How often will you re-build a 450?

I was reading the rmz forum and they said that the yz valves can only be re seated or something like that only once? That make any sence? IDK what that means if anything

BUt how often will I have to rebuild a yz if I get it? I am going to get a 450 just having troubles between green or blue.

Do they have to get rebuild often? I am not an mx racer i do ride woods and am going to do hares.

thanks

also what will it cost?

Get the YZ 450f! If you ride in the woods expect to adjust the valves once a year and rebuild the topend every 4-6 years. Maintence is key, you cannot ride it hard and put it away wet like your DR-Z 250. Clean the airfilter every ride and change the oil every three rides to keep the big thumper healthy. My cuz has a friend whos dad has a 02 YZ 426f and he uses that same maintenance schedule and the bike is still on the original top ends and starts on the first or second kick every time :applause:

Awesome Thanks For The Info!

Hmm...

My last yz went 240hrs and never needed a valve adjustment (it was a 250f but still, same basic 5valve head design afaik). I think a new top end is a good idea more often than 5 - 6 years, especially if you're racing.

Get the YZ 450f! If you ride in the woods expect to adjust the valves once a year and rebuild the topend every 4-6 years.
Once a year? I've checked mine 4 times, and so far, it hasn't needed an adjustment yet. My first response to the question of how often you have to rebuild a YZ450 is to wonder whether anyone other than hardcore racers have ever rebuilt one.

This is why I bought a Yamaha, I can do the regular oil change filter clean thing no problem but really don't want to get into new head stuff.. :applause: with my butterfingers that would mean only one thing.. Off to the motorcycle repair shop. So far no problems but I only have about 30 hours up... I do the maintenance and it runs good as new.. I guess it is almost new...

OK so I am definilty contemplating the yz. Is it real hard to start? I ride a two stroke and I sat on this bike this weekend and it is really tall for me. I am 5'5"

The height should be no problem for me other than starting it on flat or rutted ground. What if i kill it on the trail?

So are they hard to kick over?

Will the suspension sag a bit after use? yamaha says that it is like a 38.8 seat height right?

Thanks

I put a piston in my 426 last winter. As soon as I tore it down I could see that it was a waste of time, everything looked brand new. I did have to adjust all 3 intake valves recently, and I have plans on replacing them this winter. It probably doesn't need the new valves, but you never know. If Yamaha had a weak link, I would say it is the timing chain, it needs replaced every year. Its cheap and easy to do, and if you don't replace it you may have to buy a crank some day. I will probably never stray away from blue bikes, I have never owned a bike so versatile and bullet proof. In the famous words of Grayracer "I've had more problems out of my sundial than my YZF"

In the famous words of Grayracer "I've had more problems out of my sundial than my YZF"

Or "there are more cars out there in the streets that are less reliable than my YZF" :applause:

Aw, you guys remembered. :applause:

As far as starting, it's different from a two-stroke. But all you need to do is learn the rules and you should have no trouble. I'm, um, older, and only about 5' 10", and I don't have any real trouble with mine now that I know how it likes things done.

How often will you change the valve springs?

How often will you change the valve springs?

I'm going to change mine with the valves (first time). They say to change them a little more often, but I don't get that close to the rev-limiter. The higher revving 250F's go thru springs a lot quicker.

Hmm...

My last yz went 240hrs and never needed a valve adjustment (it was a 250f but still, same basic 5valve head design afaik). I think a new top end is a good idea more often than 5 - 6 years, especially if you're racing.

My trusty old YZ400F had it's valves checked (for first time, my bad!) last winter, and they're still within tolerance. Good old steel valves, more reliable/maintenance-free I've heard than the titanium ones. But it has relatively little time on it for a 6 year old bike.

I'd say for a regular racer a top-end rebuild would be every 3 years. Of course valve clearances checked more often!

I think the specs most of these guys are giving you are if you were to buy a brand new YZF. If you were to buy an older second hand one you definitely wouldn't get 4-6 years before rebuilding it! Unless it had just recently had a rebuild before your purchasing of it.

I posted on this thread two years ago. Still riding the same YZ no rebuild for top end in sight..

WOW, just realized how old the thread is! Who dug this up lol

You did. And the '03 YZ450 I first posted about in this thread in '05 was the one I just sold January '08. It was NEVER rebuilt and NEVER needed a valve adjustment and was a second hand bike when I bought it in '04.

My friend had his 07 engine blow up due to a valve spring lat year. He races reaaly hard and even with the last race lost he was 3rd overall in the season...

It was the end of the season and he swears he checked the valve clearances before every other race... Is there a way to check the springs without removing the head etc?

My friend had his 07 engine blow up due to a valve spring lat year. He races reaaly hard and even with the last race lost he was 3rd overall in the season...

It was the end of the season and he swears he checked the valve clearances before every other race... Is there a way to check the springs without removing the head etc?

Sometimes when you fool with something too much you introduce problems. Checking the clearances every other race is for 05 and earlier Hondas and Kawasaki's.

get you kicking leg ready if you're coming off a 2 stroke to a big 4. you can hand start a 2 stroke 125... big four stroke requires some big kicking. also remember you might not hit a compression stroke every kick like on a 2 stroke. can be frustrating, but the endless torque and fewer gear changes are worth it.

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