MXA BUILDS A BIG-BORE YAMAHA YZ270F: MORE OF A GOOD THING
Project bikes have a life of their own. Much like kudzu in Georgia, they start out small and grow uncontrollably. Take this bike, for example. The MXA wrecking crew wanted to build a 270cc version of our trusty, but used, 2014 Yamaha YZ250F. We felt that many Vet and play riders would appreciate the added horsepower and torque of a 3mm-bigger bore.
If we had stopped there, we would have been in and out of this project for around $650 in parts. In fact, that is exactly what Cylinder Works’ 269cc kit costs. It comes with a forged Vertex piston, Cometic gasket set and either a cast Cylinder Works cylinder or a bored-out stock cylinder that is replated by Millennium Tech. If you choose to bore out and replate your stock YZ250F cylinder, plan on a seven-day turnaround at Millennium.
The extra 20cc gave us 2 horsepower on the front of the powerband and 3 horsepower at peak—and it did exactly what we thought it would do; it chunked up the low-to-mid transition and damped down over-rev at high rpm. If you asked an MXA test rider what he thought, the most common answer would be that MXA’S YZ270F kit engine and stock YZ250F engine have nothing in common. They are completely different. If you are of Intermediate or up-speed, you won’t have much use for the Cylinder Works 269cc engine kit. It’s not as fluid as the stock YZ250F bore and stroke. It makes lots of power, but it doesn’t carry speed as well. The riders who loved the big-bore engine were Vets, Novices and play racers. The Vets liked the extra torque on the start, the Novices liked the power-now feel of an engine that didn’t require you to wring it out, and the play racers only cared about extra oomph to get over jumps.
IT DID EXACTLY WHAT WE THOUGHT IT WOULD DO; IT CHUNKED UP THE LOW-TO-MID TRANSITION AND DAMPED DOWN OVER-REV AT HIGH RPM.
And if it weren’t for the unending kudzu-like ebb of project bikes, this test would have been over. But, projects never come to an end. There is always something else to add to the package. We started this project to test the 269cc kit, and we came away with a solid horsepower gain and an accurate picture of who would like it and who wouldn’t. But, from that point on, everything we did was icing on the cake—and sometimes icing on the icing. Here is the kudzu list:
Fuel injection. Since we went big on the engine, we felt that we might be able to get more power and better throttle response with an Injectioneering throttle body and Vortex programmable ignition. We have always had good luck with Injectioneering’s unique butterfly design. The Vortex wasn’t as necessary, since the Yamaha’s ignition is easily programmable with the GYTR Power Tuner.
Airbox. We are not fans of Yamaha’s convoluted double-wall air intake system for the YZ250F and YZ450F. Cycra makes a very unique set of radiator shrouds that combine single-wall shrouds with air ducts to not only get more air into the airbox, but to make the YZ250F feel lighter and narrower. While we were in the airbox, we tossed the stock air filter for a $269 Twin Air PowerFlow kit.
Yellow plastic. You can buy stock YZ250Fs with blue or white plastic, which means that Cycra’s bright-yellow plastic package is the cool way to go. Cycra’s kit includes all the parts you need; all you have to do is add the graphics of your choice.
Exhaust system. Even though the 2014 Yamaha YZ250F has one of the best production exhaust pipes we’ve ever tested, it is possible to get a little more power from an aftermarket exhaust. Plus, a Ti system saves a couple pounds. Our pipe of choice was a FMF Factory 4.1 RCT Ti system.
Clutch. More power. More torque. More air. That means more pressure on the clutch. We didn’t go whole hog on the YZ250F clutch, but we did go to stiffer clutch springs, Hinson plates and, for looks, a Hinson clutch cover.
Brakes. Japanese motocross brakes are nothing to get dewy-eyed over in the pucker-power department. They are weak at best. The quick fix is to install an oversized 270mm front rotor kit. And while we were doing that, we discovered that we could get a complete set of Tusk wheels for under $500 to go with our Tusk brake rotors. So, we mounted our new rotors on red-anodized Tusk wheels (equipped with a Dunlop MX32 front and MX52 rear).
Suspension. As a rule of thumb, the MXA wrecking crew loves Yamaha’s SSS suspension settings, but the 2014 settings were stiffer than previous efforts and, for lighter, faster or slower riders, we felt that a valving change could fine-tune the suspension to suit each rider’s style. The stock setting works very well for a 170-pound Intermediate—lighter riders will need to go softer, and Pro-level riders will always go stiffer. We let Enzo Racing sort out the fork and shock internals. We went stiffer, but that’s just us.
Accouterments. No project bike would be complete without a full array of Renthal products—sprockets, chain, 997 TwinWalls and dualcompound grips. Works Connection added its Elite perch (with Y levers), brake caps, chain blocks and hour meter. Moto Seat did the black ribbed seat cover, and Raptor provided its amazing titanium footpegs.
It’s embarrassing to say, but our $650 YZ270F project bike set us back over $4000. But, you don’t have to be like us. We are weak. We are addicted to shiny parts. You can break this vicious cycle. You have the willpower to stop a project bike from attacking your bank account. Just say no to foof, anodizing and stuff you don’t need. We didn’t stop at $650, but we will pray for you.
MXA YZ270F PROJECT BIKE SUPPLIERS
Cylinder Works: www.cylinder-works.com or (515) 251-4070.
Millennium Tech: www.mt-llc.com or (888) 779-6885.
Vortex Ignition: www.vortexcdi.com.
Cycra Racing: www.cycraracing.com or (800) 770–2259.
Twin Air: www.twinairusa.com (800) 749-2890.
FMF Racing: www.fmfracing.com or (310) 631-4363.
Hinson Clutch: www.hinsonracing.com or (909) 946-2942.
Tusk: www.tuskoffroad.com or (800) 336-5437.
Renthal: www.renthal.com or (877) 736-8425.
Works Connection: www.worksconnection.com or (530) 642-9488.