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Discussion Starter #1 (Edited)
Alright I decided to make a Build thread for my grom.

Main Objective: Function Over Form
Main Use: An around town / camping / small trail bike

Backstory:

When the grom first came out i knew i wanted one so it was only a matter of time. A little before xmas 2015 I had been watching this used grom local to me drop in price and when he finally dropped to 3k for the 2014 grom w/ 3800 miles i jumped on it. (Groms down here in so cal go for a pretty penny). It came with a hot bodies fender eliminator / integrated turn signals, chimera intake / K n N filter, and Full Yosh RS9. It also came with ALL of the stock parts (airbox, exhaust, rear fender, etc) as well as the fuel pump recall done and TONS of maintenance logs, the previous owner did a good job.


The Build

I rode it around for a bit and quickly realized a few things. No fender SUCKED for the riding I did in the dirt / mud, Also the yosh rs9... while nice, was WAY to bloody loud for my likes. Very quickly i popped the stock rear fender back on, as well as the stock exhaust. OH so much better, i could hear myself think while riding it and not get dirt / mud / water sprayed all over my back when doing so.

Then The mod bug hit.... I couldnt care less about how it looks, everything i have done is to increase functionality in some way.... eff fancy flashy stuff, lowering kits, bar end mirrors etc etc. My build is all about bring better performance / functionality in a 100% reliable package that i didnt have to worry about tuning / dealing with different tunes.... i want it to just work. I have been through a few phases of this build but I am at what i like to call my "final product" So here are the list of things done to her.

Engine:

  • Non BBK Related
  • BBK TIME!
    • Kitaco 164cc BBK (chose this as much bigger than 60mm bore you get into possible headgasket issues... remember reliability is HUGE for me)
    • Finbro ECU with my http://www.hondagrom.net/forums/49-grom-how-s-guides/10482-finbro-cold-starting-fix.html
    • Finbro 6 Hole injector (CBR150R injector)
    • Custom nylon cam chain tensioner button (a nylon bolt filed down to the right size) - Now been replaced with a finbro nylon button because it was sent with my CCT
    • Kitaco type 1 cam (chose this because it was going to produce more power in the low to mid range vs high end which is better for my uses) - Now been replaced with a Kitaco Type 2 cam with stock decomp moved over
    • Finbro Upgraded stiffer valve springs
    • A big 5 row oil cooler from ebay Mounted from the frame with custom brackets i made (This is one of the biggest i have seen fitted to a grom, and it also has a nice plastic guard so it doesnt get punctured)
    • A DG header to get rid of the stock real restrictive header, BUT keep the stock exhaust can to keep it quiet!
Non Engine Rleated


Overall I am SUPER happy with the power and ride now. Its turn key go, no dealing with a pcv / bazzaz for tunes, just let the finbro ecu do its thing. It makes GREAT power, i can now cruise at 55-60mph and still have throttle left to grab, but also have power down low for bigger slower speed hill climbs in the dirt. I gained ground clearance with the header and fork mod, and traction with the dual sport tires. I cant wait to put some miles on her now as of writing this it has maybe 100 miles on the bbk, but i have been mean and broken it in like a red headed step child.

Questions / Comments, feel free to ask!


Edit - 12.11.16
- Changed cam chain tensioner to finbro upgraded unit, Changed to kitaco type 2 cam with a stock decomp mechanism.

Edit - 11.22.17 - Upgraded head!

Alright, so i FINALLY got her all together like i should have the first time. That is with a bigger valved head. I went with the finbro superhead (27/23mm valve) from franco for 250 bucks. Had i known i could of gotten the 28/24mm valve head from monkey father for 270 bucks... i would of gone that route. But i am happy with the results of the superhead (that definietly needed some work - see here http://www.hondagrom.net/forums/7-grom-talk/35866-finbro-superhead-quality-meh.html) as well as some throttle body and intake manifold work to port match everything (see here- http://www.hondagrom.net/forums/7-grom-talk/36018-throttle-body-mod.html)

She is finally properly rev happy and doesnt fall on her face at 7k rpms like before with the tiny valve n port stock head. I had to get headgaskets from webike directly, 30 bucks for 2 of them shipped which wasnt bad. Upon disassembly i cleaned up the top of the piston / combustion chamber and top of the head and quickly remembered why i was happy with the kitaco bbk. Damn the machining on the piston and top deck of the cylinder are beautiful. Overall with the smoothing of the combustion chamber dropping compression a smidge (something i actually wanted) and more flow through the head, it runs cooler and stronger! All win win win.


