Valves on my '08...

[Wiz636]

Just installed a new timing chain (3rd one actually) as insurance and of course checked the valves while I was in there.

At 171.4 meter hours the valves are still perfectly in spec. I love these motors

[grayracer513]

Gee, that's awful.

I don't know how to respond to that.

You must be disappointed.

[Family Man]

I know these motors are great. Very nice. High performance and high mileage.

[brentn]

Wow, I really hope that I can say the same thing!!!

Going to check mine here at 10 hours, maybe save it for 20, don't know yet. But if they're out of spec you gotta wonder what the hell I'd be doing wrong. I change the oil every 2 hours on this thing, filter every other.

[rcdude33]

That's crazy! I'm gona get a four stroke soon I got a yz250 and I may look into a 250f or a 450f yamaha of course!

[grayracer513]

The YZ250F is the toughest of that bunch, but don't expect any 250F to go as far on a set of valves as a YZ450 does. More RPM=higher number of valve closings=more rapid wear. Simple arithmetic.

[rmcr250r]

All these two stroke guys have me brain washed into thinking 4 strokes are unreliable POS, then i think about my yz450f and how everything is in spec after 60+ hrs of mostly dusty mx tracks.Then those same two stroke guys are the ones changing their topends every 40hrs and sending the cylinder out to be replated. One of my friends actually spent $1500 on fixing his grenaded 09 ktm200xc. (talk about irony)

[Family Man]

As far as I have seen the YZ450f's are in a league of their own. Very dependable. I have hundreds of hours my original 07 head. Change the oil often. I've replaced the piston and timing chain. I did have the water pump fail and the kickstarter seal. Oh and my clutch cover warped, clutch abuse.

[Steel Panther]

All these two stroke guys have me brain washed into thinking 4 strokes are unreliable POS, then i think about my yz450f and how everything is in spec after 60+ hrs of mostly dusty mx tracks.Then those same two stroke guys are the ones changing their topends every 40hrs and sending the cylinder out to be replated. One of my friends actually spent $1500 on fixing his grenaded 09 ktm200xc. (talk about irony)

and, they have to put a few dollars of oil into their gas!

[arnego2]

One of my friends actually spent $1500 on fixing his grenaded 09 ktm200xc. (talk about irony)

Hi there

What happened to him? My YZ450 grenaded on me and I spend about $ 1500 on parts and labour. I had to replate my cylinder as well

Now I have a grenated Yz250 and I'm looking at about $300 to rebuild it. 4 Strokes can be more reliable when you ride at a leisure pace, surely they last quiete a long time. But the fun factor is in 2 stroke. I don't care much if a 4 stroke is faster or not. I ride about 8 hours a week and that means a lot of maintainance on any bike.

Regards

Arnego2

[sro2004]

That's real good news OP.

I have an '09 YZ450F coming up on 35 hrs. I ride track only, but rarely see the upper end of the RPM range. The motor is bone stock (including the exhaust system), and I change the oil probably WAY more than I need to (I love maintenance almost as much as riding). The bike runs like a swiss watch...3 kicks to start her when I get to the track...then 1 kick for subsequent motos. I love it. Guys in the pits are like...WTH? "Dude, you got that thing dialed". Heh...I've never even had to adjust the carb (of course I don't tell them that ).

This is my first thumper, and the first off-road bike I've had in 20 years!

It's time to start thinking about the valves and timing chain and a couple of other things. Having never worked on suspension before, I changed out my springs about 20 hours ago (thanks to Gray and ShockDoc (Doug Harvey) for the input), and am super satisfied with how the forks and shock are performing (although at 235 lbs, I really should try a revalve to find out how much better it could be).

If I can handle disassembling and reassembling the forks, I should be able to check my valves and replace a timing chain.

I know the valves absolutely MUST be checked...but at 35 hours, should I bite the bullet and go ahead and do the timing chain? If so, OEM or aftermarket? I want only the very best for my bike...

I've also re-greased swingarm, linkage, shock bearings, and plan to do it again soon.

Can you guys give me some additional ideas of what preventative maintenance I could/should do at this point? I'd appreciate it.

OP, thanks for posting!

[arnego2]

Hello there

I think about 50 hours is the time to change the time change if you ride it hard. Time chain plus tensioner. But I also believe you will see if you need to change both items once you feel the tension of the chain when checking valves. When I changed my cam chain I felt a difference. When it is overripe to change is when you see that the change sticks somehow when you turn over the engine.

The difference is felt best when pulling the tensioner, the old chain I was able to pull it over the intake sprocket. Kinda slack, for the new one I had to undo and move the whole cam shaft to get the new one in.

You are lucky to like maintaining as much as riding, I prefer riding by about 80%. Admittedly to own the right tools enhances greatly the fun factor in maintenance.

Regards

Arnego2

[rmcr250r]

What happened to him?

Powervalve broke completely ruining the cylinder,piston, crank, and bottom end bearings.

Edited September 23, 2010 by rmcr250r

[arnego2]

Hi there

uff yeah the powervalve is quiet expensive. Luckily the hould about 8 to 10 years. Hard to see it before too. Sorry to hear that.

Regards

Arnego2