How big can you bore a YZ125?

How big can you bore a YZ125?

The 1999 – 2018 Yamaha YZ125 134cc / 144cc kits are our most popular M-Spec Big Bore Kits! We strip your stock cylinder, weld the ports for perfect port timing, then bore the cylinder from 57.5mm to 56mm (134cc) or 58mm (144cc). The cylinder is then hand ported for your riding style.

Is a 144 big bore kit worth it?

Going from a 125 to 144 can be a game changer even if you’re just trail riding. The 144cc kit alone will boost the bottom-end to mid-range power, and that is exactly where a 125 2-stroke needs help for off-road riding.

Does a big bore kit add horsepower?

The most effective big-bore engine is the 250 four-stroke. By going to a bigger piston, enough to get it up to 270cc that can add as much as three horsepower.

What does a big bore kit do for a dirt bike?

A big bore kit typically consists of a new larger bore cylinder, piston kit, and top end gaskets. They replace your stock Original Equipment Manufacturer (OEM) parts and increase horsepower and torque by increasing the engine size (displacement).

How much HP does a YZ 125 make?

33.53 hp
The engine produces 35 hp (26 kW). The YZ125 has been built with five- or six-speed manual sequential gearbox depending on model year….Yamaha YZ125.

Manufacturer Yamaha
Engine 124 cc (7.6 cu in) reed valve two-stroke single
Power 33.53 hp (25.00 kW)
Transmission 5- or 6-speed sequential manual
Suspension Mono-shock, 13 inches travel

How much is a YZ 125 worth?


Suggested List Price Average Retail
Base Price $6,499 $5,970
Options (Add)
Total Price $6,499 $5,970

Does a big bore kit increase compression?

Second, a large overbore such as the 3mm over kits that are popular right now actually results in increased cylinder compression, more than stock in other words, due to the sizeable jump in cylinder volume versus the unchanged combustion chamber volume.

How heavy is a YZ125?

190 lb
Yamaha YZ125

Manufacturer Yamaha
Seat height 100cm1,000 mm (39.3 in)
Weight 86 kg (190 lb) (dry) 94 kg (208 lb) (wet)
Fuel capacity 7.9 l; 1.7 imp gal (2.1 US gal)
Related Yamaha YZ250F

How many 144cc big bore pistons can I put on my YZ125?

Now that it’s done, you can install as many 144cc big bore pistons as you want on your YZ125. A stock piston will work as well if you desire to go back to 125cc.

How do I Make my YZ125 into a yz144?

The easiest route to making your YZ125 a YZ144 would be to install the Athena big bore kit. It has everything you need, from piston and cylinder, to all the gaskets. It’s no more difficult to install than replacing the piston in your 2-stroke. Click here or the picture below to order your YZ125 Athena big bore kit from Amazon today.

Will A 58mm piston skirt fit on a YZ125?

Yes, unfortunately there’s some minor crankcase mods that needed to be done to make this piston fit. Obviously, having a bigger piston requires more room. The bottom of the Athena 58mm piston skirt will just barely hit the YZ125 crankcase if not relieved.

Which YZ 125 pipe should I buy?

A stock YZ125 pipe is still a good choice if you want to save money. It’s also good to keep low-end and mid-range power, which is great for trail riding. A stock YZ 125 pipe won’t put out high peak horsepower numbers with a 144 kit, but you’ll have a lot of usable power.