HONDA CT125 Big Bore Kit

[m in sc]

from wayyy back. (grom specific but still)

Fuel injector flow rates

www.hondagrom.net

 

[QuantiQualification]

For those interested, here I am yanking my second Yuminashi piston out.

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[dmonkey]

Sorry if I missed it in a prior post, but how are you tuning this Yuminashi 164cc setup?

 

[QuantiQualification]

Sorry if I missed it in a prior post, but how are you tuning this Yuminashi 164cc setup?

So, for the previous setups, one with and one without the Takegawa pod air filter, I built custom fuel maps based on maps that Takegawa built for the CT125 on their piggy back plug and play FI CON unit that comes with the hyper-e stage 143cc kit. There is a map for a 125cc with my modifications and a 143cc with my modifications with the air filter. I interpolated what 164cc would look like from that. There is a map with my modifications for a 143cc and a 181cc without the Takegawa air filter and interpolated the 164cc with standard airbox from those. The "map" they use appears to be additional microseconds of injector timing on top of the called out time from the ecu. So a stock setup would have all zeros for all rpms and throttle positions. With a BBK, the times would (usually) be greater than zero up to a maximum of 5000 microseconds. It is going to be challenging to use the stock airbox with a larger injector because I do not have a map to really base that off of. I do have a map with the takegawa air filter with larger injector for a 181cc kit but I am not planning on using the Tak Air Filter for the next build.

So in brief, I am using tuning values Takegawa worked up on their dynos and then guessing and interpolating to my 164cc setup. The reason I think (thought) it would be okay, is the ecu will adapt to slight variation if my values are a few hundred microseconds one way or the other. The 143cc setup that I originally put in followed Takegawa's setup and built map exactly. That setup ended with piston slap.

 

[QuantiQualification]

First set with Takegawa Pod Air Filter. 125cc, 143cc, 164cc

 

[QuantiQualification]

Second set without Takegawa Pod Air Filter. 143cc, 164cc, 181cc

 

[dmonkey]

Do you have something set up for monitoring the AFR? The stock sensor is likely a narrowband o2 that just tells rich or lean compared to stoichiometric, a wideband o2 sensor is needed to measure it. It's a much better feedback mechanism than melted pistons

 

[QuantiQualification]

Very interested and I have heard about it being talked about before. Realistically, how does one go about installing and monitoring in real time?

 

[m in sc]

weld a wideband o2 bung into the exhaust and fit a gauge.


they used to sell (doebeck maybe?) an adapter to run a wideband at the stock location, i had that AND added a second one on the grom to do comparisons, they both always read identical.

heres a bosch wideband senor in the stock 02 sensor location. yes, it worked, but you need the adapter. you can feed one of the wires (not sure off top of my head) to feed the ecm like a narrow band so it doesnt throw a code.

 

[dmonkey]

^^^ What @m in sc said.
Here's a "cheap" kit where you'd just need a bung added to the exhaust for the larger (18mm) wideband o2 sensor: https://www.glowshiftdirect.com/tinted-7-color-digital-wideband-air-fuel-ratio-gauge/
Plenty of other options, there are even ones with display mounts specific to the Honda Monkey handlebar clamp that might fit on the CT125.
Aftermarket exhausts sometimes add a bung for that lambda sensor(s) with a removable plug bolt in it, but I haven't noticed a CT125 exhaust with it yet.

For a less DIY option, you could see if there's a motorcycle shop in your area that offers tuning service and would take it on. It would be hit or miss if they'd be willing to work with your fuel controller since it's not a common name brand one in the USA (assuming you're in the USA since it's a USA spec bike). That Takegawa FI Controller is likely the same as a Dilts Japan Enigma piggyback fuel controller just with SP Takegawa branding. It would cost you a pretty penny to get it professionally tuned, but if you're going to be running the same engine build for a while it might be cost effective as a one-time thing to get it tuned right on a dyno without melting more pistons or futzing back and forth with with the fuel map between pulls on the street (or preferably somewhere other than a public road) staring at an AFR gauge while you ride.

Also be sure to blueprint the ring gaps for the cylinder bore diameter that you're using. Here's a good demonstration on gapping the rings.

 

[m in sc]

don't brain fuck it to death, just get a quality afr gauge and adjust as nec. the autometer setup was 200 bucks and high quality. I've tuned quite a few bikes and cars with that gauge. look for the adapter for the stock head heck, I might still have mine

 

[QuantiQualification]

M in SC, I am not sure if your last post is suggesting a narrow band AFR gauge or a wide band . . . If you are suggesting narrow, please forgive the question below.