Edit - 12.08.17
Decided i wanted more clutch grip, so a billet clutch plate, 6 much stiffer finbro springs, and tapped the other 3 standoffs for a 6 bolt clutch setup - check it -> http://www.hondagrom.net/forums/7-grom-talk/36505-nd4-s-bulletproof-clutch-mod.html#post402441
 

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Discussion Starter #2 (Edited)
Reserved for future pics / media

06-24-16 After work short ride in the dirt, climbs hills SOOOOOO much better now with the bbk, i can lug it at 3k rpms and pull HARD before id have to REALLY work the clutch to keep it in power.






08-06-2016

Finally getting to going through the pics of my recent trip to mammoth, did about 120 miles on the grom, most of which was off road!

















 

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Looks really good. Did you go with the cbr injector after the pcx injector? Or went from oem to cbr? What did you need to install it?
I have the pcx and i'm planning to go to the cbr but i don't know if its necessary or not...
 

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Discussion Starter #4
Looks really good. Did you go with the cbr injector after the pcx injector? Or went from oem to cbr? What did you need to install it?
I have the pcx and i'm planning to go to the cbr but i don't know if its necessary or not...

I ran the PCX injector when i was on stock bore with a cam and the finbro ecu. I thought i could get away with the pcx injector with the 164cc bbk, but alas, i needed one notch bigger as i was lean with the pcx and 164cc. So i contacted franco at finbrogarage and after a month or so he got a batch from monkey father. The CBR150R aka "Finbro 6 Hole keihin injector" from franco comes not only with the injector, but necessary orings on the injector, new injector cap (same as the stock cap, but its been drilled out to accept the larger diameter injector top), 2 little spacers (as the cbr injector is taller), and the small little wiring harness so its all plug and play (cbr injector has a slightly different plug compared to the stock injector).


Id say the PCX injector with the finrbo ecu would be good to ~ 143cc bbk.
 

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I ran the PCX injector when i was on stock bore with a cam and the finbro ecu. I thought i could get away with the pcx injector with the 164cc bbk, but alas, i needed one notch bigger as i was lean with the pcx and 164cc. So i contacted franco at finbrogarage and after a month or so he got a batch from monkey father. The CBR150R aka "Finbro 6 Hole keihin injector" from franco comes not only with the injector, but necessary orings on the injector, new injector cap (same as the stock cap, but its been drilled out to accept the larger diameter injector top), 2 little spacers (as the cbr injector is taller), and the small little wiring harness so its all plug and play (cbr injector has a slightly different plug compared to the stock injector).


Id say the PCX injector with the finrbo ecu would be good to ~ 143cc bbk.
Thanks! I'll give it a try! Does only sell it finbrogarage? I'm located in spain...
 

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Good job! I like that you had reliability in mind.
I'm hoping to do similar mods as you have.

What is your top end like?
 

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Discussion Starter #9
Good job! I like that you had reliability in mind.
I'm hoping to do similar mods as you have.

What is your top end like?

Top end as in top end power? or top end as in top end (head / intake / valve) setup?

Top end power is good, FAR FAR better than stock, before i would struggle to do 55. Now its a breeze. I actually was able to do 70mph indicated on the speedo (around 63-64 actual due to my gearing). I will say the stock head and or stock throttle body seems to be a limiting factor in willingness to rev past ~8.5k rpms. Its just alot of air to flow through the stock TB / head and you can tell that if you wanted to rev more opening up at least the TB would do some good. For me, its fine, if i want more top end speed ill go back to the stock 15/34... but the 15/37 im currently rocking is SO MUCH FUN around town and in the dirt.
 

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Top end as in top end power? or top end as in top end (head / intake / valve) setup?

