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2018 Honda Monkey
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Discussion Starter #21
To remove the OEM crank bearing from the case I used 2 sockets and a cup head screw. The cup head screw locked into the 1/2 drive on the socket, so I could tighten the socket down against the inner race of the bearing. I then put a much larger socket over the smaller socket, so there was a large flat surface. I then gave it a few careful hits with a mallet to pop out the old bearing.

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To get the new crank bearing in, I froze the bearing and heated up the case. Even after doing that, the bearing only slid in half way before getting stuck. To get it all the way in, I put the old bearing on top of it, and used a socket on the inside of the bearings as a locating pin. I then carefully tapped the outer race of the old bearing, working my way around the perimeter until the bearing was fully seated.
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When it was time to install the crank, the heat and freeze method didn't work at all. Tbh, the only good way of installing the crank into the case half is with the proper crank puller tool. Luckily I have a local Kitaco/Takegawa importer who had the tool in stock.
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A few of tips for anyone doing this:
  • Buy a box of resealable sandwich bags and a sharpie. As you disassemble the engine, label the bags and group the components
  • Take lots of pictures, especially the order that things sit on the crank and transmission input shaft
  • When you split the cases, use 2 rubber bands to stop the transmission falling out
  • Lookup Honda Grom Parts Fiche before you start to disassemble the engine. Make note of small dowel pins.
  • The engine can stand up on its own if you use M8 bolts and washers in the 4 holes on the bottom of the motor
 

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2018 Honda Monkey
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103 Posts
Discussion Starter #23 (Edited)
For the throttle body, I'm using a 34mm Honda Vario scooter throttle body. At 35usd, it's a steal and shipping from China to Aus is much cheaper than USA to Aus. You'll need the koso manifold to fit it, but I got one of those really cheap from a friend that bought a gf rev wedge.

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Already comes ported and polished

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Sensors are the same as the monkey/grom

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Weirdly enough, the new throttle has the same bolt spacing as the stock throttle, so I had to modify the koso manifold to fit. Bolt holes were reamed out, the top corner was notched in to make room for the iacv, and the side was ground down slightly to make room for the return spring. Also, the cable guide plate from the stock throttle can be swapped onto the vario throttle to retain the oem cable protector plastic.

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Yes it comes with the infamous brass screw

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Since I had bought the koso manifold second hand, I had to bore out my stock insulator and find a new injector seal ring. I ended up with a Nissan SR20/RB26 injector seal

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2018 Honda Monkey
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Discussion Starter #24 (Edited)
Next issue is my injector woes. With my old pcx150 injector, it would fire up straight away and throttle response was great. The issue was that the duty cycle was above 85% from 8500rpm and above. At 11300rpm, the duty cycle was 100%.

I've ordered the Forza injector 235ccm from Honda, but it's on backorder due to the Covid situation. Until it gets here, I've got a 180ccm 14 hole yuminashi injector that someone was using for an E85 grom.

The bigger injector is giving me some tuning headaches. Cranking fuel had to be turned way down, since it was fouling plugs on startup. I'm still experimenting with throttle tip in enrichment. My in gear enrichment is now working well, but the neutral/clutch in enrichment is still too rich. A sharp crack of the throttle will stall the bike in neutral. This is actually kinda dangerous when rev matching on downshifts. Main table fuelling is easy to tune with the wideband, but these finicky bits like warmup, cranking and tip in are just trial and error.

For spark timing, I'm using gsx/jc's timing table and it flat out rips. The pv3 was artificially limiting the spark timing at first but now I've changed the limiters to allow 27 degrees btdc at high rpm and 100% throttle
 

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One other thing to note is that the maximum negative long term fuel trim is 36% on the stock ecu, so installing a PCX injector (56% more flow than stock) will make your map ~20% richer.
So for people with a stock bore running an exhaust and intake with NO fuel controller, to prevent running lean or too rich at WOT they would be better running this 120cc injector instead of the 140cc injector you ran?

 

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Discussion Starter #27
So for people with a stock bore running an exhaust and intake with NO fuel controller, to prevent running lean or too rich at WOT they would be better running this 120cc injector instead of the 140cc injector you ran?
Yeah that's right. There's another Sydney rider who uses that injector. The 120 is good, but the 140 is cheap and readily available from Honda.

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Discussion Starter #28
Next upgrade is an Over Racing Exhaust. Webike has them on sale for 17% off today.

One of my other monkey buddies has the Ti version of this pipe, and it has a nice large header (28mm at the flange and tapers up). The SS version that I'm getting should be the same size, but I'll report back once I get it.
 

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Discussion Starter #30 (Edited)
I've upgraded the ignition coil to an aRacer Power Spark Red. It has adjustable spark energy levels (1-9) which is kinda reassuring when you're so far from stock. It says to use 1-9 for stock motor, 1-6 for a 155cc big bore and 1-4 for a high comp motor. I've got it set at 3 at the moment and it seems to be working.

