Oh my god this is the best video I’ve ever seen on ct trail mods. You’re the Project Farm of the Honda trail world. Great job, looking forward to your future videos.
Somebody should do a 250cc version of this bike. It'd be slightly heavier and slightly beefier. But i bet it would sell like hot cakes. Interesting video. Thanks Mr 😎
I have always thought the sweet spot would be a factory 175cc version with a 5 spd and manual clutch. I think 250cc would be getting past what the frame, rear swingarm and suspension/wheels are designed to handle. A well designed 175cc should be capable of running 60mph reliably and giving excellent bottom end for slower offroad use as well.
"I think 250cc would be getting past what the frame, rear swingarm ..." and brakes can handle, yup, I think so too, I'm bound to the 125ccm limit but I think with the tuning camshafts and a larger exhaust diameter, 12-13 hp are possible even with a 125ccm, here in Germany you can get on the motorway from 60 km/h, then you look for a truck that's doing 90 km/h and stick to it, ... but who drives on the motorway with a C125,@@billwiley7216?
@@billwiley7216 agreed the reason I sold mine was because it lacked the extra 4-5 hp that is needed to ride 60mph reliably. If it had that I would still own it
Personally having worked on and run the Z155 Zongshen motor, which is a similar design of engine, I would start with porting the cylinder head as it is free BHP (OK a top end gasket set) and match the ports to the gaskets and smooth out the ports. Next up I would either get a slotted cam sprocket, which is cheap enough or just slot the stock one and back the cam timing of to move the power a bit higher in the rev range. These things don't rev that high anyway with peak power at about 9000rpm and slotting the cam sprocket lifts peak power to about 9250rpm but helps let the engine hold onto the power for longer. My Z155 on the dyno is 14.6bhp and in stock trim was 13.2bhp. But it is not the peak power gain which is important as 1.4bhp is not a massive gain, but where it shows the most is at 11,000 rpm where the stock engine was 10.5 bhp and after tuning it was 14 bhp so it is a 3.5bhp gain over stock. If you need more power still then I would go for the 143cc big bore kit. BUT regardless I would still suggest running an oil cooler as these engines don't have the best design for keeping them cool and the bottom end is still close to the original 50cc motor and these get hot and heat will kill power. The oil cooler just adds a bit of security that it will not overheat or increase heat related wear when using it on trails.
Agree. we tune these engine here in Vietnam and Thailand. Porting + bigger exhaust manifold will help alot. 5 speed swap also cherry ontop (-2 rear sproket maybe decent for highways)
When I was into endurance racing engine tuning, we found that _not_ smoothing the ports actually worked better at reducing airflow instabilities. It's a common misconception that rough ports are bad, but golf balls are actually more aerodynamic than ping-pong balls. Those little dimples provide a smoother overall surface. They do this by housing small pockets of gas, which the rest of the air/fuel mix glides over, a smooth surface drags this airflow into the port walls, slows it down and goes unstable. Because of the way we peened our ports, our engines were noticeably smoother running throughout the rpm range, pulled harder out of corners and generally lasted a lot longer. Same thing with the inside surface of the combustion chamber and the piston crown, but for a different reason. Smoothing these surfaces bounces heat back into the gas, so the burning charge is slightly hotter, but this is a bad thing because that hotter exhaust gas has to pass the exhaust valve...cumulatively heating them up more than it should. The pistons also get hotter than they should be, heating up the engine oil until it can no longer cope, the piston and rings expand that bit too much and seizes the whole thing up. Not once after shot-peening the surface on the combustion chamber + piston did we burn out an exhaust valve, but other teams regularly found theirs overheated, bent and seized. By all means, port the heads to optimise the shape and volume...but I'd advise anyone to ignore the myths and hype around _polished ports_ because it's all total nonsense.
@@mazdamaniac4643 I agree smooth ports do not do as much as people think. Also a lot of people will just open up ports and not think about how air will flow into the engine through the port too. Making the air flow as straight as possible from inlet to the valve opening and working on the port floor is important. As for dimples, I am less sure dimples really do as much as people think as the dimples on a golf ball are for a different purpose and it is to break up the low pressure zone behind the ball which would hold the ball back and the dimples do let it fly further. But this is improving a ball shape because you don't hit an arrow shape or oval ball in golf. The ball is spinning and there is none of that in a port also the gas speed through the port is higher than the speed of the ball flying through the air and the faster you get a golf ball to go through the air the less the dimples help with distance. But a rough surface does break up the boundary layer of the gasses in the port and help turbulence and getting the fuel mixed with the air and better combustion.
