YZF267 v. YZF290

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#1
I'm looking for input from YZF 250 owners that may have direct experience of the relative merits
of Eric Gorr's 267 overbore or the Thumper Racing 290 overbore.

I know this subject has been touched on before in the broader spectrum of overall performance
upgrades for the bike, but I'd like to hear more about these specific modifications. I'm looking for
an overall power gain, but with an emphasis on the low to mid-range.

Also, I've heard that Thumper uses a steel sleeve in their kit. Is this true and if so, is there really
as big a drawback to that as one would logically assume, or does it work OK?
 
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#2
C'mon, I know there are people on this board that can
give me educated answers to these questions.
Do I need to know a secret handshake or something?
Pretty please?
Hello? Bueller? Anyone?
 
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#3
Putting a steel sleeve in a YZF250 F is an IDIOTIC caveman approach and a generally foolish thing to do. Either go with a plated barrel 267 or wait till the proper plated aluminum sleeves are available to go to a bigger bore.

Feel better now? :)
 
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#5
So what is it you wanted?
Did you want someone to tell you it's OK to put a steel sleeve in a 250F?
It's NOT.

The rest of the info you seem to be looking for was covered pretty completely just a couple of weeks ago. The SEARCH function can provide the specific links.
 
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#6
Gee Rich, I really didn't come here to be scolded.
I merely thought I could pick the brains of some intelligent people.
Forgive me if I was wrong.
Sorry to have bothered you. Thanks for your help and have a nice day.
BTW, go easy on the caps lock. It's really not polite to shout.;)
 
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#7
oh well....

you'll have to fogive Rich for the scolding...he's still trying to figure out why
he doesn't have Ed Scheidler's job after "correcting" his "wrong" comment
on not running race fuel in a YZF....LOL!!!
 
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#8
You seem to be taking this personal and it's not. You asked a question and I gave you an accurate answer.
Your concerns about using a steel sleeve in a design like this are well founded. I get really annoyed when companies who are considered "qualified" do brain-damaged work and try to pass it off as a some great engineering feat. My disgust with what these companies are doing to these engines probably comes off as overly caustic towards YOU. That wasn't my intention at all, but experience has shown me that making a strong statement about these types of things is the only way to truly get the point across. Any other tactic and people will be e-mailing for months asking "should I put a steel sleeve in my 250F?".

As I've pointed out in previous threads IMHO these engines can benefit from a slight bore increase if your goal is to shift the the torque peak to a lower rpm range. I'm not convinced at this point that the increase to 290 (even with an Al sleeve) is a good idea unless you are willing to trade a lot of high rpm efficiency for a torquey woods bike type powerband. Changes to the cylinder head, cam timing and ignition curve would be required to retain the same rpm capability as the stocker with a bore increase of that magnitude. I haven't seen evidence at this point to make me believe the cylinder head will ever be up to the task.

Proper squish clearance, appropriate fuel, and good jetting is all that is really needed to realize this engines true potential. A 2mm overbore just makes the bike more friendly for those of us with less than stellar skill levels. My advice is to wait till you need to freshen up the top end unless you are a racer who truly needs every advantage.
 
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#9
Re: oh well....

Originally posted by grunk250r
.he's still trying to figure out why
he doesn't have Ed Scheidler's job after "correcting" his "wrong" comment
on not running race fuel in a YZF....LOL!!!
Blind Faith in OEMs their reps or anyone else is naive.
 
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#10
Rich, that was EXACTLY (sorry for yelling) the info I was looking for.
Thank you (really).
Sorry we had to play Tom Sawyer and Huck Finn to get there. I apologize for being overly sensitive.
Another hot day with no A/C in my office:p
I'll be racing the 250F in the 30+ and 40+ Expert classes against 250/Open bikes, so I am looking for a "racer's edge" although I should probably just work on my reducing the size of my waistline before I worry about increasing the size of my piston:D
Aren't message boards great? :cool:
 
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#11
Originally posted by Indy92
I'll be racing the 250F in the 30+ and 40+ Expert classes against 250/Open bikes, so I am looking for a "racer's edge" although I should probably just work on my reducing the size of my waistline before I worry about increasing the size of my piston:D
On short tight SX type tracks it will likely be an advantage, on longer tracks you would probably be better served blueprinting the stock setup.
 
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#12
Indy,

Keep us posted. I have a friend that traded his 426 for it's baby brother and races the Vet B class. He rails and if he could get a little better start, he'd be winning the four lap "sprint" motos.

vetwfo'er
 
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#13
vetwfo'er , I will let you know how I make out with the lil' thumper.
I currently run in the top 3-5 in my class, but hanging on for a whole moto is my biggest problem.
I ride and train when I can, but (as with most guys my age) working for a living keeps me from making
the real strides in the fitness area that I'd like.
I've ridden the 250F and find it much less tiring to ride than my CR250 and that's my primary reason
for making the switch. Not to mention that it sounds way cool.

And Rich, if you're still out there, I just dug out a copy of Dirt Bike with a test of the Thumper Racing 290F.
Don't you find it particularly contemptible that they would "forget" to mention the fact that Thumper uses a
steel sleeve? When discussing the sleeve in the article, they never mention what the sleeve is made from.
I can't believe that they didn't know. I think that stinks.
 

TwinSpar

AssClown WannaBe
N. Texas SP
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#14
Indy,
You come from a background similar to mine (bike, age(don't know that one for sure), fitness level, etc)... You will love the BabyF. I didn't believe the whole "no arm-pump" theory until I got on the bike. It is a joy. When I first got on the bike and rode I thought "It's slow". Little did I realize that the slow feeling was not having to fight to hang on. It's competitive with the group of big bore bikes that I ride with.

I will be looking at the EG work when I have the $'s.
 
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#15
Don't you find it particularly contemptible that they would "forget" to mention the fact that Thumper uses a steel sleeve?
They wouldn't know what a steel sleeve was unless it came up and bit them in the backside.

They only regurgitate what information the engine builder feeds to them. Like mamma birds (i guess that leaves us, the reader, as the baby birds eating that crap!).

Sorry, was I sarcastic? Excuse me, I've been writing product releases all day - I'm grumpy.