250F yz big bores ?

Any one in here have big bore on there two stroke. 265, 285, 295
How do you like it? Downsides?

I'm thinking of building a Eric Gorr 265 but wonder if it's worth the money for 15cc
I want to go 265 to stay legal for racing.
 
Well seems like ossi likes his 265, that got me thinking about WR gears as well :thinking:
You might want to think about that one. I rode a custom built KX250 with a 300 kit and a WR tranny and geared for high speeds. It was built by Team Green so it had a lot of motor work done, but I felt you had to shift too much with the WR tranny to get the motor in the sweat spot, even with a heavier flywheel. I would say (and this is just me, so take it as you will) that you should play with gearing first after the 265 kit is done and maybe a flywheel adjustment before going out and installing the WR tranny....But again that is just me..
 
You might want to think about that one. I rode a custom built KX250 with a 300 kit and a WR tranny and geared for high speeds. It was built by Team Green so it had a lot of motor work done, but I felt you had to shift too much with the WR tranny to get the motor in the sweat spot, even with a heavier flywheel. I would say (and this is just me, so take it as you will) that you should play with gearing first after the 265 kit is done and maybe a flywheel adjustment before going out and installing the WR tranny....But again that is just me..
You have definatly got a point. I have made the mistake of modding to much stuff all at one time before.
Makes it hard to figure out whats doing what.
 
Put me in the "it's a lot of cash for 15cc" department. That said I can see of situations where I would do it. For example if the cylinder needed replating, then it would seem to make a lot more sense.
 
I use a YZ 2nd ,3rd and 4th. !st and 5th are WR.
I had the full WR transmission in my 01.

My 265 is just great for me in the hills and forest up
here. I am 187 pounds right now and really have all
the power I could use. I have hit the desert with this
one but have not gone Monster Climbing as of yet.

I can say I rode this bike back to back with a YZ 450
and the pull was different but no greater then each other.

Once again I post
the rough calculation; 0.12 HP per CC for a 4t, 0.2
HP per CC for a 2t. Both of these being modern
correctly jetted motors.

So you can have a Gorr YZ 300 2t at 60 HP by calculation
or a YZ 543 4t at 65 HP by calculation. I would run the
gear box as stated above in my 265.

Since we are spending Spies Dollars he should build both
and meet us at Jawbone so we all could test them:banana:

All that said I am a 2t guy, but would love a 4t for the desert.
 
Carl,

I would have said the same before I rode one, that said I would do a 285.
I bought this at 265.
 
I use a YZ 2nd ,3rd and 4th. !st and 5th are WR.
I had the full WR transmission in my 01.

My 265 is just great for me in the hills and forest up
here. I am 187 pounds right now and really have all
the power I could use. I have hit the desert with this
one but have not gone Monster Climbing as of yet.

I can say I rode this bike back to back with a YZ 450
and the pull was different but no greater then each other.

Once again I post
the rough calculation; 0.12 HP per CC for a 4t, 0.2
HP per CC for a 2t. Both of these being modern
correctly jetted motors.

So you can have a Gorr YZ 300 2t at 60 HP by calculation
or a YZ 543 4t at 65 HP by calculation. I would run the
gear box as stated above in my 265.

Since we are spending Spies Dollars he should build both
and meet us at Jawbone so we all could test them:banana:

All that said I am a 2t guy, but would love a 4t for the desert.
Dude you pull 60hp out of a YZ300 motor and sign me up...I had a built KX500 that was putting 63HP to the ground and that was some serious brute power...

When you guys get all these 265, 285, 295, etc motors put together, let me know so I can meet you out in the dez with my cleaned up YZ250 and see how they compare..:ride:
 
Dude you pull 60hp out of a YZ300 motor and sign me up...I had a built KX500 that was putting 63HP to the ground and that was some serious brute power...

When you guys get all these 265, 285, 295, etc motors put together, let me know so I can meet you out in the dez with my cleaned up YZ250 and see how they compare..:ride:
There is hp and then there is torque. A 500cc two stroke will have way more torque in the low revs than a high strung 300. Like any other engineering decision it is a trade off. My choice is big bores and gobs of low end torque.
 
There is hp and then there is torque. A 500cc two stroke will have way more torque in the low revs than a high strung 300. Like any other engineering decision it is a trade off. My choice is big bores and gobs of low end torque.
Agreed, but I still love the sound of a good tuned and geared 250 2 stroker pinned across the desert and blipping the throttle when cresting a nice little hill that has a killer drop off on the other side and floating back to the desert floor and then back on the gas hard....:smirk: Oh Crap, I need to go have a smoke now :devil:
 
Those are calculations paraphrased by the engineer that did the Yamaha motor.
General rules of thumb. Both my 250 and 265 would smoke my old
MX 400 and YZ 400, neither would out climb the old bikes. The 265 may
not be that far off, then again I have not been to Jawbone or invader with it
so that is speculation.:blah::blah::blah::blah::blah::blah::blah::blah::blah:

I do admit If I was riding nothing but desert a would opt for the 543.:smirk:
 
Thanks for the advise guys, a few months ago I picked up a parts bike(blown crank and cylinder needs replating) So I have this motor sitting on my floor begging to be built into somthing fun. My current stock motor runs great, so really I'm in no hurry. I figured I could build the spare piece by piece, as $$$ IS an object.

Anyone need parts for an 02 yz 250? Ive got pretty much everything except motor and wheels.You will get a good deal and be helping to finance my big bore:thumb:
 
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