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Trail Bikes 186cc Big Bore Kit - Grom / MSX125 / Monkey (2014-2021)

Trail Bikes 186cc Grom / MSX125 / Monkey Big Bore kit
Pricing: $273.95


TB 186cc Big Bore Kit Grom / MSX125 / Monkey Fits: 2014-2021 Models (Does NOT fit 2022-UP as that model has a totally a new motor)

Piston size 64mm
Stroke (OEM crank) 57.9mm (For you that enjoy math that's a whopping 186cc of Grom stomping power) Get some Grom wheelies going!!

For you that know Trail Bikes is the USA leader in performance big bore kits for the Honda 50, 70, 100, and 110cc models.

This is the largest Grom bore kit available on the market and is as big as you can go without having to bore your cases.

Kit Includes:
- 64mm Aluminum Ceramic Plated Cylinder. (Lighter than steel or even steel sleeved aluminum cylinders on the market.
(Reduced friction, better ring to cylinder sealing, better heat transfer which means it runs cooler and cooler down quicker. ALL equating to more power!
- High quality 64mm piston kit that include rings, wrist pin and clips. The pistons are CNC machined to exacting tolerances.
- Complete 64mm top end gasket kit

These are high quality parts and definitely will dramatically increase the power and fun factor on your Grom!

Trail Bikes Oil cooler kit (Sold separately) is recommended. (BTW we do have a kit that offers the oil cooler to go along with this big bore to save you a few bucks!)

Please NOTE: Must be used with an aftermarket fuel controller to prevent a lean condition and damage to your engine

Check out our Fuel Controller Kit for Honda Grom / MSX 125 on (Grom / MSX125 page)

Ceramic coated all aluminum cylinder
Includes gasket kit
Large cooling fins for efficient heat dispersion
Ports on cylinder allow for an external oil cooler (Part No. TBW9153)

Grom - 2014-2021
Monkey - 2014-2021


  • K9150TB
  • K9150TB
  • Trail Bikes
  • New


Shipping Information

  • Item Requires Shipping
  • 5.0 lbs.
  • W10.0000” x H7.0000” x L8.0000”

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