HONDA CT125 Big Bore Kit

[STUBBORN]

watched a YOUTUBE of a Trail 125 mod in Thailand

Honda CT125 Locked & Loaded Big Bore 142cc​

YouTube

www.youtube.com

 

[AZ7000']

I’ve seen the video, any ideas on if we can buy it here? I think he used a oem Honda version?

 

[G19Tony]

I’ve seen the video, any ideas on if we can buy it here? I think he used a oem Honda version?

If I were to do something like this, I’d feel better using Honda parts.

 

[r80rt]

Have fun grenading your engine boys!

 

[Lostagain]

The big bore kits seem to get rave reviews from those who have installed. I'm prone to think that anyone who invested time and money into a project is predisposed to see the outcome in the most positive light. Since the new piston is bound to weigh significantly more than OEM I don't see any way around getting more vibration and eventual wear due to the imbalance. Long ago I installed a big bore/high compression setup in my Ducati. Balancing the crank made the final product smooth as silk but probably doubled the cost of the whole project.

 

[AZ7000']

I’ve seen the video, any ideas on if we can buy it here? I think he used a oem Honda version?

Have fun grenading your engine boys!

I ride this to work every day, use it for most downtown errands. 1975 and running strong. Asking isn't doing...

 

[r80rt]

I rode this and two others for many years, tough little rascals.

 

[m in sc]

big bore kits up to 160 wont grenade amotor, calm down. any one for a grom or a monkey will fit. the 143 kits are a good simple upgrade. go much bigger its ecu and injector time but no ecu upgrades available yet. but the injectors are. what grenades a motor is high rpm for long periods of time and running extremely lean. mY rod broke in my old motor at 12000 rpm doing 75 mph as i shifted into 4th gear. totally my fault. so, dont do that. lol. there';s LOTS of these motors running for many years at 180cc+. contact hard racing for big bore kits domestically.

 

[STUBBORN]

Hi, I hope Honda upgrades the Trail 125 to a Trail 150 for 2022. Rumor that Honda may be releasing a Honda CT 150 Hunter in Japan this June. As for the 150 cc engine, Honda can just choose from its inventory of available engines. And, since the Hunter Cub is already being sold in Japan, Thailand and Indonesia, the easy choice for Honda is to pick the engine being shared now by the CB150R, Supra GTR 150 and the CBR150R. See picture below,

 

[TrailBoss]

Hi, I hope Honda upgrades the Trail 125 to a Trail 150 for 2022. Rumor that Honda may be releasing a Honda CT 150 Hunter in Japan this June. As for the 150 cc engine, Honda can just choose from its inventory of available engines. And, since the Hunter Cub is already being sold in Japan, Thailand and Indonesia, the easy choice for Honda is to pick the engine being shared now by the CB150R, Supra GTR 150 and the CBR150R. See picture below,

I'd never turn down more power, but I wonder if more engine is really needed. Maybe in the US market where riders are bigger and heavier, but otherwise I'd say the 125 does a decent job if you use it for what it was designed for. No bike does everything well, the Trail 125 is no exception. The real reason I doubt you'd see a 150 in the short term is simply due to economies of scale. Honda has to manufacture more 125 mills than 150s, though I could certainly be wrong. Plus a 150cc will move the price point Northward, which is rarely a good thing.

In any case, I'd take it, don't get me wrong.

 

[r80rt]

Yeah, I think the 125 is great the way it is, and when used as designed it as close to perfect as I've seen. Not holding my breath, but if the 150 comes along I'll get one.

 

[bustupbiker]

If Honda were to upgrade ( engine wise ) the bike it would no longer be a Cub. The Cub has semi Auto gear change with the clutch on the peddle.
None of the engines in the bikes in your post have that feature...Just thinking

 

[STUBBORN]

I spoke with a new Trail 125 owner in northern NH today. He is only 5 foot 9 - 180 pounds.
The bike reaches over 45 on the road but slows down considerably climbing the
steep NH hills. He could not get over 35 on Route 112 (Kanamangus Highway.)

"Ayuh, thought i was gonna be a hood ornament fer a bit. T'was ascared."

 

[Fun4me]

Don't fix it if it's not broke. It took Honda 35 years to start selling these in the U.S. again. They're selling as fast as they can build & deliver them. I don't expect to see any significant changes any time in the near future. But I guess we can all dream and hope.

