Sprockets

[dmonkey]

Their diagram for the JTF274 shows a different countershaft diameter cut into the sprocket (15mm), so I don't think it would, but you could contact them to be sure.

They explicitly list the JTF273 as compatible with the 2021 CT125: http://www.jtsprockets.com/catalogue/model/s169/

 

[SLO]

A post by other member.

 

[SLO]

A post by other member.

 

[m in sc]

the reality of it is, the ecm will not allow much more speed overall unless you can get it unlocked or flashed. this has a lot to do with the timing and fueling tables. I know they are working on a flashed unit, its coming. For example, the stock 1st gen groms could hit an actual 62-64 gps speed right out of the box. different ecm tune. same head/jug/size throttle body and the exhaust was just as restrictive. put on a flashed ecm a cam and not much more and 70 actual was easy. I mean, look at the power difference #s on the supercub. it snot huge, but it IS different. its the exact same motor. different ecm number though.

On the trail, that's why i went the way i did, focusing on midrange. for ME, the reality is while 60 sustainable max of 65 would be ideal, its not really necessary and i don't want to try to go that way, if ever, until a flashed ecm becomes available. even then maybe not, its pretty good as it is.
the 143 piston and the cam w the efie and pxc 150 injector make the midrage much more grunty, but gave up no top end, gained a few mph and get up to 50-55 pretty quick, acceleration up hills is way better. flatland in current state i can hit 57-58 winding the piss out of it. downhill is another story, but you have to be careful as in gear, its trying to fuel the motor over the stock rev limit and things can go south really fast. just my .02

 

[SLO]

the reality of it is, the ecm will not allow much more speed overall unless you can get it unlocked or flashed. this has a lot to do with the timing and fueling tables. I know they are working on a flashed unit, its coming. For example, the stock 1st gen groms could hit an actual 62-64 gps speed right out of the box. different ecm tune. same head/jug/size throttle body and the exhaust was just as restrictive. put on a flashed ecm a cam and not much more and 70 actual was easy. I mean, look at the power difference #s on the supercub. it snot huge, but it IS different. its the exact same motor. different ecm number though.

On the trail, that's why i went the way i did, focusing on midrange. for ME, the reality is while 60 sustainable max of 65 would be ideal, its not really necessary and i don't want to try to go that way, if ever, until a flashed ecm becomes available. even then maybe not, its pretty good as it is.
the 143 piston and the cam w the efie and pxc 150 injector make the midrage much more grunty, but gave up no top end, gained a few mph and get up to 50-55 pretty quick, acceleration up hills is way better. flatland in current state i can hit 57-58 winding the piss out of it. downhill is another story, but you have to be careful as in gear, its trying to fuel the motor over the stock rev limit and things can go south really fast. just my .02

Thank you for the heads up! 60 mph would be a little buzzy. So many good back roads to keep me busy. Planning to go to ELK GARDEN WV. First back roads to Elizabethtown and Ridgewood BBQ.

 

[Tjdemarco]

I'm in the middle of Greater Kansas City and use my bike as a sidestreet commuter to downtown and as an errand runner. No off road riding until I get a trailer or a camper to get out in the countryside. The only thing thing that bugs me about my Trail is the short 1st gear. I can't get through an intersection without having to shift to second, usually at about 12 or 13 mph. I think the manual recommends shifting at 9. It's nice and smooth that way, but I feel like I'm in everybody's way poking along in traffic like that. Would a 15 tooth sprocket make 1st gear taller? And would it reduce acceleration from a stop, especially on an uphill?

 

[m in sc]

it would make them all 'taller'' 15 is a bit much, and def affect your acceleration in a negative way. see if you can go down 1 or 2 on the rear. wont be quite as extreme a change and will probably make things better in what you want. fwiw, i think i shift out of 1st at a higher speed, but not much. dont worry about hitting redline the motor is very under-tuned.

