My new project YZF450

41 replies to this topic
  • lumpy790

Posted November 20, 2010 - 06:43 AM


Picked up a 2008 YZ450F basket case off of craigslist in Charleston SC. :clap: The clutch basket had shattered and they already picked up a used clutch off of eBay and split the cases and cleaned it out. Closer inspection found cylinder needs to be replated :headshake and the ignition looks like a piece of metal got spinning and whacked one of the pickups cracking the coating. A little JB weld and we will see what happens. The head checks out good. Debating on getting a rod kit and putting it in since im already there......and I can press it in the crank my self.

Found a new OEM cylinder, piston, rings, pin, clips & gaskets on ebay for only $425.....and a complete aftermarket gasket set for $60 .......all should be delivered today. :bike:

Posted ImagePosted Image
Posted Image
Posted Image
Posted Image

Posted Image
Posted Image
Posted Image
Posted Image

  • lumpy790

Posted November 20, 2010 - 07:17 AM


When done its going to look like my YZ250 smoker.

Posted Image

  • Yamiryder

Posted November 20, 2010 - 07:30 AM


sounds like a fun build. good luck :p


Posted November 20, 2010 - 03:42 PM


That two stroke looks nice

  • mx730md

Posted November 20, 2010 - 03:47 PM


fun project.

what did you get it for if you dont mind sharing?

  • lumpy790

Posted December 04, 2010 - 08:52 PM


fun project.

what did you get it for if you dont mind sharing?

I paid a little more than I should have since I had to replace the cylinder.

Since the motor is basically all apart except for splitting the cases I decided to press a new rod into the crank.

  • motojase316

Posted December 05, 2010 - 02:48 AM


Keep the pics coming, looks interesting...

  • motojase316

Posted December 05, 2010 - 02:50 AM


Might need a rear sprocket on the list too lol... they got their moneys worth out of that one :thumbsup:

  • Erik Marquez

Posted December 05, 2010 - 08:01 AM


Fun project..
Interesting Odd man out bolt in the cam cap.
Posted Image

Find anything funny with the head? helicoil for the one bolt? Cams binding in bores after cam caps tq down?

  • lumpy790

Posted December 05, 2010 - 08:42 AM


I noticed the bolt and checked the head out closely before buying it. Threads were fine. Usually these bolts stretch and break before the threads get damaged. The cam cap bolts are already on my OEM parts list.

I will be swapping the Red wheels & rear sprocket off of my 2 stroke and already had a front cog.

My wife will be traveling for the next 2 weeks so my plans are to do a bunch of work on the Moto Hose Box Van and the YZF .........get to use the kitchen table...hehehehe

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • lumpy790

Posted February 06, 2011 - 09:21 AM


its been a while since I updated anything about this build.......when I bought it I was told "all you need to do is put it back together" but after closer inspection I found wear on the cylinder from the piston being in to long. When I water checked the valves there was no leaking so the head seems ok. I picked up a cylinder & top end. Since it was already pretty much apart I decided to press in a new rod and main bearings and cam chain. Thank you Chuck at Privateer Connection for pressing the new rod in for me!

I have been procrastinating pulling the valves out to pop new valve seals in but tore it apart last night. This is my 1st time dealing with TI valves (400 & 426 had steel valves) and I am not sure if these are OK or not. I cleaned them up a little with a Brillo pad.


Posted Image


Posted Image

What do you guys think? Are they good?

If not what brand of aftermarket valves do you recommend?

  • KJK_JR

Posted February 06, 2011 - 01:54 PM


I'm no expert with valves but it looks like they have a little bit of wear. I would replace them and have the seats recut. Go OEM

Edited by KJK_JR, February 06, 2011 - 02:32 PM.

  • grayracer513

Posted February 06, 2011 - 02:29 PM


They look like they are currently serviceable, but the trouble is that there isn't a way to tell with any accuracy how much of the hard coating is left, since it starts out so fantastically thin. The exhaust valve actually looks better than the intake. The fact that there is a uniformly "clean" wear pattern on the intake face indicates that there is "some" wear. The coating on the valves is only about .0006" thick so measuring the wear is nearly impossible.

And again, if you reuse them, which you could right now, there's no way to know when they'll wear through and start sinking.

I would replace them with OEM Yamaha valves as opposed to any aftermarket product unless you're building a very high output, serious race only engine. In that case, I'd ask Ron Hamp at Ron Hamp Cycles what he uses on his 60+hp YZF's.

  • lumpy790

Posted February 10, 2011 - 08:39 AM


I am obviously paranoid from the people who put down thumpers!

After bead blasting all of the valves there was no wear. It was all carbon!

Again..... a huge thanks to Chuck at for helping me out and giving an honest opinion! BTW.....if your at an East Coast SX this year you can say hi to Chuck as he is Jimmy Weinert Racings - #44 Les Smith's mechanic.

Motor is 99% ready........found the clutch nut was missing

  • grayracer513

Posted February 10, 2011 - 08:55 AM


After bead blasting all of the valves ...

:smirk: Please tell me you used plastic blasting media.

  • lumpy790

Posted February 10, 2011 - 09:36 AM


Chuck mentioned it was glass beads

  • grayracer513

Posted February 10, 2011 - 09:43 AM


There is a fairly good chance that using glass media on the valve faces may have been detrimental to the hard coating. Not a good idea.

  • lumpy790

Posted February 10, 2011 - 10:35 AM


Chuck is a professional motor builder here and I doubt he would have steered me to his cabinet if it was going to be a problem.....probably why he does not use the standard blast material sand.

  • KJ790

Posted February 10, 2011 - 04:23 PM


Chuck is a professional motor builder here and I doubt he would have steered me to his cabinet if it was going to be a problem.....probably why he does not use the standard blast material sand.

Does he deal with titanium valves much? Blasting them is fine for a steel valve, but I personally would never blast a titanium valve. Ti valves have a very thin ti-nitride coating that is what makes them tough. Once that coating is gone your valves will begin to tighten and will be toast in less than 10 hours. This is why people who don't maintain their air filters have problems, the dirt going into the engine damages the coating and their valves tighten up in a matter of hours. This is the same reason why you should never lap titanium valves either.

  • lumpy790

Posted February 10, 2011 - 07:25 PM


Chuck builds MX motors every day and has for many years........ Builds Ti valved heads just about every day.

Related Content


2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Wilson the Blue Privateer by jetfuel

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017

BIGBORE FOR YZ450F 2006? by Taattie94

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.