Is A 144cc Big Bore Kit Worth It On A 125?

Are you looking for that small further energy to get around a certain leap? Or is it due to the fact you want to confirm to your four-stroke pals that two-stroke grime bikes nevertheless have what it usually takes? Either way, a significant bore kit can help you do that.

YZ125’s are the most typical 125’s in U.S., and for a excellent purpose. Yamaha is the only Japanese manufacturer that imports two-strokes to The usa. They are fast, gentle, trustworthy, and entertaining. But, for some of us that just want a small much more out of a tiny-bore two-stroke, an up grade in displacement is probably on leading of the listing of modifications.

Just Mainly because It really is 144cc, Will not Indicate It’s A 144…

You can get a bored out cylinder that is 144cc’s, but to truly accomplish like a 144 it will want some correct tuning. This is why you will hear beneficial and unfavorable opinions from people today who modify their 125 to a 144. Most of the time, it really is the individuals who get just a cylinder package that give terrible responses. This is due to the fact the cylinder, carburetor, and exhaust are not thoroughly tuned for the excess cc’s. When I say a cylinder package, I am conversing about just one you can buy from a enterprise like Athena and just bolt it on.

You Are unable to Go Faster With no Extra Fuel

Far too many folks feel they can make their dirt bike more rapidly by bolting on elements and not do everything else. Motocross bikes are substantial-tech racing equipment, so it can be critical that they are finely tuned. If you will not tune a bicycle after putting on a “hop-up” component, it really is almost certainly likely to operate worse, and probably crack shortly down the road. Extra ability involves a lot more fuel, so if the carb just isn’t feeding ample fuel to the cylinder, it’s not going to run like it should really. If your bike was effectively jetted just before you modified it, then it will run lean soon after. You will have to go up on the primary jet at the minimum. A change in pilot jet and clip place on the needle may perhaps also be expected for the best possible functionality.

Even larger Motor Wants Bigger Pipe

Get a glance at the sizing and shape differences from a 125 to 250 two-stroke pipe if you have not before. Bigger engines have to have even larger pipes to consider advantage of the higher displacement. Sure, that suggests if you might be working with a inventory pipe on a 144, then you most likely usually are not earning the most out of the engine. Some providers make specific pipes for significant-bores, but may possibly value a very little far more (nonetheless much less expensive than four-stroke exhaust by a long shot). If you want to stick with FMF or Professional Circuit, do some investigation on which pipe performs nicely for your dirt bicycle, for the reason that not each individual pipe and bike combination will give you the identical result.

Build The Best 250F Killer

Now if you get your 125 two-stroke bored and designed by a respected bicycle builder, it can be out of this globe. In addition to uninteresting and plating the cylinder, most builders will port the intake and exhaust ports to your liking (either very low to mid-selection or mid to major-end electricity for most builders), modify the port timing, possibly do some scenario mods if you mail your full engine in, and cylinder head mods if you want greater compression (will need race gasoline). In end result, this will make a screaming-fast compact-bore two-stroke that will outrun 250F’s and maintain up with 450’s with an seasoned rider. Oh yeah, did I mention most stores can do this for rather low-priced too!? That’s proper, who desires a higher-buck four-stroke when you can consume them up with a finely-tuned 125/144…

Athena Failed to Know What They Had been Executing…

Whilst I acknowledge that I have by no means owned a 125 with an Athena 144cc kit, I have completed plenty of investigation to locate up what is actually up. In fact, I failed to have to go quite far to discover out if it truly is worthy of it or not. Review just after assessment confirmed that the Athena best-conclusion package did not increase the inventory YZ125 by a lot. They in essence took the inventory cylinder, enhanced the electric power-valve size and ports, and known as it fantastic…… You can see a slight boost on the dyno, but to truly come to feel the result of the extra cubic-centimeters you have to port it like you would a stock cylinder. The port measurements, styles, and durations will not be the exact as a 125cc if tuned effectively. This is when the trustworthy two-stroke engine builder arrives in. There are builders that actually know how to open up a 144 up to its likely, so do not settle for a lot less.

This is a terrific instance of a YZ144 Athena Kit Examination done by Motocross Action Journal. They do an in-depth critique of it, and in the end their YZ hardly makes an excess two ponies, and which is with a GYTR pipe and silencer created for the 144!! If it is effectively tuned, I honestly assume you need to be in a position to crank out 5-7hp additional than a inventory 125.

-Tom Stark