Honda Monkey Tune

[Deoodles]

I had a 2014 Grom when they first came out. It was a great bike. The motor was impressive but there wasn’t a lot of aftermarket support for them and I sold it. When the Monkey came out I went and looked at them but wasn’t ready to end up in the same situation. I’ve done a lot of reading and have spoken with a tune shop to learn about tuning and the potential of these motors. I Have my 124 Stroker and it’s as big as I am capable of going with it. No complaints it is what it is and can hold its own but, I’m done spending $$ on it and it’s time to enjoy it. I wanted a guesstimate on HP so I could put a Monkey build together that would out perform my 124
Here is my new project. I didn’t want to purchase it until I found support I was comfortable with. The goal is to get it to cruise at 60 and I don't care what it does after that (Thanks Fatcat).

Monkey Build

Cam, TBW1050
Exhaust, SP TAKEGAWA Sports Exhaust. (04-02-0295)
Dinger Built intake
Cameronjones racing DynoJet mapping.
14/34 sprockets. (Stock is 15/34)

I bought it today and will collect the needed parts while I gently break it in. I haven’t purchased any parts yet but the goal as Fatcat stated, a flat torque curve that pulls into 60 and beyond. My goal is to do that while keeping it a 125 if I can.

 

[OLD CT]

I had a 2014 Grom when they first came out. It was a great bike. The motor was impressive but there wasn’t a lot of aftermarket support for them and I sold it. When the Monkey came out I went and looked at them but wasn’t ready to end up in the same situation. I’ve done a lot of reading and have spoken with a tune shop to learn about tuning and the potential of these motors. I Have my 124 Stroker and it’s as big as I am capable of going with it. No complaints it is what it is and can hold its own but, I’m done spending $$ on it and it’s time to enjoy it. I wanted a guesstimate on HP so I could put a Monkey build together that would out perform my 124
Here is my new project. I didn’t want to purchase it until I found support I was comfortable with. The goal is to get it to cruise at 60 and I don't care what it does after that (Thanks Fatcat).

Monkey Build

Cam, TBW1050
Exhaust, SP TAKEGAWA Sports Exhaust. (04-02-0295)
Dinger Built intake
Cameronjones racing DynoJet mapping.
14/34 sprockets. (Stock is 15/34)

I bought it today and will collect the needed parts while I gently break it in. I haven’t purchased any parts yet but the goal as Fatcat stated, a flat torque curve that pulls into 60 and beyond. My goal is to do that while keeping it a 125 if I can.

View attachment 68460

Congrats! Good luck with it Ray.

 

[kirrbby]

Congrats on that awesome new bike Deoodles.

I was fortunate to get to ride one recently. I was pleasantly surprised that it exceeded my expectations a bit. Brand new Honda. It's a substantial machine. It was just effortless power right up to about 50 or 52mph. Then it started to work to inch up a few more.

I've read thru your other thread, and seen your goal on this one.
It sounds like you want that SAME kind of effortless power...but up to about 65...then settle back to 55-60, @6700rpm, AND you want that from 125cc. Seems to me that if it were that easy, Honda would be doing it.

I think, if you can reach your goal, MILLIONS of people will be coming to lilHonda to see how you did it...millions.
But you have the right "stuff" to get it done, and some other smart folks here to help you. Plus, the Xtra gear will help.

Love the thread already.

 

[fatcaaat]

If you are looking to achieve a 60mph cruising speed with a 125cc engine you are going to find that challenging without ringing its neck. You'll need to be running that at like 8500-9000 rpm sustained to do that, which is above (at least IMO) the design limits for any type of longevity to this motor. When you say cruise at 60, I read that as, "I want to run this on a road where I can go 60mph 10-20 miles at a clip" So to that, I say, no...you're not going to achieve that with the aforementioned setup.

A few thing that might help you on your journey though. Lots of power can be gained from the head and piston. I'd suggest you send the head out to Chad Norman and have him rework the ports, update the valves, and massage the chamber. Match that with a different piston and you might have a chance.

