More Speed for the Honda Trail 125! - Big Bore Part 1

More speed takes more power, so we install a Yuminashi big bore kit on our Honda CT125.

0:00 Intro
1:32 Teardown
4:29 Checking Ring Gap
5:43 Piston Assembly
6:40 Engine Reassembly
10:29 Fuel Injector
11:08 Buttoning Up
12:00 Wideband 02 Sensor
15:13 First Start
16:15 Road Test

#ct125 #trail125 #hondamotorcycles

[erniesautowerks]

I watched the whole damn video….and I don’t have any intention of owning a Trail 125 much less modding one. Very soothing voice and detailed easy to understand explanations. 👍👍

[zrx]

Great video, as a kid I worked on these single cylinder Honda’s. They sure take a beating, great camera work. 🤓

[volt]

When my 50cc 2 stroke died, my dad bored it out to 80cc and a new piston. Before it would cruise at 45mph but after the rebore would cruise at 60. It started a trend for my mates😂

[JshDav]

Looking forward to seeing your approach to tuning this thing

[beachthor]

Dude this was excellent. I appreciate the info about what can happen when things aren’t as they should be ie piston ring gaps causing seizing. Provides a lot more context for me as a hobby mechanic

[sierrafoxtrotgolf]

Great video even if it didn’t end up quite the way you wanted.

[avdeluxe]

Great video! I used to have a 1975 Honda XR 75 and had to replace the timing chain. The process here was a bit more complicated but overall very similar process. On the XR 75 the engine had to be removed and crankcase needed to be split to get new timing chain on. I have a 2024 CT 125A now and currently dont plan on modifying it. ❤

[peter]

What a lovely little engine to work on. That's another advantage of choosing a smaller machine, as well as great economy and just the lower weight when you need to push around or manhandle. I had a 90, super little sporty model (SS90, 90SS?) in the 70s and it was the most fun bike I've ever owned. Great video, thanks for posting.

[miketirta]

Great video. Really helpful and visually detailed. I probably will do this on my 2021 Trail125 by this summer.
And thank you for showing the wideband sensor result, because of that, I changed the fuel injector order from 170 down to pcx155 on my Yuminashi's shopping list.
I hope it will make my Trail run less richer. What do you think?

[zoby]

👏🏼 👏🏼 👏🏼 dude, appreciate the detail. Thanks for sharing!

[Mahi-trblx]

Finally the mail’s gonna be delivered on time

[KtotheL]

very nice video and well done ! thanks !!

[zefautino]

Very rare to find an interesting video these days. Don't know how people can be so boring and think they are the greatest.
Don't know why I'm watching this video, as this is something I did more than once, a sign i enjoyed the video.
You're absolutely right about going higher on cc brings more issues. I installed a 181, and guess what? Installed the original 125cc back and never again had another issue with it. Kept the piggyback ecu for the high RPM camshaft though.
By the looks of it, you're also having problems with yours. I took mine to the dyno, 13hp. And I still brought it back to original cc due to the constant issues. The worst of all was stock bikes not only keeping up with mine, but also overtaking me. That was not funny.

[waimeaguyz]

The installation appeared straightforward until it came to filing the rings, which I wouldn't be capable of handling. I assumed it would be a simple install-and-ride process. Moreover, riding at high speeds, such as 60 mph, on a small bike seems perilous without larger tires. I appreciate the power for hill climbing, similar to the CT110 that featured a sub-transmission, allowing it to traverse any terrain.

[bw]

The ct125 dosent need something to make it go faster, it goes at the correct speed to see life and beauty and humanity unfold in an enjoyable way. The problem is the worlds going to fast and it’s everybody’s job to recognize this and slow it down. The ct125 is a tool to help you recognize this and recalibrate your life. Don’t screw the tool up by making it fit in with the broken world.

[pdc]

Excellent video, thank you very much!

[Troysbuildsnlife]

Oh wow, someone in YouTube Bike Land actually does the oil ring pack in the right order. Thats a first...

[guidosamson]

I hate fuel injection. I love the carb

[Vadderax]

I find this interesting, i would have changed the gear ratio before the engine for going on the road, it also defeats why they call it a trail 125 bike. If anything i would have shorten the bikes gear ratio for acceration and torque by the rear aftermarket sproket to just to closly match the 1977 honda ct 125 trail bike with a 53 teath rear sproket for trails, back roads, and neighborhood riding to grocery stores. But i also know everyone has there own purpose for it.

I know this because find parts parts for the '77 is like fishing for needles in hay stacks. I had to learn every inch of my grandfathers bike to fix it. its got a top speed of 30 mph, it was imported by japan only in '77 to america. And it was mostly bought by the goverment / forest service and advertised to the public for a farm bike.

[billwatcher]

Big bore kit is a good way to go. Just need a little adjustment in the fuel mixture. The bigger cam is a bad idea. With that cam your going to loose all of the increased torque the big bore kit gives you. A big cam is fine for a street bike. On a trail bike big cams suck.