Are you hunting for that minor added electricity to get above a selected jump? Or is it mainly because you want to establish to your 4-stroke mates that two-stroke dirt bikes nonetheless have what it requires? Both way, a major bore package can help you do that.

YZ125’s are the most popular 125’s in U.S., and for a very good reason. Yamaha is the only Japanese manufacturer that imports two-strokes to America. They are rapid, mild, reputable, and enjoyment. But, for some of us that just want a small a lot more out of a tiny-bore two-stroke, an enhance in displacement is probably on major of the listing of modifications.

Just Simply because It’s 144cc, Will not Mean It is really A 144…

You can get a bored out cylinder which is 144cc’s, but to truly complete like a 144 it will want some proper tuning. This is why you will listen to constructive and unfavorable reviews from men and women who modify their 125 to a 144. Most of the time, it truly is the people who invest in just a cylinder package that give bad feed-back. This is simply because the cylinder, carburetor, and exhaust are not properly tuned for the extra cc’s. When I say a cylinder kit, I’m chatting about one you can get from a organization like Athena and just bolt it on.

You Are unable to Go A lot quicker With out A lot more Gasoline

Much too several men and women assume they can make their filth bicycle faster by bolting on pieces and not do nearly anything else. Motocross bikes are superior-tech racing devices, so it is significant that they are finely tuned. If you never tune a bike right after placing on a “hop-up” aspect, it is really probably heading to operate worse, and potentially break shortly down the road. Extra energy necessitates a lot more gas, so if the carb is not feeding adequate fuel to the cylinder, it can be not going to run like it ought to. If your bike was appropriately jetted before you modified it, then it will operate lean just after. You will have to go up on the key jet at the minimum amount. A alter in pilot jet and clip position on the needle may perhaps also be essential for optimum overall performance.

More substantial Engine Demands Larger Pipe

Acquire a seem at the dimensions and condition differences from a 125 to 250 two-stroke pipe if you haven’t before. Even larger engines require bigger pipes to take gain of the greater displacement. Sure, that means if you are using a stock pipe on a 144, then you almost certainly are not generating the most out of the motor. Some businesses make special pipes for massive-bores, but might price tag a very little more (however much less expensive than four-stroke exhaust by a extensive shot). If you want to adhere with FMF or Professional Circuit, do some investigate on which pipe will work effectively for your grime bicycle, simply because not each pipe and bike combination will give you the same result.

Develop The Ultimate 250F Killer

Now if you get your 125 two-stroke bored and constructed by a reliable bike builder, it can be out of this globe. In addition to unexciting and plating the cylinder, most builders will port the consumption and exhaust ports to your liking (possibly lower to mid-assortment or mid to major-conclusion ability for most builders), change the port timing, maybe do some scenario mods if you send out your whole engine in, and cylinder head mods if you want higher compression (will demand race fuel). In result, this will make a screaming-rapidly small-bore two-stroke that will outrun 250F’s and keep up with 450’s with an expert rider. Oh yeah, did I point out most retailers can do this for rather low-priced too!? Which is right, who wants a high-buck four-stroke when you can take in them up with a finely-tuned 125/144…

Athena Failed to Know What They Have been Doing…

Even though I confess that I have by no means owned a 125 with an Athena 144cc kit, I have accomplished a lot of analysis to find up what is up. In truth, I did not have to go really much to come across out if it’s worth it or not. Critique right after assessment confirmed that the Athena top rated-stop package did not enhance the stock YZ125 by a great deal. They mainly took the stock cylinder, enhanced the energy-valve dimensions and ports, and named it good…… You can see a slight boost on the dyno, but to truly really feel the influence of the added cubic-centimeters you have to port it like you would a stock cylinder. The port dimensions, designs, and durations will not be the exact as a 125cc if tuned appropriately. This is when the reliable two-stroke motor builder will come in. There are builders that actually know how to open up a 144 up to its possible, so you should not settle for fewer.

This is a terrific example of a YZ144 Athena Package Take a look at accomplished by Motocross Motion Journal. They do an in-depth evaluation of it, and in the close their YZ scarcely will make an added two ponies, and which is with a GYTR pipe and silencer made for the 144!! If it really is effectively tuned, I actually think you need to be equipped to crank out 5-7hp more than a stock 125.

-Tom Stark

Resource by Tom Stark