Ok, so it's that time of year again. Racing season is just around the corner and we are building a race bike for Trevor. This bike will be raced in the NCHSA series in the Pro class. Trevor purchased the bike around June of 2011. It's a bone stock 2010 Yamaha YZ450F and the story is it was Thad Duvall's practice bike. Trevor really liked the bike and decided this would be his race bike for the 2012 season. From here the bike will be completely torn down and put back together piece by piece to insure everything is ready for racing. Yamaha built this bike with Motocross and Supercross in mind. That being said it's still a decent woods bike in stock form but the power characteristics could be much better for the woods and that's what we intend to do. Trevor likes tractor like bottom end but he still wants good power everywhere else along with plenty of overrev and that's what we plan to give him. I'll be posting the information as we go.



So this is what we have to work with. It's a good clean bike that is in good overall condition. In the end it will get a full engine rebuild, and new plastics and graphics, along with some modifications to make it better suited for the woods.
Getting into the engine we've found that it's all stock and most likely never had a rebuild. The cases will get a good cleaning to make them look better than new. The cylinder has a small nick in the plating and will be sent off for replating. Since we don't know how much time is on the engine the crank will be rebuilt and while the cases are apart the transmission will get some attention too.
The cylinder head is in good shape. All of the valves are perfect aside from some carbon build up. The head will be disassembled, cleaned, and resurfaced. We will replace the valve springs and the head will get some port work to increase bottom end power.
The head has been cleaned, ported, and reassembled. The combustion chamber is reshaped to provide better airflow and atomization of the fuel. This was the first 4 valve Yamaha head I have ported and it is quite a bit different than any of the other heads I have done. The goal was to increase the bottom end torque but still maintain the mid range and top end snap this bike has. For the tight woods courses power in the lower RPM range is very important.
We got the cylinder back from Millennium Technologies. They do excellent work! The plating is better than stock and the clearance with the piston is dead on. Having the correct piston to cylinder is very important to get the most power out of the engine. To learn more about Millennium Technologies visit their website at: Millennium Technologies
The crank has been rebuilt and the transmission has gone through the ISF process. This make an incredible difference in how smooth the transmission shifts plus it reduces friction and frees up horsepower. This is something any race bike should have done. Now it;s time to get the bottom end back together and ready to go back in the frame.
Before we put the bottom end back together the cases get a thorough cleaning. They get a workover with Scotchbrite to remove all the stains. This is time consuming and a lot of work and even though it doesn't increase performance it definitely looks good. In this photo one of the case halves has been done while the other hasn't. In the end it is well worth the work.
For this bike we're using a CP piston. This is a 13.75:1 compression ratio and is what CP calls their full race piston. The increase in compression will add power everywhere but should also bump up the bottom end. It also comes with a DLC coated wrist pin for increased life. For more information go to: CP Pistons
With the engine cleaned and assembled it is now back in the frame. Speaking of the frame, while it was bare it was cleaned too along with a little polishing to give it a one of a kind look. All of the wiring was removed, cleaned and inspected for damage. With the fuel injection there are a lot more wires than a carbed bike and we want to make absolutely positive everything is like it should be. All of the bearings were also inspected. The steering stem and shock bearings were replaced and everything else was thoroughly cleaned and greased. Now it's on to assembling the rest of the bike.
Mark Hilton of Motovations Racing took care of the suspension on the bike. In the woods the suspension is extremely important and Mark is the best. Trevor was very happy with the Motovations suspension set up on his 2009 YZ450F last year and I'm sure this year will be no different. Check them out at: Motovations Racing
Ok, so here is the "nearly" completed bike. We've put the old plastics back on for now while the testing is done. We already have new plastics and graphics on the way and we will get them on just before the first race. I'll get the completed photos up soon.
Ok, so here is the finished bike. Unfortunately the fuel pump failed on the face of a jump during testing. Let's just say that's not a good thing. Completely trashed a set of bars and the silencer and did a little damage to the rider too. We replaced the fuel pump and added a new Leo Vince slip on to the bike. We also added the new plastics, graphics, and the seat cover. So far Trevor really loves this bike. The power is perfect and it handles great. At this point he has put 9 hours on the bike and other than the fuel pump failure it has performed perfectly. Thanks to everyone that helped us out on this project. We couldn't have done it without you!


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