HONDA CT125 Big Bore Kit

[QuantiQualification]

Piston problems?

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[m in sc]

dammit, knew it. IF you bought it from webike, ask for a refund. they did it for me. not the 1st one

takagawa needs to fix that shit in their design.

 

[JPMcGraw]

Man that's some bull spit. Mine doesn't make the noise when its cold or warm but i think im still going to go ahead and get a backup ready

 

[m in sc]

IMHO, if you drill 3-4 1.5~2mm holes about 5 mm under the ring oil land in a straight line across evenly spaced, would be fine. not uncommon on some high perf 2 stroke pistons to aide in cooling/oiling. the yuminashi piston has these from the facotry, which is why i used it. .02

 

[QuantiQualification]

dammit, knew it. IF you bought it from webike, ask for a refund. they did it for me. not the 1st one

takagawa needs to fix that shit in their design.

I did buy the full hyper e kit from Webike. I will see if they are willing to send me a partial refund for just the piston and cylinder.

 

[SHEA]

I have been reading through this thread and I am a bit confused. I have a 2021 Honda Trail 125 US version. My performance mods; I just ordered a Yosh Pipe - a K-Speed Diablo V2 air filter cover and a - SP Takegawa Power Airfilter - from WeBike. Next, I wanted to order a Yuminashi 143cc BBK - Yuminashi S-238 Cam and a - 140CC B-type injector. Where I get confused on is thread is, will I need to get some sort of controller for the ECU with my proposed mods? If I have to get some sort of controller for the ecu for the mods to work right, what are the options? Options don't seem to be as plentiful as they are for the Grom/Monkey, which seems crazy to me?

 

[m in sc]

you are correct. like ive said, im running the efie, which fuels well but no timing control. very limited choices for ecm controls, whereas you can pick any flavor for the pre 22 grom.

the nice part is the trail ecm will adjust enough to fuel ok, and stay in closed loop... but keep it at 14.7. the efie setup i have is dialed in to where it runs at 13-13.5 ish.

 

[SHEA]

Thank you for the information. I am not versed on anything efie. So for me, plug and play is best. It seems doing engine mods for the CT (in my case for added torque) is like heading down the rabbit hole (no efie knowledge) - it all seems okay until I am to far in! I will likely stop at where I am with the pipe and airbox mods for now.

 

[m in sc]

its 4 wires. lol. super easy. you are just adding voltage from the 02 sensor to the signal to the ecm. so there's power, ground, input, output, and a set screw.

 

[QuantiQualification]

Man that's some bull spit. Mine doesn't make the noise when its cold or warm but i think im still going to go ahead and get a backup ready

So here is the proof in the noisy pudding. That Takegawa 143cc piston and cylinder was bad. New 164cc piston and cylinder from Yuminashi installed and the bike sounds normal again. Here's the Video.

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[ducatirdr]

I need a WIKI in the mods page that has a list of Stage 1, Stage 2 and etc with details on what to expect from these options. For instance. I want to bike to perform 5mph faster than it currently does. So 35mph up steep 8-13% grade could give me 40mph. A steady 45mph on moderate inclines would be 50mph. I'm not looking for 70mph. Just a bump up 5mph from where it is stock.

I'm not sure what it would take to give me that bump. Also I really like the stock exhaust and intake. I tend to ride in areas that are not 100% legit so stealth is a good thing. Water crossings are often found on those trails. Is this an impossible ask? I do other bikes for faster riding but I just want the safety the 5mph bump gives me on local New England secondary roads where 50mph is the make or break for safe access. I have a stock 2019 SuperCub and once it broke in it maintains a healthy 5mph everywhere.

 

[JPMcGraw]

i vote ducatirdr gets to organize and put together the wiki

 

[m in sc]

I rode mine yesterday, and hit a legit 65, on a slight downhill, but can maintain 55-58 pretty much everywhere, and 52-53 on steeper long hills.

my wife has a super cub and yes, they are faster. they also have the old style ecm.

I agree, 50 mph up a hill is def a good benchmark as a bare minimum.

 

[ducatirdr]

M in SC - Did adding the cam and the efie give you any additional mph on the same roads?

 

[m in sc]

well, those were the 1st 2 things i did. the big bore kit was def great for midrange power, as was the exhaust. The intake and 28mm throttle body helped up top, probably the most. (last 2 things i did).

I'll be honest, i might retard the cam a few degrees see it if it helps the top end. right now its 2 degrees advanced. even it you aren't going to play with cam timing, the adjustable cam gear is way, way stronger than the stock one, highly recommend and its cheap as dirt. It locates with an actual steel pin, not a stamped tab.

the -only- downside is you have to remove the 2 aluminum 'tabs' inside the cam cover to clear it, really easy to do though.

 

[QuantiQualification]

well, those were the 1st 2 things i did. the big bore kit was def great for midrange power, as was the exhaust. The intake and 28mm throttle body helped up top, probably the most. (last 2 things i did).

I'll be honest, i might retard the cam a few degrees see it if it helps the top end. right now its 2 degrees advanced. even it you aren't going to play with cam timing, the adjustable cam gear is way, way stronger than the stock one, highly recommend and its cheap as dirt. It locates with an actual steel pin, not a stamped tab.

the -only- downside is you have to remove the 2 aluminum 'tabs' inside the cam cover to clear it, really easy to do though.

M in SC, did you gap the piston rings before installing the Yuminashi kit? I gapped mine and am having some serious problems. Just wondering about causes . . .

 

[m in sc]

mine were in spec I checked them on install, were good to go. Yours too wide or narrow?

 

[QuantiQualification]

I thought they were too tight so I ground them until the gap measured properly. I think I ground off way too much on both the number 1 and number 2 rings. When I put the rings in the cylinder and brought them level, the ends were touching. I ground some off and they were still touching. I repeated multiple times until finally with a final grind it went from zero to in spec (at least theoretically). I think what was actually happening is the sides of ring were pushing in making contact with the ends but not all of the ring was in full contact with the bore. I also noticed that one of the rings was a little sticky in the piston groove when assembled. Didn't think much of either potential problem but needless to say, I had a major failure and total loss of all oil (probably consumed?). I will be putting up a video on what I see once I get it all disassembled. YIKES. Hope the bottom end and top end is still okay. Don't care about the piston and cylinder so much!

 

[m in sc]

wow. yea, ive done 3 yuminashi cyls overall, never had that issue with the rings. I had one, back in 15 eat a ringland, but that was a casting flaw in the piston, and they made it right.

 

[QuantiQualification]

Well here is the video. Let me know what you all think went wrong! Might take 30 minutes for the video to post.

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