 

[Chatham125]

I've seen at least three members say the ABS fault light comes on, not just two, and we'll see a lot more as more bikes get out there and guys start gearing them down. People like the developers at Opmid, who testify this is correct, know a lot more about it than we do. To answer your question, when the ABS light blinks, that means ABS is disabled. And yes, I can verify, it is disabled until you turn off the key and restart the bike. It takes exactly, exactly, 10 miles on my bike of uninterrupted highway miles to make it come on. I'm assuming that when I'm off-road riding and stopping and starting and spinning the wheel a little, that is what keeps it from faulting. So it has to be highway miles. As far as gearing goes, as I mentioned, I was using gearcommander.com to report on the calculated chain and sprocket wear. Regardless what anyone thinks, there is no definitive way to measure chain or sprocket wear without a LOT of testing and measuring, something that may or may not have ever been done, but certainly not by anyone in these forums. You can choose to believe or disbelieve calculations, just like you can choose to believe or disbelieve Einsteins calculations on the Theory of Relativity or any other calculations that have ever been invented. That is certainly a personal thing. Some people just enjoy overlooking facts because they don't want to believe them and they feel they are smarter than the guys making calculations. And maybe they are. I won't argue the point. Enjoy your bike at whatever gearing you like on it. Chances are you'll never ride it enough miles (not being a long-distance highway bike) to ever wear out a chain sprockets in the years you own it.

I have ridden at least 30 miles 5 times with no ABS light coming on. I have the 13T front. My 125 is a Jan build 2022.

 

[Thepen]

the reality of it is, the ecm will not allow much more speed overall unless you can get it unlocked or flashed. this has a lot to do with the timing and fueling tables. I know they are working on a flashed unit, its coming. For example, the stock 1st gen groms could hit an actual 62-64 gps speed right out of the box. different ecm tune. same head/jug/size throttle body and the exhaust was just as restrictive. put on a flashed ecm a cam and not much more and 70 actual was easy. I mean, look at the power difference #s on the supercub. it snot huge, but it IS different. its the exact same motor. different ecm number though.

On the trail, that's why i went the way i did, focusing on midrange. for ME, the reality is while 60 sustainable max of 65 would be ideal, its not really necessary and i don't want to try to go that way, if ever, until a flashed ecm becomes available. even then maybe not, its pretty good as it is.
the 143 piston and the cam w the efie and pxc 150 injector make the midrage much more grunty, but gave up no top end, gained a few mph and get up to 50-55 pretty quick, acceleration up hills is way better. flatland in current state i can hit 57-58 winding the piss out of it. downhill is another story, but you have to be careful as in gear, its trying to fuel the motor over the stock rev limit and things can go south really fast. just my .02

Do you by any chance know if the cam/crank/rod/piston is the same on the supercub and trail? Maybe its as easy as an ecm swap, perhaps cam too, to get a steady 55-60 mph cruise speed.

 

[m in sc]

cam is the same, primary gearing is different in motor but crank the same. Ive ridden a supercub.. my wife actually has one . they are a hair faster stock.

21 model trail ecm is 38770-K2E-A01 , super cub is 38770-K0G-962 (which is the older interface (14-20) and physically wont swap ).

just a cam swap wont do it, ive been there + a lot more. Its def in the ecm. Ive contacted those who flash ecms for groms, they looked into the trail ones and verified what i thought.
But, the 2022 grom one does have the same interface. I ordered one from partzilla but they were having issues getting stuff shipped... so i cancelled that order and now have one coming from a different supplier, should be here monday or tues. will it work? not sure but im going to try it. It should.

 

[Thepen]

Did you order the 38770-K26-G11 one?, that's interesting. I wonder if it will work, I don't see why not. If it'll work the only thing I see different is the intake, ours is like a long tube compared to the groms shorter one, but I'm sure the ecm will quickly adapt to the dictated 14.7 Afr. Also, if the 2022 groms have the same interfaces as our trails, wouldn't the power vision 3 from 2022+ groms work for us as well?

 

[m in sc]

they say it wont.. however, not sure. what I was told was the auto clutch models (trail & cub) use a map sensor that the manual clutch models dont, and it can be bypassed by using a standalone unit (ficon/arracer, etc). However, the trail and cub ecm stock wont play well with piggybacks like the PV3 for this. My thought is that IF it can run well w a standalone not using this, then a stock grom ecm should work as well, and THEY can be reflashed. since the gen of ecms of the 22 grom and the trails run in constant closed loop, it should correct the fueling.. mine does. I have a eife on mine that sets it to 13.5 afr. however the timing table on the trail ecm is the issue, hence why im going to try the grom one.

 

[Thepen]

Understood. Very good info you've got there, I would kindly ask if you could let me know how that ecm works out! If possible of course. If that ecm will work, then that by itself will solve the dead top on these bikes. It would solve my problem, I'm trying to do a 143cc "big" bore with a pcx injector and a 15 tooth sprocket. Maintaining 60mph would be awesome. This bike really doesn't need much to be ideal.

