Out of the arsenal of test bikes in the MotoUSA garage, Yamaha’s 2011 YZ250 has been in demand week in and week out. Although most of the major manufacturers have given up on the 2-stroke, we are happy to know that Yamaha hasn’t given up on that special place in our hearts for burning pre-mix. Check out our 2011 Yamaha YZ250 First Ride
review of the quarter-liter smoker to get the scoop on why we can’t get enough. While the bike is a blast to ride stock, we just can’t leave well enough alone. So we decided to see what could be coaxed out of the only camshaft-free Japanese 250cc motocrosser left on the market. We handed the YZ over to Pro Circuit to handle the engine duties, and Factory Connection was charged with tuning the suspension. We figured both of these companies would be just the ticket to turn the super-fun dinger into a super-fast ripper.
In the late ‘70s a one-time desert racing pro started a company based on his skill with 2-stroke cylinder porting and polishing in the Inland Empire of Southern California. That desert racer was Mitch Payton. Maybe you’ve heard of him and his juggernaut of the motocross
-racing world, Pro Circuit. If not, how did you get Internet access living under that rock? For over 30 years Payton’s expert tuners have been pumping out performance for amateur and pro racers alike.
The Pro Circuit cylinder and head modifications matched with the Works Pipe and R-304 silencer allowed our project YZ250 2-stroke to achieve power output close to a stock 2011 Yamaha YZ450F.
The goal for our YZ250 was to get the power and performance closer to the modern 450 4-strokes that have taken over the premier motocross and Supercross
racing classes. To up the power, Pro Circuit modified the cylinder and head to increase the mid-range and top-end power. Starting with the cylinder the master grinders opened up the ports. The port job consisted of raising and widening the exhaust port, cleaning up any inconsistencies in the transfer and boost port and then polishing all the ports.
Work on the cylinder head consisted of cutting the head and modifying the squish angle, length and size. The changes also altered the compression and combustion chamber size to work with the higher octane VP Fuel. These engine modifications are a black art, and Pro Circuit is one of the best at it.
Once the engine was reassembled a Pro Circuit Works Pipe
and R-304 silencer was added to complete the package. This was all the trickery that PC thought was needed to wake up the 2011 YZ250 and make it competitive with its 4-stoke rivals. For right around $700, Mitch and his boys were able to really turn up the juice on our project bike. That is why those in the know still think 2-strokes are a great alternative for the budget-minded racer and weekend warrior. After some break-in we rolled the Yamaha up on the dyno and the numbers were surprising. Peak horsepower with the PC tuned engine was very close to a stock 2011 Yamaha YZ450F
! Now that the power was sorted, we turned to controlling the super-light MXer.
Bike set-up is a personal endeavor, and what works for a 135-pound, 5’7” intermediate rider will not be suitable a pro that is 190 pounds and over 6-feet tall. Our test rider for this project, Scott Simon, knows this all too well. The ladies will say
The Factory Connection tuned suspension allowed the YZ to settle in the turns and handle chewed up sections of the track.
Scott is a tall drink of water; we just say he’s a beanpole. The stock suspension just wouldn’t work for his body type or skill level, so Factory Connection was charged with getting the chassis under control.
The crew over at Factory Connection
has tuned more than a few bikes for Scott, so they knew exactly where to begin. First order of business was swapping out the stock springs in the forks and shock for ones with heavier rates based on Scott’s pro-level speed and basketball player build. To counteract the amount of weight transfer from the front to back on the bike, the fork spring was increased from the stock 0.44kg rate to a 0.46kg rate. In the rear, the spring was upped 3 rates to a 5.6kg from a 5.0kg. The stock spring preload ring was replaced with a FC Team Works Pre-Load ring to reduce the binding effect on the spring during compression. A blue anodized top locking ring was the added to complete the factory look. To finish off the external mods Factory Connection added its FC Works HD Bump Rubber Kit for a more progressive feel with better bottoming control. The sag was set at 108mm. This would set the platform to tweak and fine tune the ride with modifications to the internals of the suspension.
Landings from big jumps was not a problem for the Factory Connection tuned YZ250 while still being plush on braking bumps and chop.
Starting up front, Factory Connection decreased the rate of the internal compression spring from the standard 2.0kg unit to a 1.7kg to allow the forks to settle deeper into the stroke with better compliance. The internals were reassembled with a set of Factory Connections 6mm lock nuts to ensure the proper torque setting on the valving assemblies. The fork oil level was set at 370cc. Turning to the rear, the suspension gurus paired a FC Compression Piston Plate with a Medium High Speed Compression Adjuster Spring for a plush ride on square edged bumps while improving high-speed bump performance.
To finish off the package for “Too Tall” Simon, a set of Tag Metals XT-1 Braced 1-1/8" Oversized Handlebars
was installed to open up the YZ’s cockpit area.
With just a few engine mods and suspension tuning the 2011 YZ250 can be competitive for the amateur racer.
When Scott rode the bike in stock trim, his biggest gripe was the suspension performance. Riding at the level he does, and as tall as he is, his expectations on suspension are always low but positive that preload and clicker setting can sort things out. However, on the YZ he struggled. An acceptable setting for one end of the spectrum would negatively affect the ride on the other end. It was either good at jumping or decent in the bumps, never both. Cornering was pretty good until the compression settings were increased to compensate for the bottoming issue. Once the YZ was stiffened up the bike would want to stand up in the corners and kick out on the braking and acceleration bumps. There just was nothing that could be done to allow Simon to ride the blue smoker to its potential.
After the Factory Connection tuning, Scott says the YZ is a whole different bike. He can charge into the jumps hard and not have to worry about over-jumping and landing flat. The reworked suspension handles big impacts without being harsh. On the flip side, small bump compliance is amazing. The bike is plush but can still handle the big impacts. Tracking has been greatly improved in the chop, and the bike will now rail through rutted corners. Gone is the problem with the bike standing up when slamming into corners. Scott says that the suspension is the biggest gain in performance on the YZ250 hands down.
When Pro Circuit was let loose on the engine Scott wanted more power, but not something that would rip his arms off. The idea was to make more power where needed to make it easier to ride, thereby making it faster. Mission accomplished. The midrange and top-end performance is
The 2011 Yamaha YZ250 Project Bike's Factory Connection suspension allows the rider to go faster through the chewed up sections of track that were problematic with the stock suspension.
greatly improved from stock. The project bike now rips out of the corners but is completely controllable. While the jetting was a bit off and boggy for Scott in stock form, after the PC motorwork the throttle response is now crisp and snappy. The use of VP Fuels
C12 fuel also helps get a little more snap.
Scott now thinks that the YZ250 is competitive with the newest crop of 4-stoke 450 machines. The bike is lighter and easier to throw around, allowing him to ride harder and longer. On all but the loamiest tracks the pumped up 2-stroke can now hold its own in the power department. If one was to make a career out of racing, of course, the better choice would be the 450, but the cost, ease of maintenance, and the light handling makes the YZ a superb choice for weekend or amateur racers. Plus nothing will ever smell as good as a 2-stroke on race gas.