I suspect that if you run this motor sustained at 8k+ rpm it's going to have a much shorter life. Ideally, the long term cruising RPM for these honda Singles is right around 7K give or take. So, perhaps you need to first start with a gear calculator to determine what combination of tire and sprockets and transmission ratios give you 60mph at 7k. Then you'll need to go about configuring the engine to achieve the ask....and this is where I have my doubts about your suggested combination getting there.

Case in point...I have a bunch of different bikes in different configurations. Two of these achieve the goal (non are innova FI motors). The Nice 176+r makes right around 22hp. It is geared to do 62mph at 7Krpm. It does it without complaint. THe second one is a Honda Nice 142cc...this one uses a 62mm stroke, 54mm bore, lumpy cam, and quite of bit of portwork to the stock head. This is geared to do 58mph at 7k and it runs out of air due to the smaller ports and valves around 8500. Lastly, I had a Nice 127cc 4V+r engine. This needed 8200 rpm to produce 60mph and I simply wasn't comfortable running it that way for long periods of time...and even though it had a large oil cooler on it, it would get hot if I pushed it.

So, based on my definition of cruising, I think your goals are quite ambitious. I simply think you are going to need more displacement.

 

[69ST]

So, based on my definition of cruising, I think your goals are quite ambitious. I simply think you are going to need more displacement.

That's it, in a nutshell. Gearing requirements are determined by torque and that's tied to displacement. That said, while increased bore size will boost torque, any increase will be modest, regardless of hp numbers. Most of the hp increase from a larger bore manifests as superior breathing...and that means increased rpm, the opposite of what you're after. Increased stroke length disproportionately affects torque and, with it, gearing. For your stated goals, more displacement...based off of a stroker crank...is the way.

 

[Deoodles]

Thanks for the input. If I recall my Grom did very well up to 50 factory stock. If this is close to that then I just need to massage another 10 mph. The roads I travel are mostly 45. There are a few places where it is 55 and they aren’t flat. I want to be able to run those few 5 mile stretches at 60. I can’t pretend to know how to do that yet but I hope to figure that out. A ported head isn’t out of the question but I want to keep the stock piston for longevity.

 

[69ST]

Thanks for the input. If I recall my Grom did very well up to 50 factory stock. If this is close to that then I just need to massage another 10 mph. The roads I travel are mostly 45. There are a few places where it is 55 and they aren’t flat. I want to be able to run those few 5 mile stretches at 60. I can’t pretend to know how to do that yet but I hope to figure that out. A ported head isn’t out of the question but I want to keep the stock piston for longevity.

Again, I am unfamiliar with your local road situation. If they're mostly flat, you should be able to get those numbers without opening the engine. The biggest restriction one these bikes seems to be gearing; they are seriously over-geared and that has been addressed time & again since the first Grom reached US shores. Next up is the airbox, followed by the exhaust. Those are what might be termed "free" power adders, I consider them just optimal tuning and that's where I'd begin. Honda did everyone a big favor, designing these as "unstressed" engines, in stock form. That just means that they can be run WOT without hurting parts. See what you can pull out of the stock motor. These are 65mph bikes, motor left unmolested.

I would point out that if your Grom could only manage 50mph where you ride, you're going to need another 5-6hp to reach & sustain 60mph. You're giving me the impression that you need a lot more torque than is possible from a stock stroke.

 

[Clayton]

This is all great info, I have a 2020 Monkey that I have been wondering what I could do to get just a little more out of it. I rode my buddies 2020 Grom and honestly it seemed a little more peppy than my Monkey. I’m not sure if it really was or if it was just in my head lol.