 

[m in sc]

i mean, used as designed is a really subjective issue. its just a supercub, with a grom motor and different bodywork and exhaust. I commute on mine, which is exaclty what i bought it for and since it has all road gear.. thats what its for. for me.
I will be taking it to some nostalgia dragraces tomorrow on the rail on the back of my 66 galaxie to run around the track and swapmeet w my GF on the back here and there. also what bought it for

fwiw, i rode it out to a bike-night yesterday and can hit a consistent 55 mph and i'm 212 lbs in full gear. wait till i decat the pipe and weld up a new head-pipe. should be able to hit 60 consistently, and that would be fine with me, buit retain the stock muffler. None of this makes it any less use-able at low speeds either. neither will a bigger bore kit. .02

 

[jpcaudill]

I spoke with a new Trail 125 owner in northern NH today. He is only 5 foot 9 - 180 pounds.
The bike reaches over 45 on the road but slows down considerably climbing the
steep NH hills. He could not get over 35 on Route 112 (Kanamangus Highway.)

"Ayuh, thought i was gonna be a hood ornament fer a bit. T'was ascared."

I find this to be a bit surprising. I'm at 7000 feet in Colorado - I'm 6' 5" and weight about 180 as well. Typically hitting 50 and sometimes 55 mph on flatter terrain isn't much of an issue. On some really gnarly climbs, I can lose 10mph - so maybe 40. I don't know what route 112 is like in NH but I have to imagine the elevation isn't as much of a factor so I'm surprised to hear it would struggle as much.

 

[STUBBORN]

I find this to be a bit surprising. I'm at 7000 feet in Colorado - I'm 6' 5" and weight about 180 as well. Typically hitting 50 and sometimes 55 mph on flatter terrain isn't much of an issue. On some really gnarly climbs, I can lose 10mph - so maybe 40. I don't know what route 112 is like in NH but I have to imagine the elevation isn't as much of a factor so I'm surprised to hear it would struggle as much.

Yup, Agree with you. I heard that you can do 55 as well. The mountain roads in NH were built a long time ago. The grades are very steep. The hairpin turn is posted at 20 mph, and the reinforced guardrails have a lot of scars. People just won't slow down. The fact that you lose 10 mph going up may be a safety concern considering those the speeding drivers. Much more so, they may not be able to stop going down those steep grades.

 

[jpcaudill]

Yup, Agree with you. I heard that you can do 55 as well. The mountain roads in NH were built a long time ago. The grades are very steep. The hairpin turn is posted at 20 mph, and the reinforced guardrails have a lot of scars. People just won't slow down. The fact that you lose 10 mph going up may be a safety concern considering those the speeding drivers. Much more so, they may not be able to stop going down those steep grades.

Ya that's a good call. I think my viewpoint is probably a bit askew because I road bike and so being on a motorcycle doesn't feel all that much different - I'm aware what's around but ultimately don't focus on it much and pray drivers make good decisions. Although on the flip side I know the average joe doesn't understand the difference between 50CC, 125CC or 650CC and there's probably a perception there should be no difference.

 

[m in sc]

On rides in the mts i regularly come up on big cruisers going 45-50 mph by choice so Im not sure its a big a concern as some think.

Im taking the 125 to the mts this weekend plan on riding the Cherahola skyway at least once if the weather holds out. Will report back after trip. But im not concerned about it, at all.

 

[dmonkey]

There are at least tens of thousands of Big Bore Kits up to around ~180cc in size from reputable brands that have proven their reliability in Groms and Monkeys with this motor already. I mention up to that displacement because the kits beyond that often require splitting the cases, are more expensive, and require more frequent maintenance so they are not as popular. If you want to use parts from Honda for it then you may be missing the point, Honda is manufacturing these engines for efficiency in all regards: tooling, cost, performance, emissions, reliability, etc. If you're going to take the time and spend the money seeking performance, then it's no different than upgrading from the OEM suspension, you'll be getting a higher end part/kit from a reputable company that has purpose built it as an upgrade rather than going with OEM parts.

Some things to consider with the BBK's are that there are a lot of other parts you'll want to upgrade with it to get the most out of it and that's where you can really spend some dough chasing performance and all the air, fuel, oil, cooling, and reinforcement upgrades that go with it, but for this motor it's a lot cheaper to double the horse power than it is to double it on a v-twin!

For anyone who does really want soup up this motor beyond a simple BBK top end kit, right now a limiting factor on the market seems to be that the CT125 uses a different crankshaft than the Grom, so AFAIK right now there isn't a forged crankshaft or a crankshaft support bearing that fit it on the market yet. So if you do go with a really performant kit it would be a good idea to gear it so that you can keep it out of high RPMs for any long duration. Looking forward to when there is a forged crankshaft available though!

All that being said, the bike is great fun bone stock at just 125cc, quite an improvement from the 110cc. It's all relative to what criteria you're evaluating it against.