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Discussion Starter #1 (Edited)
Nectar's Koso 170 4V Build

Hi All, this thread documents my 2015 build that I started in December of 2017. I bought it with 700 on the clock, with a few mods like a slip on, flushmounts, and some other cosmetic upgrades. I normally do a poor job of document my bike builds and always end up regretting it, so I'm hoping this thread will motivate me to do a better job.

I used to own a Ruckus in college and was active on TR, so I knew that the Grom was quickly about to turn expensive even before getting one. After my Ruckus, I got into sportbikes before finally obeying the n+1 rule after a few years post college.

I commute daily and ride for sport on weekends, so I mod my bikes pretty extensively. I don't own a car either, so I have that extra bit of naughty justification in my head that is just downright dangerous when shopping for Grom parts.

Since I picked up the bike, I've added quite a bit to the component list. My goal is to have a solid, stable sport platform. I know I want more power, but I'm going to try to get to 5k on the stock motor before I go crazy.

Here's how the bike currently sits:

2015 Honda Grom (25XX miles)

Engine/Powertrain
Yoshimura RS-9 w/ MNNTHBX header
Chimera Intake w/ Sprint Filter
TB Camshaft
Dobeck EJK
PBI 36T sprocket
EBC Clutch Springs
Hard Racing Engine Brace
Hard Racing Shift Spindle Support

Suspension/Controls
Racing Bros Front Fork Kit (Preload/Comp/Rebound adjustable)
Racing Bros Shicane HLR Shock (Preload/Comp (hi/lo)/Rebound adjustable)
Composimo Racebarz
Driven Racing TT Rearsets

Misc
Michelin PP (140 rear)
AEM A/F Gauge w/ Wideband O2 sensor
CRG Blindsight bar end mirror
MNNTHBX Faux Frame
Tyga Lower Cowl
Renthal Grips
Techspec Gripster Tank Grips
Shorty Levers

And now for the pictures...















 

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Discussion Starter #2 (Edited)
Big changes in the pipeline for this Grom. The need for speed was too great, so another Koso 4V build was born. Parts arriving this week, teardown already started.


Aracer Mini Plus 2 ECU
Koso 170 BBK w/ 4V head
Koso 34mm Throttle Body
Keihin 10-hole injector
Koso Cam Chain Tensioner Arm
Kitaco Clutch Cover
Takegawa Super Oil Pump
eBay External Oil Cooler
Takegawa 4th Bearing
OTB Cam Cover



The fun begins.



Pretty uneventful teardown. Is this a lot of carbon buildup for a piston?



Piston has since been removed. Engine is ready for the BBK install tomorrow.
 

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Make sure you get the 4 into 1 cable for the Aracer mini2+ since you should get the AF1 "autotune" and DG1 "A/F gauge" it will make life a lot EZ when tuning.

Also a good oil catch unit so to reduce Crank Case Pressure and Heat, best system would be a closed loop circuit with the a pressure release thru the airbox and oil return to the oil spout filler hold and intake valve cover.
 

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Discussion Starter #4
@Cisco, I was planning on doing the GY6 crankcase breather, that has the 1/2" ID tubing coming out of the oil filler cap with a K&N Attached. I was then just also going to put a push in K&N on the factory breather. I will see how well this works at first.
 

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Nice build 'nectar.

Let me know how the Koso 4V goes. I am leaning that way myself. Then I lean to the NEO side. I just wobble too much I guess.


Pics of your catch can set up please. You say you are using parts from a Ruckus? Oh the horror... LOL
 

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Discussion Starter #6 (Edited)
@WV Grom

I am following chaddington's guide here: http://www.hondagrom.net/forums/49-grom-how-s-guides/19258-big-bore-crank-case-breather.html

The GY6 vent hose kit he recommends has a nice large 7/16" ID, which seems to be the key to effective/sufficient venting. I plan on using a UNI push in filter on the stock crank breather hose as well (the one that normally terminates at your intake). Ideally, I would've gone for a catch can setup, but after all those BBK parts, money's tight for now. It seems like the DIY catch can setups are too restrictive to be effective, and tailor-made catch cans for the Grom come at a cost of course.

I PM'd him right after I bought my BBK, his Koso 4V is still running strong to this day, so I decided to follow his advice :)

The Ruckus was the one that started it all for me...before the big bikes, there was my college commuter. I've officially gone full circle, back to buying Ruckus parts :lol:
 

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Discussion Starter #7 (Edited)
Just got my Koso BBK in...somehow I am MISSING the piston rings. this kit was sealed from Koso! WTF!!! the rings are definitely not there. welp...this WOULD happen to me.

edit: Am i correct in assuming the 61mm piston rings from the piston intended for the stock 2V head will work with the 4V piston?
 

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Discussion Starter #8
Well, we're $80 dollars deeper than yesterday. That could be a motto for this build lol.

I ordered a 61mm piston kit just for the rings. I assume the rings between the 4V and 2V head are the same. God that felt silly.
 

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I would recheck your original Koso 170-4v kit box that it came in, those rings are some times missed when throwing out the trash, and check the trash to make sure you did not accidentally dump the rings or the ring package wasn't tapped to the box cover.
 

