the us ecms are different than the thai ones.

Why and in what way?