 

[Thepen]

I did a little bit of digging and actually the camshafts are different. The trail, supercub, and groms have all different part numbers

Posted below are trail then cub

 

[dmonkey]

Crankshafts are different too, the Trail 125's is only in common with the Honda Wave 125i.

 

[Thepen]

And pistons as well, hmm. I wonder if the stroke distance on the piston is the same?

 

[Thepen]

Strokes x bores are the same. Cylinder heads seem a little different but valves are same size and cams are interchangeable between the older grom/supercub/trail/monkey. I don't know why would the pistons be different though. Its the same bore x stroke, same cc. Maybe slightly heavier piston in trail for more inertia= more torque? I think path of least resistance to higher top speed would be stock grom cam + grom ecu(if that works) or grom table values in our ecm's, which doesn't seem possible at the moment

 

[zamdrang]

After lots more miles and going back and forth between the 14 and 15t sprockets, I agree that there is just no substitute for power. My preference might differ from most in that in addition to more speed I'd like less buzz. The 15t helps, and I've added lots of bar weight and grip puppies and I still find it uncomfortable to ride for long. If it would go 55-60 I may be more forgiving but to me the lack of speed combined with the buzz is a big deal.

I would really love see whether a reflashed ECU and cam can make a significant difference in top speed. But I can't see it changing the buzz this thing has at almost any rpm and speed.

What has compounded this for me is I just picked up a `23 Grom. I'm not exaggerating when I saw its night and day in the vibration dept. There is literally no vibration in the bars up to about 45, which is as fast as I've taken it so far, still breaking it in. I would love to ride a new Cub and Monkey to see if this is unique to the Grom. My feeling is it's the motor rather than any tuning, mounting or frame differences, and the bar weights are tiny. But I could be wrong. It just feels more refined and better. Though not massive it does have noticeably more torque off the line. It must be subtle to most, I can't find anyone mentioning this experience between the old/new Grom, Monkey or Cub. But for me I find it to be a profoundly better motor in every way.

Given this experience I may just cut my losses and sell the Trail and see what Honda does with it in the future. Surely the new motor will put in it at some point, hopefully with the 5 spd. Or maybe even a bigger motor which is what it really needs.

 

[Thepen]

I don't really notice any vibrations. But then again I switched over to the trail as my daily from a single cyl 690cc husky. You'd hate that thing lol. I ordered a TB grom cam, I'll just try that, see what it does with the top end. I'll report on a separate thread, as this is a sprocket thread. My plan in the long term is 143 yuminashi mid bore kit, along with that tb grom cam and pcx 150 injector and the 15 tooth.

 

[m in sc]

the cams measure lift and duration basically the same, (yes i measured them). however the trail is slightly advanced for low rpm re pin location. there are other small minor differences but nothing i saw that was noteworthy. and i did try them all.

I have a 143, cam, pcx injector, etc. decatted exhaust etc, all this was documented on here. I also have an adjustable cam gear and tried them 2 degrees more advanced, and then 2 and 4 retarded. didnt make much difference in maintaining top speed. stroke is the same, cyls actually will swap right over. I even tried a 125 high compression piston. tb cam, etc. Im 99% sure its the ecm, and like said have one on the way.

This is the cam, the 143 cyl (i know it says 124 but its a sleeved stocker). and the yuminashi 238 cam. I can maintain 55 pretty well flatland, and on long flat runs touch 58-60. and im 205-210 lbs. So, it helped for sure some. the midrange and overall acceleration is vastly improved though.

these are the trail, grom and TB cam side by side.

I used my dial gauge and degree wheel in my mini lathe to compare them. TB cam was def better for high rpm. the 238 yuminashi cam is better from down low until about 9k. Thats why i went that way, Im not looking for an 11k screamer.

more importantly, i can maintain speed uphill. I know.. a big ask. lol.

But my final mechanical setup is the yuminashi 143 cyl w adjustable gear, the 238 cam, eife set to 21mV, pcx injector and modified exhaust. Over 1200 miles so far on that setup no hiccups. If the ecm works, then i should be good to 60-65 minimally. If not, then i'm going to try a separate stand alone timing controller

also, as aside note the grom heads/cyls WILL swap on w no modifications. ( i had a bunch of stuff leftover from my OG grom, then 2t swapped it later )