YZ267F Lives!

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#1
Just tore down my YZ250F with 20 hrs of hard abuse on it to install a 2mm overbore kit I got from Eric Gorr. Everything looked extremely good. No measurable wear on piston, rings, cylinder, or cams. Valves were spot-on, rod and crank are holding together fine. I run only Mobil 1 15-50w except during break-in. I'm very happy with the way this motor is holding together so far. No, I haven't had a chance to ride the 267cc kit yet. I'll post my opinions when I get enough time on the bike to have anything useful to say. I'm sick of those guys who say "...well I rode it up the driveway and boy does it rip". I don't find that kind of information useful. I will be dissapointed if I can't tell any difference, but I ride this bike for every pony it's worth, so I'm expecting a noticable increase, and 2HP is all I'm looking for right now. :p

Mark

'01 YZ267F
 
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#2
Looking forward to the review, I down with Eric for the 267 in a month or so. looking for more low to mid, should be the ticket.
 

steve125

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#3
Yea man i can't wait to do mine! Bashn is 2mm over all Eric will go? I was hoping for a least 3mm over without having to go to a steel liner and i don't want to do that. Also did you have an option with the piston choice as far as compression goes?
 
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#4
17cc is that really worth all the money? it cost like $400 doesnt it. I wouldnt spend that much money if it doesnt do very much difference. But sure im a poor kid. Maybe i also gonna spend that kind of money on crap i never use when im 30 but i hardly think so!
 
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#5
Originally posted by pyromaniac
17cc is that really worth all the money?
It's not the displacement that makes the difference as much as the change in intake velocity, torque peak rpm , and the changes to the squish/quench area. There is more than meets the eye going on here :)
 
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#7
What was the verdict on the Thumper racing 290 deal? Just looking through some old mags the other night and ran across an article on it, but haven't heard much more since.
 
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#8
Originally posted by Scott in KC
What was the verdict on the Thumper racing 290 deal?
Those braintrusts stuck a STEEL sleeve in it. :scream: NUFF SAID.
 

bud

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#9
"It's not you, it's me", where have I heard that before? :)

I'm thinking about a wr250f as a 2nd bike, while my riding buddies are trying to convice me I'd be beter off on a 426 as I'm nearly 200 pounds geared up. My theory is that I'll be faster and less tired if I can keep the throttle wide open more often. I love the power of the 426, but I'm far from convinced I'd be able to ride it hard for a full day. The 250 seems like a good compromise, at least on many of the tight trails we ride, but I haven't had the chance to test ride one yet. At least I'm reasonably sure my next bike will be a yamaha four stroke :).
 
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#10
This overbore phenomen is making me crazy.

No matter how new bike you guys have you still "need"(atleast you say so) it faster. I think its bs but anyway. So what do you do? Well you own the latest yzf400, after one week you buy a 426 bigbore for alot of $$$. Why didnt you buy a 426 in the first place?

No matter how new and how big bike you have you always think you need more? Do you have some kind of obsession of making mods? Or rather a obsession of spending money on your bike, no matter if you need whatever you buy or not.
 

Vic

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#11
Originally posted by pyromaniac
Do you have some kind of obsession of making mods? Or rather a obsession of spending money on your bike, no matter if you need whatever you buy or not.
Is that a rhetorical question?
 
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#12
No matter how new and how big bike you have you always think you need more?
Not true - the aftermarket industry doesn't sell much for the 426 that really gives it more hp (the bolt-on crap doesn't help).

Reason why? Even the best riders found out the 426 has more than adequate power for most lowly humans.

So why do 400 owners purchase the 426cc kit? They find the same thing that Yamaha did - that extra 26cc's actually smooths out the power delivery and makes the bike deliver power that is a little more manageable.

The 250 is a different story. I'm a dork, but I REALLY like the stroked 250. Why? Same reason some riders find it easier to ride a 250 than a 125. That extra torque is sure forgiving when I'm in the wrong gear on a hill!

Am I pushing the WR250 for all it's worth? Heck no! But in some cases, the CORRECT application of more hp or torque will make a bad rider better.

Oh yea, and there's always the guys with more dollars than sense. To them it's just an ego boost - mine's bigger than yours - The aftermarket industry LOVES these people!
 
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#13
pyromaniac, I would have to agree there is little to be gained by pumping a YZ426. Power was never an issue with that machine. I took a risk and spent $400 for a Yoshi pipe on my YZ250F and it was the best money I've ever spent on a bike. It added 2-3 HP, but more importantly, it added great throttle response. Now I've taken a chance on adding 17cc, increasing my compression ratio to 13.2:1 from 12.5:1. Why is this so important to me? Because I race at 5200ft altitude! Increasing the compression ratio increases low RPM performance. The combination of the pipe, displacement, and 13:1 CR should give real-world gains that will compensate for power lost due to my high altitude. So why not just go back to a 426? I'm much faster on a lighter bike regardless of horsepower, and it's just more fun to race. That's why I'm pumping a few dollars into my "old" bike rather than buying something new. I could easily go "backwards " replacing this bike.:p

Mark

'01 YZ267
 
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#14
Rich,

What's the down side of using a steel sleeve? Does Eric use these in his big bore kits?...Thanks, Bill
 
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#15
Different thermal expansion coefficients, poor heat transfer, softer and shorter lived than a plated cylinder, probably not re-borable because of thin wall, etc. etc.

Mark
 
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