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the_artist

indestructible

13 posts in this topic

138 hours, I changed the piston for the first time. You read that well! 138 hard ridden hours and hardly any wear at the skirts. Plus the valves were right in the sweet spot specs-wise.

Well here's the story: Coaxed by previous experience of Yamaha 's reliability I decided to bypass the ridiculously low hours piston change interval and to trust my ears and my rear end. I've been ultra tight with oil and filter change schedule, and with air filter cleaning as-well. I also used nothing but top-shelf synthetic oil. (Please trolls, no debating the clutch slippage B.S.:p)

So she run perfectly fine until this week I started noticing a slight decrease in torque and was experiencing a bit of flameout during hard deceleration. So I thought the time had come. I had all the parts already at hand just in case so I got the bike to my mechanic's. A couple of hours later, he called me back, flabberghasted: almost no sign of wear in that motor, about the amount he usually sees on 30-40 hours bike from other manufacturers. the piston was out of specs but ever so slightly...

The main cause for the loss of torque and flameout was in fact a worn spark plug!!!

Now just so you guys know, I don't putt around... I ride mostly motocross on a perfectly prepped super-fast track with a couple of free-revving sand sections so this pup has flirted with the red line many times. And at 138 hours, it's probably been panic-revved for a full hour !!!!:smirk:

So maybe one day I'll experience the dreaded and proverbial 3K four stroke rebuild but as long as I'm on a YZ it just seems like a distant thought. like some frightening story old riders tell around the campfire to scare the young mini racers...

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138 hours, I changed the piston for the first time. You read that well! 138 hard ridden hours and hardly any wear at the skirts. Plus the valves were right in the sweet spot specs-wise.

Well here's the story: Coaxed by previous experience of Yamaha 's reliability I decided to bypass the ridiculously low hours piston change interval and to trust my ears and my rear end. I've been ultra tight with oil and filter change schedule, and with air filter cleaning as-well. I also used nothing but top-shelf synthetic oil. (Please trolls, no debating the clutch slippage B.S.:p)

So she run perfectly fine until this week I started noticing a slight decrease in torque and was experiencing a bit of flameout during hard deceleration. So I thought the time had come. I had all the parts already at hand just in case so I got the bike to my mechanic's. A couple of hours later, he called me back, flabberghasted: almost no sign of wear in that motor, about the amount he usually sees on 30-40 hours bike from other manufacturers. the piston was out of specs but ever so slightly...

The main cause for the loss of torque and flameout was in fact a worn spark plug!!!

Now just so you guys know, I don't putt around... I ride mostly motocross on a perfectly prepped super-fast track with a couple of free-revving sand sections so this pup has flirted with the red line many times. And at 138 hours, it's probably been panic-revved for a full hour !!!!:smirk:

So maybe one day I'll experience the dreaded and proverbial 3K four stroke rebuild but as long as I'm on a YZ it just seems like a distant thought. like some frightening story old riders tell around the campfire to scare the young mini racers...

That's about the same scenario I found on my 01 wr 250 with over 300 hrs. The ring had only worn 1/3 of the spec range. That's why I have an 09 yz450 with over 400hrs without a rebuild. Some think I am crazy,stupid etc. but these motors are like an old XR motor. They are extremely reliable with proper maintenance.

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my 400 hasn't needed a valve adjustment in 13 years. it doesn't get trashed on, but it's no garage queen either. the adjustment gets checked every so often, but it's not going anywhere out of spec it seems.

i wish i could say the same for my 250f, but the top end on that went rather quickly...

i feel the big bore yamaha motors are bullet-proof. good thing they are otherwise i'd be on a 2t.

Edited by CRF100biker

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264 hours on my '08 and I still have not pulled the head off of it. Fires up first kick most of the time and runs like a champ.

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138 hours, I changed the piston for the first time. You read that well! 138 hard ridden hours and hardly any wear at the skirts. Plus the valves were right in the sweet spot specs-wise...

I assume your ride is the bike in your sig, a 2010yz450? Thinking about getting one of those. (or a 2011)

Good to know.

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My 2001 is on stock everything except head gasket. Not sure of the hours, but the previous owner wouldn't have known how to check valve clearances if his life depended on it. To him cleaning the air filter was doing everything anyone could ever dream of doing in terms of maintenance.

I checked the valves a month or so ago and they're still dead on.

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To him cleaning the air filter was doing everything anyone could ever dream of doing in terms of maintenance.
:smirk: Been there, done that... My parents were hippies, no tools were to be found anywhere near our house when I grew up so I pretty much taught myself the basics when I got my first bike... Now I work on my my clutch, bearings, brakes, pretty much everything except the motor wich I could probably do but I get so easily distracted that I just don't trust myself.

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I assume your ride is the bike in your sig, a 2010yz450? Thinking about getting one of those. (or a 2011)

Good to know.

You won't regret it, this is an awesome bike.

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You won't regret it, this is an awesome bike.

Picking it up, and riding it, tomorrow! I can't wait.

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Buddies 08 WR450 has over 3000kms on nothing but tight single track goodness. He changes his old/filter regularly and puts in a new sparkplug from time to time and that's about it. I just changed my top end out on the 06 YZ450 last winter and cylinder wear was minimal and cross hatching was clearly still visible, and I made an adjustment to the valves only to put them on the loose end of spec. These are awesome (but noisy :smirk:) engines considering their complexity to other brands.

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These are really solid motors! Be sure to keep up with valve clearance and leak down checks, etc as the time adds up. The center intake valve on my '07 YZ450 went at roughly 200 hrs. Shimmed it once at about 20 hrs and it stayed in spec 'til the coating wore through. Went from spec clearance to sticking open in just over 10 hrs. Considering that 2/3 of the 200 hrs was in the often heavy dust of D37 desert scrambles I'm happy with 200 hrs.

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... the often heavy dust of D37 desert scrambles ...
Ever ride D38? That's dust right there. To be any finer it would have to be a gas.

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