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Discussion Starter #10
Checked it all, even took photos of the unboxing. Nothing in the trash either. Shit happens, must've been boxed up incorrectly :( Life goes on, parts on the way, fingers crossed its the only hiccup!
 

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Good luck on your build, make sure to get the mapping right 13.2 A/F across the RPM range and under 7K rpm on the first 500 miles break in and maybe 5K rpm might be safe.

My build 181-4v is at almost 2K miles on the engine and yes you can feel the difference in performance, it puts a smile on your face.
 

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My rings were in the little red plastic case the piston was in.

Cisco- “keep it under 7k for the first 500 Miles”?
Oops.. I took it up higher but only after ~175 miles. Hope she holds.
 

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My rings were in the little red plastic case the piston was in.

Cisco- “keep it under 7k for the first 500 Miles”?
Oops.. I took it up higher but only after ~175 miles. Hope she holds.
No problem there since you are breaking in the seal between the piston and the cylinder walls. Some people like to open it up to get a good seal right after installing a new engine. I have done the over 7K rpm with no danger. Maybe that is why this engine is running so great. I did have problem with blow by at first because I had rigged up the oil catch can return lines wrong which caused blow by in the engine causing the oil rings to go bad and it was funny I had no replacement rings so I took off the oil rings from my blown engine since the rings looked good with no scratches or scare and it is holding great.
 

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Discussion Starter #14 (Edited)
My rings were in the little red plastic case the piston was in.

Cisco- “keep it under 7k for the first 500 Miles”?
Oops.. I took it up higher but only after ~175 miles. Hope she holds.
My red piston box only came with the 4V piston and the wristpins and clips. I methodically unboxed the entire kit to take inventory before I started. I checked underneath the foam at the bottom of the box, nada. Hate to say...but Koso fucked up when they packaged this particular box.

In better news, Kitaco clutch cover, Takegawa 4th bearing and oil pump, and some other goodies should be arriving today, so the project can keep chugging along.
 

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In better news, Kitaco clutch cover, Takegawa 4th bearing and oil pump, and some other goodies should be arriving today, so the project can keep chugging along.
Man, that sucks about the piston rings. At least it's something small. I hope they work with you and just get you a set sent out.

Don't forget to drill the stator side cover for the 4th bearing so it can get oil... I didn't know about that until Johnny posted in my build thread. It isn't too bad to do though. Just one in the top side and you're good to go!

Glad to see another 4v 170 in the works... and remember, the Grom god's will shine upon you!
 

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Discussion Starter #16 (Edited)
Man, that sucks about the piston rings. At least it's something small. I hope they work with you and just get you a set sent out.

Don't forget to drill the stator side cover for the 4th bearing so it can get oil... I didn't know about that until Johnny posted in my build thread. It isn't too bad to do though. Just one in the top side and you're good to go!

Glad to see another 4v 170 in the works... and remember, the Grom god's will shine upon you!
I'll post whatever Koso's response is. I'm super impatient, so I already ordered the Koso 2V piston off eBay so I can harvest the rings. I got a great deal on the kit, so I'll chalk it up to bad luck.

If Koso does throw me a bone and help me out w/ new set o' rings, at least I'll have a complete 2V Koso piston to re-list and sell.

Thanks for the reminder to drill out the stator cover! Don't want that bearing going dry.
 

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Discussion Starter #17 (Edited)
Well, KOSO just said "The part # for the piston ring set is; ME000G6100. We don’t have it available on our website so you will most likely need to call to place the order." I guess that's to be expected. I didn't buy it from them or another vendor.

After talking to them, a set of rings is $62 shipped from Canada, should be here by Friday. Its $18 less than the new piston, so I went that route. Back on track...
 

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Discussion Starter #18
Man, that sucks about the piston rings. At least it's something small. I hope they work with you and just get you a set sent out.

Don't forget to drill the stator side cover for the 4th bearing so it can get oil... I didn't know about that until Johnny posted in my build thread. It isn't too bad to do though. Just one in the top side and you're good to go!

Glad to see another 4v 170 in the works... and remember, the Grom god's will shine upon you!
I'm having a bit of trouble figuring out how exactly I am going to drill the stator cover for the 4th bearing to receive oil. Got any tips? I have to seriously angle the drill to get clearance.

Go from the outside in, or the other way around? The space seems way too tight for my drill, maybe I need a much longer bit.
 

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I'm having a bit of trouble figuring out how exactly I am going to drill the stator cover for the 4th bearing to receive oil. Got any tips? I have to seriously angle the drill to get clearance.

Go from the outside in, or the other way around? The space seems way too tight for my drill, maybe I need a much longer bit.
This is what I used. I went to harbor freight and got a 90 degree drill bit adapter. It's plastic so it didn't mar up the case at all. I forgot what size drill bit exactly. I ended up using a porting tool at first but I think I could have done it all with a drill bit. Use a punch to make a divot facing from the top straight down. Then have at it! There's no easy way about it really.
 

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Discussion Starter #20
Thanks for the photos @phillybuilt.

Is the plastic chuck the *main* reason you used the 90deg adapter? My drill has a plastic chuck already, if that's the main reason that was used.

I'm going to pick up a center punch to try.
 
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