Top end power is good, FAR FAR better than stock, before i would struggle to do 55. Now its a breeze. I actually was able to do 70mph indicated on the speedo (around 63-64 actual due to my gearing). I will say the stock head and or stock throttle body seems to be a limiting factor in willingness to rev past ~8.5k rpms. Its just alot of air to flow through the stock TB / head and you can tell that if you wanted to rev more opening up at least the TB would do some good. For me, its fine, if i want more top end speed ill go back to the stock 15/34... but the 15/37 im currently rocking is SO MUCH FUN around town and in the dirt.
Yeah I was thinking speed haha sorry.
I'm looking for a little top end speed so IF I need to hop on the freeway, I could do so (for short distances).
 

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Discussion Starter #11
Yeah I was thinking speed haha sorry.
I'm looking for a little top end speed so IF I need to hop on the freeway, I could do so (for short distances).

Oh yeah, with this setup if i went back to the 34 tooth rear sprocket i could hang at okish highway speeds (60-65) on flat ground without being WOT full tuck drafting a car.
 

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How do you like the tires? Do they perform well off-roading? I want the Maxxis tires but I do more committing/highway driving than I would off-road but would to be able to take it in the sand and dirt without it slipping around on me
 

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Discussion Starter #13
How do you like the tires? Do they perform well off-roading? I want the Maxxis tires but I do more committing/highway driving than I would off-road but would to be able to take it in the sand and dirt without it slipping around on me

Obviously the tires do not do as well as something like the M6024, but the Kenda K761's do a DAMN good job off road, MUCH MUCH better than any street tire, but they still have great grip / road manners on road. I would recommend to mount the front tire "backwards" from the rotational mark so its tread pattern is proper.

Overall i have been very happy with the kenda's, no regrets with going with those, and they are pretty quiet on the road too... i cant imagine how loud the M6024's would be.
 

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Discussion Starter #14 (Edited)
Whelp I have put ~ 200 miles on the bbk so it was time to do its first oil change. Expecting the worst of rubber chunks from the cam chain guides and tons of metal shavings, then hoping for the best at the same time.

Oil came out with just a lil glisten of break in metals, no chunks of anything. Valves were still spot on, my nylon cam chain button made out of a 30cent nylon bolt from the hardware store was still in tact.

Oil screen had one ITTY BITTY piece of metal on it (looks like an aluminum scraping probably from the wrist pin clip when i put that in) but NOTHING more! A lil bit o gunk / particles inside the oil spinner.


All in all, your standard amount of stuff for a new cylinder piston etc, SUPER HAPPY. Filled her back up with some Rotella T6 5w-40 and went on a 30 mile ride. Thing is a god damn hoot!
 

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What kind of mpg do you think or know you are getting now vs a stock 125 engine?
Is the low end grunt now a lot more so wheelies are easier in 2nd or 3rd if you do wheelies.
how many miles now on the bore setup?
 

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Discussion Starter #20
What kind of mpg do you think or know you are getting now vs a stock 125 engine?
Is the low end grunt now a lot more so wheelies are easier in 2nd or 3rd if you do wheelies.
how many miles now on the bore setup?

Honestly never tracked my MPG's but its not significantly worse than stock by much if any at all.

Low end grunt is MUUUUCH improved. Power wheelies in 1st are stupid easy, and you can actually bring it up in second now. The low end is DEFINITELY seen off road when im slow going in 1st, I have the ability to pull out of first gear on steep climbs where before there was nothing left that the motor could give.

About the only real thing i would do different would be to run two base gaskets to reduce the compression a smidge.

I am playing with the idea of running a bigger valve head as the stock head doesnt flow much past 8k rpms with the 164cc bbk. Or try out a more aggressive cam to let it breathe better. Kind of torn there to be honest... Part of me wants to keep the stock head as parts availability for the stock valves / head etc are easy to come by, and i wouldnt have to source a new headgasket / tear the motor apart for a different head.


Miles wise.... i think i put the bbk on at ~4400 miles, and i now have 5100 on the bike. so ~700 miles, I will have to check my logs when i get home as i am curious as well to see how many miles i got on the thing!
 
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