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blurz28

06 YZ450 top end questions

19 posts in this topic

Going to be rebuilding the top end this winter. I plan on replacing the piston/rings, valves, and cam chain.... I plan on using all OEM parts.

Is there any need to replace the con rod?

Any thing special I need to look out for?

Also, I haven't had any trouble with the bottom end but I want to do everything all at once.

So anything there I need to check that I can do without splitting the cases?

Thanks

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Always check the rod for excessive side to side play. If the rod has any vertical play at all it's trash. But chances are, if it was just running and no odd noises were present then the lower end should be fine. How many hours roughly are on the crank? And why new valves? If those are the titanium valves those are gonna be pretty pricey and not necessary unless worn past their limits. Personally I would replace top end, timing chain, and do a valve adjust and you should be ready to rip.

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I have no idea, and that's the problem..... I traded my 05 yz250 for it and have no idea how much time is on it. Valves are roughly $60 each on boats.net and I'd rather replace everything so I can start from zero. And from what I've read once the valves need adjustment it's just a small amount of time until they need replaced and I'd rather just tear it down once.

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I have no idea, and that's the problem..... I traded my 05 yz250 for it and have no idea how much time is on it. Valves are roughly $60 each on boats.net and I'd rather replace everything so I can start from zero. And from what I've read once the valves need adjustment it's just a small amount of time until they need replaced and I'd rather just tear it down once.

thats not true, valves can last practically forever, you only need to replace valves if your valves are in spec and still dont seal properly. Just shim them until you run out of shims small enough to get your clearance into spec. Replacing valves for no reason wont benefit you also because your valve seats go just as soon as your valves do.

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From what I've read here, and maybe gray will chime in here, yz valves will tolerate 1 adjustment and after that you're on borrowed time.....

I'd much rather replace them than worry about grenading my motor....

Seems like a small price to pay for peace of mind. I'd rather spend $300 to replace valves than who knows how much if I drop a valve

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From what I've read here, ...yz valves will tolerate 1 adjustment and after that you're on borrowed time.....

 

 

That is a fact.  Once you have dropped to the second size smaller shim, it's only a matter of time.  The hard coating on the valves is less than .001" thick, and once it wears through (which takes an incredibly long time on a YZF) the valves wear very quickly.  Because they won't necessarily wear in an evenly concentric pattern, they can start "scrubbing" laterally as they close, which stresses the stems unnaturally, and can lead to the whole valve head dropping off.

 

The thing to do is remove them and have a look.  ANY detectable wear into the surface of the valve face is grounds for replacement.

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I raced the snot out of my 07 and 09 and never even needed an adjustment. However I do agree with replacing if worn I have seen Yamaha valves (as well as other valves) that become beveled at the valve seat and I think that is what Gray is referring to. Once wear starts it occurs rapidly. Again replace anything worn and in my opinion nothing that is not. Save that money for when something is truly worn. You can play the ticking time bomb game with every moving part in your motor and on your chassis (even new parts) and drive yourself insane. Every part has limits, tolerances, and strengths, and some even defects, that is the scary financial reality of our sport :))))))

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My motivation to replace valves, top end, and cam chain are really just to be able to truly know how much time will be on them.

If I had the funds I'd yank the motor and replace every bearing, seal, and worn part just so I could say I have a nearly new 0 hour motor.

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A very commonly overlooked part is the valve spring too. You don't want to cause any valve float on your nice new valves and piston. You might also want to get the seats recut in your head since your getting new valves too. I think its like $85 at MX Time

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I've been researching where to send it out to have the valve seats cut...

I'm in Tulsa, OK. It's not huge but not small either so I'm sure there are some places around that perform the service.

I guess I need to call around and see what I can find out.

I'm not opposed to sending it out if I have to

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You might also want to get the seats recut in your head since your getting new valves too.

 

That's an interesting statement.  In fact, if you don't have the seats refinished when you replace the valves, what you might do instead is just throw $400 worth of new valves in the trash.  It will save time.

 

The local dealerships in your area have to have someone to go to to get this done.  Ask them who they use.

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Be sure the shop has experience with the YZF.  It is imperative that as little material as possible be removed from the actual seat in order to keep the valve stems a serviceable distance from the camshafts.  If too much seat is cut away, there will be no shims small enough to correct the valve clearance, and the stems cannot be ground shorter to compensate.

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I'm sure he does. I asked for a price for a 3 angle job for 5 valves and he instantly asked if it was for a yz 250 or 450.....

Can the seats be replaced or do you just have to buy a new head?

Edited by blurz28

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Yes, seats can be replaced if they get too beat up to use.  Guides, too, but valve guide wear on YZ450's takes a very long time to get to the point of needing service, owing mostly to the design of the valve train. 

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Might as well get some input on a clutch basket instead of starting a new thread.....

I've looked at them all (I think) and they all kinda look the same to me....

Hinson and moose look the same wiseco and gytr look very similar I think rekluse requires the use of their inner clutch hub

Barnett is out for me because I don't like the look of the inserts or the rivets or whatever is holding them there

So, is one better than another as far as durability goes?

Cause their prices have a pretty wide range.

Is the hinson steel better than the billet?

Thanks

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GYT-R is Hinson.  Either is the best in the business, IMO.  I frankly don't see a reason for the steel basket.

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That's good to know. Consequently, the gytr is the cheapest of the bunch by about $50 so that's what I'm gonna go with

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