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😂

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. 👍👍

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

Great illustrations of the upgrades

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

Looking forward to seeing your approach to tuning this thing

Excellent job Mate!

very nice video and well done ! thanks !!

Awesome video ❤

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

Excellent video, thank you very much!

That’s pretty awesome 👍

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

great video thanks

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?

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.

i just subscribed to you now i need to go back and watch your videos so i know what you did wrong and did to fix it. so i can do it right the first time. I HOPE. lol thanks i wish i had found your channel a couple months ago.

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.

The top record of the C70 engine is in the 87mm piston by a workshop in Yogyakarta, Indonesia

Surely a less restrictive exhaust system would be needed with a big bore, cam and bigger injector.

Hello how is the engine breaking with the new piston?

I look forward to the CBR300 swap 😅

I have a green mean stock machine 2023. In 1966 had a Honda Super 90. It was beaten up by the delta phy fraternity at Edison High school Fairfax county VA. I rebuilt it fought of the hate. If I had your video in the day... Really was a well presented video.😊

You can also use the o2 sensor like a probe and put it in the end of the tailpipe?

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.

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.

Needs a camshaft upgrade!!!!

Could you measure the OE ring gap and use that as a base line?

i might be wrong but why did the cylinder say 125cc on the big bore?

I hate fuel injection. I love the carb

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.

Interesting and a lot of fun but not for the average rider. Solution? buy an XT225 or a CRF300.

fuel consumption increased ?

what year this thing is made?

Unless it fixes some gremlin like oil consumption; I dont get the point of punching a bore over a few thou to gain 5hp.

Seems a lot of work and expense for what? 4 or 5 mph?

Puts gloves on while stripping engine but non when removing sump plug!

You'll need a bigger tank too😂

Idk why honda wont sell the Xadv 750 in America. It's a total shame

I don't know what was the expected power (probably about 14% more, just like the displacement) but do you know this would only increase the top speed of 4.5% ? This is definitively useless, in my opinion.

Swap it with daytona engine 4valve. .

By the time you buy all the parts you might as well have bought a DR400

You gotta do the exhaust dude you can’t just do a big poor kid and take a bigger breath and without being able to exhale it all

what's wrong with your honda is that it only got small intake valve ideal only for good fuel consumption and not for high speed. the multi hole injector is for bigger valves or 125 cc chinese motorcycle. a stock 125 cc chinese motorcycle are 27mm intake valve and 24 mm exhaust. your honda is tiny 22 mm intake valve.

Why not just buy a more powerful "adventure" bike that can keep up with highway traffic? Same situation as a motorized bicycle guy wanting to go 50mph, just buy a used Trail 90.

All the crap that comes with bikes now in times past screws on the carbi or a kit would have fixed it

I don't understand why people buy these then scream how can't go on highway and proceed do all kinds stupid expensive mods . Yeah these where never designed go at highway . Get the right tool for the job. The new honda xr150 is cheaper than a trail 125. used bikes from honda xr125 t0 250, nx 125, nx250 , kawasaki klr250, yahma xt225 xt250 tw200 are all cheaper than a new trail 125. Get the right tool for the job, then save yourself money and not have to do mods.

I did this same thing to my ex wife and she was NOT happy about it.

Hi, came over this video because I own a couple of Skyteam / Honda Dax 50cc and both are upgraded, one to 140cc and the other to a racing z155cc. That exhaust pipe inner diameter is 16mm on the Honda Trail 125cc - That is too tight, I have 28mm on anything greater or equal => 125cc or the airflow will suffer and the HEAT increase... Maybe a little tip, maybe increase the outlet pipe diameter!? Cool bike, but my Daxes rules... Cheers :)