 

[Deoodles]

I have owned both. The Grom might have a smidge more pep from the ecm tune. The Monkey is a better bike I’ve been doing a ton of research and don’t want to over do any upgrades. I like it stock but it needs a little more pep. So far I’ve gone from 15 to 14t on the front sprocket. It feels better. Also picked up a Takegawa SP exhaust and a speedometer healer. Intake and cam should get me where I want to be after the ecm flash. Still researching those 2

 

[Deoodles]

All parts ordered.
Takegawa SP exhaust
Chirmera short intake
TB cam
Speedometer healer for the gear change.

I’ve been talking with vendors from that world. DynoJet results put approx Hp around 12+. Gains start around 6k rpms. I am going to be receiving an ecm that learns and auto tunes

• Self mapping 0-100% throttle to target -
  
  • 14.2-14.8 idle AFR Target
    
    
  • 13.6-14.1 cruising for better fuel economy
    
    
  • 12.8-13.2 wide open for optimal performance
    
    
    As soon as I have time I’ll put this together and report back.

 

[69ST]

All parts ordered.
Takegawa SP exhaust
Chirmera short intake
TB cam
Speedometer healer for the gear change.

I’ve been talking with vendors from that world. DynoJet results put approx Hp around 12+. Gains start around 6k rpms. I am going to be receiving an ecm that learns and auto tunes

• Self mapping 0-100% throttle to target -
  • 14.2-14.8 idle AFR Target
    
    
  • 13.6-14.1 cruising for better fuel economy
    
    
  • 12.8-13.2 wide open for optimal performance
    
    
    As soon as I have time I’ll put this together and report back.

This is all very much what I was talking about. The hp & A:F numbers, look dead-on to me. With the exception of WOT, those are almost exactly what I see with properly sized & jetted carburetors. With a carburetor, varying fuel formulas and ambient air temps require going about .2-.3 richer, as established in high (ideally ~85F) ambient air temp, to cover the range of operating temps.

Tweaking all of the various fuel & ignition maps used to be incredibly time-consuming and you really had to know what you're doing. Replicating what a carburetor does, as airflow changes at every load, rpm & throttle opening combination, digitally...via maps...is more complicated than one might imagine. FYI, the MSX125/Grom EFI system was alpha-N, throttle position & rpm...as basic as EFI gets and decidedly user-unfriendly. (Dunno if Honda still uses it, or has upgraded.) That was a serious sticking point, for tuners. Since the cost of wideband O2 sensors has come down, self-learning & full closed-loop, operation becomes practical. A system with those capabilities combines the self-compensating aspect of a carburetor, then does the "jetting" for you...the best of both.

 

[Deoodles]

Speedometer healer installed. It’s great. Plug and play. I set it up in under 5 minutes. I mounted gps to the handlebars and verified my correction is 100% accurate in speed display and odometer. The fuel gauge started flashing at 160 miles. It took 1.06 of a gallon. Yup. 150 miles a gallon and a 1.5 gallon tank. I’m impressed with that. With the 14t sprocket it does 50 in 3rd gear below the rev limiter. Looking forward to the mods when the arrive.

 

[Clayton]

Could you post your part numbers for the sprocket and speedometer healer? I would love to do some minor upgrades to my Monkey to get a little more out of it.

 

[Deoodles]

Happy to do that. This won’t get you more speed but in my area with some hills; changing to 14t has made a big difference. I can take hills at 45 and be at 50 when I get to the top. It makes all 45 mph roads okay to be on. It will get you into the 50’s on flat roads easily. There is a power band that it likes in the low 40’s in 3rd and above 45 in 4th I’ve been learning how to mod CT70’s for many years and it applies to these bikes as well. They are factory over geared and the 14t is where it should be. The 12oclock labs calculator I used was helpful but it wasn’t exact. I imagine the stock setup had a +/- error in the speedometer display from the factory. My correction was 09.0 not 09.1 as the calculator stated. Dr ATV for the sprocket and Hardracing for the speedometer corrector. Shop around you may find better prices. I didn’t need a 14t. I had some from working on my CT70 gearing.

