2003 yz250f new crankshaft, yes or no

[Natedawgrebuilds]

So im doing my rebuild on my bike and i took off the timing chain and the gear on the crankshaft for the chain is worn abit. Its not bad. I seen worse just some teeth are skinnier then other. Will try to get into the garage and take a picture for you guys but everything els on the crankshaft is fine there is no up or down play on the con rod, abit of side to side which is good. There also no play what so ever when moving trying to move the flywheel. So question is should i just leave the crankshaft in and ride it for another season or put a new one in?

 

[Natedawgrebuilds]

Here is some pictures. Its not bad but if u guys think i should replace i will. I rather pay the 280$ wiseco crankshaft, than the timing chain to broke and do some damage in the engine while i ride. I dont race. I ride in the pits around a small track and do freestyle so i do put some stress on the engine.

 

[Rich Rohrich]

Replace the crank. The damage that comes from the cam chain jumping a tooth is significant and expensive. With a crank gear this worn it is a real possibility.

This is a common wear point on the early YZ250F cranks.

 

[Natedawgrebuilds]

Replace the crank. The damage that comes from the cam chain jumping a tooth is significant and expensive. With a crank gear this worn it is a real possibility.

This is a common wear point on the early YZ250F cranks.

Yeah that what im gonna do rich. Gonna start splitting the case. I know im gonna need a crankshaft puller because i dont like the crankshaft in the freezer trick. I rather do it right so ill order that one tool but is there way to avoid the case splitter tool and clutch puller? What should i watch for when i split the crank. And i was told only the side where the timing gear is pressed one and the other side is a slip on. Is that true?

 

[Rich Rohrich]

Make sure and check the water pump seal and bearing while you have it apart. You don't need a case splitter for these engines, but you will need the tool to hold the inner clutch hub so you can break the center nut loose. Make sure you use a high quality 1/4 " torque wrench when you put the cam caps back together. Getting that part wrong can be expensive.

 

[Natedawgrebuilds]

Make sure and check the water pump seal and bearing while you have it apart. You don't need a case splitter for these engines, but you will need the tool to hold the inner clutch hob so you can break the center nut loose. Make sure you use a high quality 1/4 " torque wrench when you put the cam caps back together. Getting that part wrong can be expensive.

would a 3/8 torque wrench work for doing all the bolts that need to be torque or does it have to be a 1/4. and should it be in ft pound or inch pound

 

[Rich Rohrich]

You'll need a proper inch/lb torque wrench to reassemble the cam caps properly. A ft/lb torque will work for the rest of the engine. I usually use the Precision Instruments brand torque wrenches, but I also have a 1/4 Proto inch/lb wrench that has proven to be very reliable over the years. https://www.amazon.com/Stanley-J6060A-Ratcheting-Micrometer-10-50-Inch/dp/B002FCQGWM

Snap-On and the major tool brands all have good models as well.

 

[Natedawgrebuilds]

You'll need a proper inch/lb torque wrench to reassemble the cam caps properly. A ft/lb torque will work for the rest of the engine. I usually use the Precision Instruments brand torque wrenches, but I also have a 1/4 Proto inch/lb wrench that has proven to be very reliable over the years. https://www.amazon.com/Stanley-J6060A-Ratcheting-Micrometer-10-50-Inch/dp/B002FCQGWM

Snap-On and the major tool brands all have good models as well.

Just wanna be clear. So cam cap is the camshafts holder correct? When do you recomend changing the valve. Im thinking i ahouls get a vavle kit since the engine is already apart. One less problem i have to worry about after rebuild ahha

 

[Natedawgrebuilds]

Do you recomend putting blue loctight on every bolt i put back into the engine

 

[Rich Rohrich]

Yes the cam caps I'm referring to hold the cams in place in the cylinder heads. They also provide the bearing surface that the cams run on, which is why getting them torqued correctly is so critical. I've seen lots of Yamaha cylinder heads ruined because people didn't get this right. It's not difficult, it just takes some care. Given the age of the engine it's fairly likely that it will need new valves, new springs, valve seals and the valve seats resurfaced. If you end up going this route do yourself a favor and just spend the extra money and get a complete Kibblewhite racing spring kit and Black Diamond Stainless Steel valves.

http://shop.kpmivalvetrain.com/c/dirt_yamaha_wr-yz-250f-2001-2013

I've built hundreds of four-stroke MX cylinder heads using these Kibblewhite components and getting 300 hours out of the setup is fairly common. The OEM parts work very well, ,so if you are a budget you can use them as well as long as you have freshly machined valve seats. Just bear in mind if you ride a lot you'll be going through the process again much sooner with the OEM parts than with the Kibblewhite parts.

There is almost nowhere in the engine that you will be using Loctite. Most bolts that get torqued in the engine need to be clean and lubed prior to torquing. This is especially true for the bolts that hold the barrel and cylinder head to the cases. The OEM service manual does a pretty good job of describing what lube should be used for a specific fastener so try and follow their advice. If a bolt is designed to be torqued dry (no lube) the manual will usually call that out. Either way the bolt and threads need to be as clean as new. I use ARP Ultra Torque lube for most critical bolts when I'm building an engine.

http://arp-bolts.com/p/arpultratorque.php

There is lots of good technical info about how fasteners and torque work at the ARP link above.

 

[Natedawgrebuilds]

Yes the cam caps I'm referring to hold the cams in place in the cylinder heads. They also provide the bearing surface that the cams run on, which is why getting them torqued correctly is so critical. I've seen lots of Yamaha cylinder heads ruined because people didn't get this right. It's not difficult, it just takes some care. Given the age of the engine it's fairly likely that it will need new valves, new springs, valve seals and the valve seats resurfaced. If you end up going this route do yourself a favor and just spend the extra money and get a complete Kibblewhite racing spring kit and Black Diamond Stainless Steel valves.

http://shop.kpmivalvetrain.com/c/dirt_yamaha_wr-yz-250f-2001-2013

I've built hundreds of four-stroke MX cylinder heads using these Kibblewhite components and getting 300 hours out of the setup is fairly common. The OEM parts work very well, ,so if you are a budget you can use them as well as long as you have freshly machined valve seats. Just bear in mind if you ride a lot you'll be going through the process again much sooner with the OEM parts than with the Kibblewhite parts.

There is almost nowhere in the engine that you will be using Loctite. Most bolts that get torqued in the engine need to be clean and lubed prior to torquing. This is especially true for the bolts that hold the barrel and cylinder head to the cases. The OEM service manual does a pretty good job of describing what lube should be used for a specific fastener so try and follow their advice. If a bolt is designed to be torqued dry (no lube) the manual will usually call that out. Either way the bolt and threads need to be as clean as new. I use ARP Ultra Torque lube for most critical bolts when I'm building an engine.

http://arp-bolts.com/p/arpultratorque.php

There is lots of good technical info about how fasteners and torque work at the ARP link above.

Thats for the amazing advice rich. Gonna help my rebuild much easier as i know what to look for and too get and for goona go with that valve kit. Im already spending money on a new wiseco crank and i have a wiseco piston and ring in the package in the garage still, so redoing the valve is a damn good idea. Im already there ahah. Bringing this bike back to life with a nice new paint job. Exhaust and plastic. Will post picture when its all done and nice

 

[Natedawgrebuilds]

I hope my head is still good. The previous owner told me he just did a valve job and when i started my rebuild the bolts one the cam cap were loose, so i doubt he torque them:(

 

[Rich Rohrich]

Once you have the cam caps off and the cams out you'll be able to tell fairly quickly if the bearing surface of the cam or the caps has been damaged.