I watched Part 1 and just finished watching Part 2 of the video series explaining this experiment to get more power for your Honda Trail. I found it interesting and educational. As a relatively affordable upgrade for the Honda Trail 125 (now 143cc), it's an appealing solution. That said, it seems the overall limits of the Honda Trail continue to manifest. As a "do it all" bike, the demands of highway riding or heavy loads of cargo (or rider) continue to push the envelope of what the bike's engine can accomplish. Or, put another way, the engine's power output remains the "limiting factor". Thanks for sharing your upgrade adventure. 🙂
the biggest restriction is the exhaust.. just look how small is the pipe. with a bigger exhaust, not necessary louder,you will se huge great improvment 😊
This right here is making me want this for a great first fun motorcycle. I’m a father of 4 so I don’t need a death machine to have fun while puttering around town haha. I’m glad I found your video should I get a Honda trail 125 in the next year but would want a little more speed but nothing crazy at all. Thanks for your time and effort to finding a great upgrade option!
My first time seeing your channel and that was a wonderful video. I have a 2024 Honda XRM 125 in the Philippines and that extra power sounds wonderful. How did it affect your fuel economy? I am getting 65 km/litre here which is 153 mpg. And I ride her as fast/hard as I can most of the time.
I honestly don't think it has changed that much. We put ~90 miles on it between fills and it takes around a gallon +/- so its still good enough for us.
Thanks for sharing your well produced video. The attention to the details and information you share is very helpful and greatly appreciated. I would like to know why you decided to go with the Yuminashi kit as opposed to other options such as the Tagegawa? Would you mind to share the full parts detail that you ordered/installed on the bike? Keep up the great work!
Would be cool to see it on full e85 with a bigger injector to see if you see or feel any improvements. While it does still make more power without increasing the timing, you wont be able to use its full potential but will be much safer at 105 octane.
For a pure race car or something with a flex fuel sensor and programmable ECU, E85 is great. I had a vehicle set up for E85 once and it was a pain (carburetor) because E85 isn't sold at every station.
I put a 135cc injector on my honda 125, at first my sparkplug is soaked with gas and increased the idle speed. Checked the sparkplug and looks normal again
Thank you very much for making this video and the 143cc BBK instal video. They are super well done and exactly the info I was after to mod my 2020 Super Cub C125. One question I have is do you think the cam is also worth it? Thanks Again!
I did forget to mention the cam was included in the $313. If I were to do it again, I would strongly consider sticking with the factory cam. The factory cam has a compression release so it was much easier to start, you can definitely tell the difference in cranking speed. The kick starter is almost worthless now. One of these days I might throw the factory cam back in and redo the test just to see if there is any real difference.
Another big-bore kit that doesn't come with a counter-balanced crankshaft to match the bigger heavier piston. You're on borrowed time, mate. Just pulled a Royal Alloy scooter engine apart that had been fitted with a big-bore kit by a bike shop, mate was furious when I found that the big end had ovalled and the crankshaft was bent. Wideband lambda sensor is a good idea though, stock sensors are _okay_ but fitted to a price. What it really needs is putting on a dyno and tuning all the fuelling values properly. Until you do that, you're pretty much throwing money away by chasing a guess that's based on assumptions. A skilled tuner at a reputable, professional dyno shop can always do a better job.
The larger piston can still be the same mass as the previous piston, just thinner or shorter skirts, etc. I didn't weigh them, but it would have been interesting to do so.
I don't know the engine has enough torque to go that much faster. It would probably go faster losing a tooth up front. Regardless, the tires are only rated for 60mph...
I wonder on how much the cylinder temp change after the BBK was install , I'm thinking of getting one for my grom and i personally dont like the look of the after market oil cooler .
Probably. It looks like there is more restriction in the exhaust than the intake and I'm sure the cam would be more effective if it could breathe better.