Not sure if this is helping up top. The bike runs out of puff at 10500rpm. Not sure if its held back by the 10d cam, the standard porting or my tiny exhaust (still haven't received my Over Racing pipe). I did notice that the idle is a bit more stable and its a bit cleaner off the bottom. I guess thats a win?

It bolts up fine on the stock coil mounting holes, but the terminals end up the opposite way around vs the stock coil, so make sure you check the connectors if you;re installing one of these
 

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103 Posts
Discussion Starter #31 (Edited)
When I initially built the 4v, I used the spring loaded tensioner rod since I installed a new reinforced cam chain. I didn't want to have to adjust a manual tensioner until the new chain had done its initial stretch (yes I'm lazy). Now that the 4v setup has ~750km, the cam chain should have settled in and I've installed my yuminashi manual tensioner. The price and quality seem pretty good, but there's legit no instructions on what slack to adjust to.

To set it up, I tightened it until the tensioner wheel until it was fully in contact with the chain, then backed it off half a turn. I then started up the bike, and listened to it using a flathead screwdriver. Put the flat head of the screwdriver firmly against the motor (I did this at a stator cover bolt, the cam cover bolt and between 2 cylinder fins) and put your ear against the handle of the screwdriver. It works as a crude mechanics stethoscope. I adjusted the screw in/out a turn to the point it was quietest. Using the screwdriver stethoscope, too tight and you can hear whining, too loose and you can hear chattering of the (koso) tensioner wheel.

One weird observation is that the valve ticking is a lot louder after setting the tension manually. Could be that the better tensioning of the chain is forcing the valves to open better, and that the spring loaded tensioner was flopping back and forth as it hit the ramp up on the cam lobe.

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Discussion Starter #32
Takegawa z50 catch can installed. Actually looks ok on the monkey. I tried running a car catch can for a bit. It did the job, but I could never get it to sit right because the spigots were all in the wrong spot. The takegawa can fits perfectly and bolts onto the unused bracket used for the USDM charcoal canister. I've got it set up with the front 5/16" spigot venting to atmosphere with a breather filter, the back 5/16" to the stock crank breather, the side 1/4" (hidden in the picture) to the taky 4v head breather and the 1/2" bottom spigot to the oil filler cap.

Overall, I'm happy with it, but I think I'll swap to black nylon braided lines in the future. The tubing looks a bit meh, especially the clear return hose.

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Discussion Starter #33
One of the Sydney guys needed a chimera, so I sold it off and used it as an excuse to get something bigger for the new throttle body. While waiting on postage, I was running a spare filter direct on the throttle body and it ran like dog shit.

The new intake is much bigger and better. The velocity stack is actually made for a car with 1 carby barrel per cylinder. The filter sock has a large diameter spring which sits on the vstack to maintain clearance.
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Discussion Starter #34
New Dproject stainless steel axles and swingarm pivot installed. They are double nutted and also have a small locking screw on the end that hides the end of the nut and axle

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I really like that locking screw. I have had a swingarm pivot nut come loose once. Where did you purchase them?
 

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Discussion Starter #36
I really like that locking screw. I have had a swingarm pivot nut come loose once. Where did you purchase them?
They're from Dproject in Thailand. Look them up. You have to chat with them on Facebook for the axles/pivot since their website doesn't have it. They mainly do rims.

One of the other Sydney monkeys has Dproject rims with a 6" wide rear on his monkey. He ordered the axles fore since he's talked to those guys a fair bit

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Discussion Starter #37
The Takegawa 4v has amazing midrange power, but I'm looking for a little bit more. The top end is held back by the port size and the cam. I think porting may be a 2021 job for me, but I have been sorting out the cam over the last few weeks. Takegawa does make an optional cam (15d) for the 4v which is supposed to increase top end, but it's not really much of an improvement. The total duration and peak lift of the 10d and 15d cams are the same. The difference is in the ramp up rate of the cam and (maybe?) the lobe centre spacing.

Me and another forum member are getting custom 4v cams made up, but doing it different to compare results. He sent his 10d to Web Camshafts, but since I'm in Australia, I bought a 15d cam from HardRacing and had them ship it direct to Daniel Crower Racing (saves shipping cost and keeps my bike on the road while its getting done). By the looks of things, the Web Cam might end up a bit crazier than my DCR cam, but Dan was awesome to deal with as an international customer and offered good value for money. He's reground my cam for more lift and duration, while keeping the takegawa decomp mechanism intact. I'll have some feedback on the performance over the next few days.

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Nice, keep the updates coming. Might have to start a thread for my 143 build 😁
 

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GSX on this forum had a cam made for the Take 4V. Not sure it was DCR or someone else though.
 
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