 

[Clayton]

Awesome!! Thanks for the info

 

[69ST]

Speedo error is all but impossible to eliminate completely. That applies to all vehicles, always has. Consumer GPS isn't as reliable as most think. FCC regs require a certain amount of error. Tower location, signal quality, device refresh rate and system latency can and do result in substantial inaccuracy. With acceleration & deceleration, GPS can be seriously ham-fisted. Over a long distance and with more or less constant speeds, it's pretty good; any spikes/dips in the readings will be easy to spot. A user-programmable speedo (which is what you now have) can be more accurate and far more responsive...as long as your measurements & math are spot-on. The Achilles Heel is treadwear, it decreases rolling circumference and every vehicle manufacturer has dealt with this from the get-go. I've used electronic speedometers that are calibrated in millimeters, which I've always considered over-the-top. Working in percentages, as you're doing, still gets you to within 0.1%. Cutting to the chase, the most extreme treadwear I've seen is with Trailwings...a little over 5% is possible, new-to-bald. I always replaced them when treadwear was in the range corresponding to 3-3.5%, which is close to what you'll have with road tires. The point of these ramblings, know the accuracy window and variables going in...then you get to choose where the input error comes in.

150mpg is beyond impressive. I got in on the ground floor of the Grom scene, watched the aftermarket parts appear & noted the results, never saw anyone reach that number. Honda must have made some big strides in efficiency. Your speeds are as expected...and virtually identical to what I get from my Nice-powered red bike. Not really surprising as Honda is consistent in their tunings/performance goals. Once you have the rest of your tuning parts installed & dialed-in, you should realize a good 10-12% beyond what I'm running...those extra CCs making themselves known.

And, yes...tuning is basically the same for any of these bikes. That's why I stick with the principles. Once you understand them, tuning becomes a logical, straightforward, process.

 

[Deoodles]

I couldn’t wait for the weekend but Friday night is technically the weekend. I installed all parts and the ecu. It has a nice low growl Can’t wait to take it out.

the exhaust still looks stock. It wouldn’t support a 183 build but I’m not doing that. It eliminated the cat and I gained almost 3” clearance. As you can see I eliminated almost 2’ of plumbing and almost 5#

The Cam has higher and longer lobes. It was as easy as a cam swap on a CT70 New cam on the right

The intake eliminated the black lunch box. I tucked it in under the tank. There were options for where it installed

Here it is all done. It won’t cruise at 65 but it will pull past 55 up hill. I can ride 55mph Roads for a few miles. That’s good enough. I’m actually done with the mods. I like all the things that folks remove like signals,taillight, trim. It looks great to me and it’s fast enough for these roads. Couldn’t be happier.

 

[Deoodles]

Real ride report. I did 50 miles on it today. I’m happy to report it can pull 60mph up hill but in 3rd. If I shift it falls flat in 4th. The exhaust is great and worth the cost. The cam is also worth the cost lots of high rpm power but I guess I’m still geared too tall for 4th. I am not so sure I like the intake. It is quite loud and sounds like a P-51 mustang propeller when I twist the throttle. I think I have to give it a thumbs down. My ecm self tunes so I may go back to the stock air box and see how it performs. I have more than enough performance so giving up 1hp may be acceptable. On the fence for now. I would tell anyone don’t upgrade the air box if you don’t like noise.

 

[69ST]

That's all in line with expectations. I don't like induction noise either. With the inlet in this location it's got to be even more annoying than on a CT.

Once you start covering some real mileage, seemingly little things become not-so-little. And you're at the stage where 100 miles can go by like nothing.

 

[mark from florida]

I think youll achieve your goals with the listed upgrades. I have a stock bore grom with a full yoshi exhaust knn intake and a retuned ecm also a tb cam. the cam really woke it up. my top end is around 73-4 at wide open. will cruise at 55 -60 pretty good. power off the line will surprise most drivers. will feel like a total different bike with just a few mods. enjoy