Would a narrow band AFR gauge that plugs into the stock O2 sensor have any utility or just a waste of time/money? I am not terribly opposed to drilling and adding a bung to the muffler for a stand alone wide band, just not sure how the Takegawa (Dilts) piggy back/ecm uses the stock O2 sensor and not sure messing with that will lead to some issues. I do not have welding capability at present hence the question above.

 

[m in sc]

wide band. this threads right in stock location.

https://www.woolichracing.com/products/ducati/multistrada/0/564/narrowband-to-wideband-o2-adapter.aspx

ive used it, it works. that being said, id have to dig see which wire off the wideband will go to where the old narrow band wire went. the pic i posted was with a commited welded in wideband 02 in the exhaust feeding the power commander, and a second one temporarily in the head with one of those adapters so i could use my readout gauge (before i bought a dynojet one). the laptop is reading off the exhaust system 02, and the head one is feeding the gauge. the point behind that pic was to show they read the same, since i wasn't sure if the adapter would actually work as described since the head of it was so small. it always matched.

In your situation, i would get a decent afr gauge, and an adapter, and monitor that to write your map. when its written, then you can remove it and go back to the narrow band setup. like said, im surprised the controller didn't have an auto tune feature or read off a wide band. my .02.

if you were closer we could weld an 02 bung in your exhaust in about 15 mins. its pretty easy. maybe find a local exhaust shop that will do it for you? then you can just cap it when not running the gauge.

welding ability has its benefits, thats for sure.

 

[QuantiQualification]

After giving this some thought, I am going to do the AFR thing in two phases. I am going to start with a super cheap narrow band AFR that plugs in and taps the signal from the stock O2. That will help me (hopefully) to not blow the thing up again. This is just to make sure I am always running in an overly rich condition. How rich? I will not know. I also found out that the Takegawa FI CON does report out fuel injector duty cycle, that would have been nice to know before ! and . . . they recommend not going over 96% duty cycle. Crap. So if my Fuel Injector was even a little under spec . . . . Then, at some point when I am seeking a little bit better, cleaner power, I will install a stand alone Wideband O2 + AFR or get rid of the Takegawa FI CON and replace it with an autotune, possibly from Dobeck. They are not currently selling though. Waiting for some sort of bluetooth upgrade.

 

[m in sc]

well, thats better than nothing. ive heard of people tuning with a narrow band. it should at least get you safe.

looking forward to the result.

 

[RustyRodder]

After giving this some thought, I am going to do the AFR thing in two phases. I am going to start with a super cheap narrow band AFR that plugs in and taps the signal from the stock O2. That will help me (hopefully) to not blow the thing up again. This is just to make sure I am always running in an overly rich condition. How rich? I will not know. I also found out that the Takegawa FI CON does report out fuel injector duty cycle, that would have been nice to know before ! and . . . they recommend not going over 96% duty cycle. Crap. So if my Fuel Injector was even a little under spec . . . . Then, at some point when I am seeking a little bit better, cleaner power, I will install a stand alone Wideband O2 + AFR or get rid of the Takegawa FI CON and replace it with an autotune, possibly from Dobeck. They are not currently selling though. Waiting for some sort of bluetooth upgrade.

Sounds like a better plan!! A little overkill.in injectors isn't a bad thing. In my cars, I've always tried to stay under 85% duty.

If you do sell that ficon, let me know!

 

[QuantiQualification]

Okay . . . what gives? I got the KOSO MINI 3 AFR that is designed for the Grom. I assumed the O2 sensor would be the same with the same connectors. I am wrong. The O2 sensor on the Honda Trail is a 2 pin, 2 wire while it looks like the Grom is a one pin, one wire? Thoughts?

 

[m in sc]

i could swear mines a 1 wire. actually, it is but in a 2 pin connector for some dumb reason. heres the stock o2 wire i clipped and added in a bullet to interrupt the signal to run the efie unit, black w a red tracer. i do remember the grom having a single pin connector. id splice it in.

 

[QuantiQualification]

Ah . . . That makes sense. Already put it all back together. I guess I will skip the narrowband and go straight to wideband when I am ready.

 

[QuantiQualification]

Fuel injector was the difference. Thank you everyone for your help!

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