'238' cam, for lower end/midrange installed

[m in sc]

So, not wanting to make this a rev happy motor more than it is, ive recently been running around with a stock 1st gen grom cam and a 143 big bore. othe rmods also include stuff ive listed in here before, ie" decat head pipe, eife 02 sensor 'device' and a pcx125 injector.

The TB cam did well but was kind of rev happy. since it was made for the grom, i can see this. the ecm on the trail is def different, so i figured id try the yuminahi 238 cam with it, and an adjustable cam gear. these are cheap upgrades over all.

heres a link to the cam:

YUMINASHI S-238 CAMSHAFT (MSX/GROM125 & SF - Z125 MONKEY - CT125 / C125...)

YUMINASHI S-238 CAMSHAFT / NK-SERIES (MSX/GROM125 & SF - Z125 MONKEY - CT125 / C125...) (14100-K26-238S)

www.yuminashi.eu

the cam gear can also be found here. shipped both were 174? bucks and received in less than a week.

now, advancing cam timing will yield more bottom end, and this cam is NOT aggressive, its more like an 'rv' cam for those familiar with automotive terminology. and.. can be used with a stock cam/piston.

I installed this and have been riding it for a few days to let the ecm learn. I can say it did exaclty what i wanted it to do, the midrange and lower end is great, with no sacrifice to topend. Im sure the fuel mileage might be affected a bit but meh. not much so far.

the only 'permanent' mod i had to do was remove the 2 ears inside the cam cover to clear the larger cam sprocket.
I think even the pack mule riders that never go over 45 mph will really like this setup. I can now just power up hills i used ot have to downshift to get up w out losing speed.

Top-end is about the same, but i might gear it a bit differently now since theres noticeably more torque.

 

[Shoot870p]

Thank you for the info. I’m glad you “tweak” these things for us and then give the details.
shoot870p

 

[m in sc]

I love tinkering with this stuff. figured I'd wait a few days of riding before I wrote a post about it. For me, i usually go way to far in the extreme, its different for me to look for that 'middle ground' ( ie vs stuffing in a 181 big bore and just going nuts). This cam really suits the power i think most people would want out of this.

I would think that just swapping the cam in a stock bike would yield desirable results for almost anybody on here. IMHO... I'd go for the bigger injector as well, but i think that might be as far as most would want if they like the bike stock but could use a bit more meat in the midrange.

as a side note, it was around the 75 mile mark before I feel the ecu had learned fully, thats with mixed in town riding and traffic and a bit of open runs on 2-lane back roads.

 

[AZ7000']

With the stock 125, if I understand you had good results with the 238 cam linked above, pcx125 injector (or is it a pcx150?), and the EFIE controller. Is this the adjustable cam gear (and how far would you advance?) I'll probably go to town on trying to decat the silencer too.

ADJUSTABLE CAM TIMING SPROCKET (HEAVY DUTY) (110CC / 125CC ENGINES)

YUMINASHI ADJUSTABLE CAM TIMING SPROCKET (HEAVY DUTY) (CRF110F - MSX/GROM125 - Z125 MONKEY...)

yuminashi.eu

 

[m in sc]

2 degrees, nothing crazy. yes pcx150. yes. that's what i currently still have.

 

[jeffcutten]

Dyno graphs and setup info for a very similar timing sprocket are available at:
cameronjonesracing.com/products/adjustablecamsprocket

 

[m in sc]

yes, true. just a point though: keep in mind the lower RPM redline of the trail ecm vs an open/tuned grom ecm. thats why i advanced it, no point in trying to make power past the rpm the motor can spin at.

 

[Flash]

From wht I havecread thus far the ECU in a JA65 model has some very distinct limitations. Something about closed loop tuning at certain throtle positions. Open loop tuning is only above 80% throttle. To me this means that no matter what injector one has the ECU will tune air fuel ratio to presets which are notoriously lean. On my bone stock Canadian JA65 2024 it seems far to lean overall. Euro 5 emissions. What is the cure without excessive noise or high dollar parts. The only thing i did was cut out the spark screen as it was very restrictive.

 

[Salty Sway]

What is the cure without excessive noise or high dollar parts.

With those restrictions not improvement is possible. A free flowing exhaust will be louder, ask opinions on what's loud and everyone has an opinion. Some think an open pipe on a KZ100 isn't to loud.
Add more fuel - need a way to exhaust it
Add exhaust and more fuel helps
Add a cam and more fuel is needed and a way to exhaust

 

[Flash]

With those restrictions not improvement is possible. A free flowing exhaust will be louder, ask opinions on what's loud and everyone has an opinion. Some think an open pipe on a KZ100 isn't to loud.
Add more fuel - need a way to exhaust it
Add exhaust and more fuel helps
Add a cam and more fuel is needed and a way to exhaust

Indeed. So a mild modification to the internals of a stock muffler might be good enough for now. The Tuner to fit JA65 models is still $497USA. Someone else posted a link to that.

 

[m in sc]

unless you're going to throw it on a dyno to tune or fit a wideband to monitor, IMHO is just pissing money away.

 

[dmonkey]

I would also check with Takegawa about using that FI-Con on a USA market ECM before purchasing it, since their primary market is likely Japan.

SpeedTek/ARacer only list support for the "CT125 2020" on their site so you'd want to confirm comparability, but for less money than that Takegawa piggyback tuner you could buy the ARacer RC MiniX standalone ECU. Like @m in sc says though, you still need to tune it. Another option there is ~$320 to add the AF2 wideband O2 module for auto tune, and then you need to get the wideband O2 sensor bung welded into the exhaust which it sounds like you already plan on reworking.

 

[RustyRodder]

Hey M- do you recall what mark you put your camgear on? I saw in one video that you need to put it at 2.5* advanced to equal stock, but that was on a grom.

 

[m in sc]

not off the top of my head.

 

[Flash]

My cheap free flow exhaust used to be on a Harley Davidson 1200 Sportster. $40 for a pair next to new condition. Looks nice and shiney. Can now hear the motor at least. By no means is it loud. I think it leaned out the WOT Air Fuel mixture at transition point from 80% to WOT Ordered in a Honda branded PCX 150 injector. Plan to install and let the ECU learn the new rate. Might have access to a Grom 105cc or 115cc used injector from stock 2023 model if it turns out to be to much. Harley Makes nice Chrome parts.