2016 Yamaha YZ250F Moto-House MX - Refresh and Power-Up
The 2016 YZ250F is a great bike to start with and has given years of great performance. The dirt bike has a little over 90 hours on it and its time to freshen up and increase the power the keep up with the latest models.
This blog will be broken up in to three separate ones to keep the reading light !!
Let’s start talking about the crank shaft, replacing the crank at 90 hr. is done to prevent problems. You can always go longer, but when it fails the damage can be much greater and costly. The Yamaha timing chain does not last forever either, usually 20-25 hours so it should be replaced every time you freshen up the top-end (piston & rings). Another advantage to a rebuild is you will typically gain back 10% to -12% of power that was lost over time. So remember before you add performance parts you need a strong base. What I mean by that is if your motor need to be strong you can do other modifications. You will never see the horse power gains with a weak motor or the reliability.
If you are on a budget, I feel you are better off rebuilding a motor over adding performance parts.
The best way to rebuild is to purchase a Rebuild kit from either Wrench Rabbit kit or Wiseco Garage Buddy kit. Either kit is great comes wit everything you need.
The Wrench Rabbit kit includes, Hot Rods Crankshaft, Vertex piston kit, complete engine gasket kit, complete oil seal kit, main bearing and seal kit, water pump rebuild kit, transmission bearing kit, countershaft bushing/seal kit, cam chain and counter balancer bearing Kit.
The Garage Buddy Rebuild Kit - includes Wiseco standard series 4-stroke piston (stock compression ratio), complete gasket and any needed O-rings, water pump rebuild kit, Wiseco cam chain, all rotating and reciprocating rebuild kit - includes all top and bottom end components for a complete engine rebuild!
Both kit offer all you need to rebuild your motor, but the Wrench Rabbit kit also supplies you with transmission bearing kit and The Garage Buddy kit does not.
Now we Have to pick out a kit - we will use the Wrench Rabbit kit for this build.
The kit does not include any Valves and we will perform a 5 angle valve job and also port the head. Between the valve job and porting we will see significant power gains and still maintain reliability. Now we have to choose replacement valves to replace the worn out ones. The two options are Titanium OEM Replacement valves or Steel Conversion.
The first option we use the Hot Cams Titanium replacement valves (Exhaust Valves 8400036-1) and (Intake Valves 8400036-2) . The valves are sold each and are just valves so you will need valve springs and keepers I usually go with new OEM parts.
The other choice is Ti-Steel replacement from Pro-X. They are sold as a kit with both valves (2) and valve (2) springs. The reason is because the steel valves are heaver you need stronger valve springs. The stock OEM spring will not hold up. You will still need new keepers the OEM will work fine.
Steel valves offer increase durability at a lower cost over the OEM Titanium valves. The only downside is the weight which will very slightly heavier and can reduce power very slightly. Most cases riders can't tell the difference between Titanium or steel.
Next Post will be in a few days and we will Talk about the cylinder Head Work - See you Shortly