186cc BBK overheating issues. Help me Obi-Grom Kenobis

1852 Views 5 Replies 5 Participants Last post by CDN Grom, 21 d ago

azninja250

Discussion Starter · Sep 28, 2020

I recently bought TBParts 186cc BBK + oil cooler kit. But I'm running into temperature issues when testing the 2018 Honda Grom engine build out. It exceeds 240F to 260F under normal load no WOT. I've included the list of mods I have done and hoping anyone can direct me to what I've done wrong or opinions on how to keep engine temperatures under control.

Cold Air intake
TBParts 186 cc bbk w/ external 3 row oil cooler. TB 186cc Grom Big Bore Kit and Oil Cooler Kit - TBparts.com
Pcx 150 fuel injector.
DHM 186cc Flashed ECU DHM 186cc ECU Reflash Service (During cruising, DHM has set AFR to be mid 14s to save fuel. On deceleration the numbers will be very high 16+ since there is no fuel being added. You can look for 11-13 when WOT. )
Dual aftermarket exhaust
10w-30 Oil
NCY Oil decompression tube
Opid Gen 2 engine temp gauge (set to P-2 Grom setting)
NGK Cpr7eaix-9 spark plug
Koso mini 3 air/fuel ratio meter
Idle Set to about 1800
Koso Oil Pump
NGK 2-CR8E Spark Plug (whitish brown residue after ride)

Installed bbk by following Hard Racing's video found on YouTube.

Any ideas on whats causing this over heating issue outside of being in Arizona?

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pitasmit

· #2 · Sep 29, 2020

Talk to someone about enlarging the "oil jet". That controls the amount of oil flow through the cylinder. It's on page E-15 of the parts manual. Part 11133-KYZ-900 JET, OIL, 1.0MM •••••••••••••

See http://www.battle.co.jp/partslist/honda/grom/18k26gt1.pdf

IMO if you have high flow pump you can enlarge this jet to provide more flow through the head stud to your cylinder mounted oil cooler outlet.

I plan to do this - I have a 33% larger oil flow and hence the jet can be increased by 33% area (without a loss of pressure) which is 0.785mm sq to 1.05mm2. That mean drilling it out to 1.15mm.

The function of the oil jet is to build pressure in the oil system.

I can't find a lot of info on this and am surprised that no one is talking about this but as an engineer I see no issue with it. There is some thought that needs to be put into whether there are other jets in the system. I need to check the lubrication pathways in the service manual later.

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Chillis

· #3 · Dec 24, 2020

azninja250 said:
I recently bought TBParts 186cc BBK + oil cooler kit. But I'm running into temperature issues when testing the 2018 Honda Grom engine build out. It exceeds 240F to 260F under normal load no WOT. I've included the list of mods I have done and hoping anyone can direct me to what I've done wrong or opinions on how to keep engine temperatures under control.

Cold Air intake
TBParts 186 cc bbk w/ external 3 row oil cooler. TB 186cc Grom Big Bore Kit and Oil Cooler Kit - TBparts.com
Pcx 150 fuel injector.
DHM 186cc Flashed ECU DHM 186cc ECU Reflash Service (During cruising, DHM has set AFR to be mid 14s to save fuel. On deceleration the numbers will be very high 16+ since there is no fuel being added. You can look for 11-13 when WOT. )
Dual aftermarket exhaust
10w-30 Oil
NCY Oil decompression tube
Opid Gen 2 engine temp gauge (set to P-2 Grom setting)
NGK Cpr7eaix-9 spark plug
Koso mini 3 air/fuel ratio meter
Idle Set to about 1800
Koso Oil Pump
NGK 2-CR8E Spark Plug (whitish brown residue after ride)

Installed bbk by following Hard Racing's video found on YouTube.

Any ideas on whats causing this over heating issue outside of being in Arizona?

Curious if you figured out your issue?

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boingk

· #4 · Jan 14, 2021

Old thread but this stood out to me:

DHM has set AFR to be mid 14s to save fuel

I'd say thats the issue right there. Back it off to 14 flat and see how the temps go. You won't lose a ton of MPG but the temps should be much better.

A true stoichiometric ratio always burns much hotter than a slightly richer one, and the added benefit of slightly more cooling fuel in the cylinder helps as well.

- boingk

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Chillis

· #5 · Jan 15, 2021

boingk said:
Old thread but this stood out to me:

I'd say thats the issue right there. Back it off to 14 flat and see how the temps go. You won't lose a ton of MPG but the temps should be much better.

A true stoichiometric ratio always burns much hotter than a slightly richer one, and the added benefit of slightly more cooling fuel in the cylinder helps as well.

- boingk

Most of the aftermarket companies have the AFR around 13 to 13.5.

I'm curious to see what type of gas mileage dip I will get after the 4 valve conversion with ported head/manifold.

Even though the bike will be able to go much faster I still plan on taking it easy on the road. Trying to stick to maybe 65 mph as a max cruise speed.

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CDN Grom

· #6 · 21 d ago

So, because I was researching 186 BBKs and came across this thread, I reached out to @azninja250 to see if they ever sorted out the issue and got the following reply: "It turned out my temp/voltage gauge (Opmid OPMID "Version 2.0" M1011 M1013 Engine/Head Temperature Gauge w/ Voltmeter (Plug-n-Play) GEN2- '13-'20 Honda Grom / Grom SF ) was known for misreading 20-30 degrees on groms.

I found multiple forum posts like this ( OPMID temp issue or something else.. ) Where people had issues with Opmid plug and play temp sensor.

I never found a replacement for my Opmid but my Big Bore Kit worked fine for me up until I sold it.

FYI I also added a external oil cooler and that Kitaco Clutch cover with sythetic oil with cooler spark plugs, that in my mind also help a bit but with that Opmid sensor.. who really knew.. LoL"

So all was fine

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