CR250???

[SQUIRLEYMOFO]

??????cr250

Everyone wants they're 02 up CR to have a YZ like powerband. Why? (lowend I know) Why does the case reed KTM work so well? is the case volume the key? and why did KTM switch to a smaller carb? Also on a side note they are geared the same 13/48. Does the 250SX need race fuel? I think I druther figure out what KTM did to their motor than Yamaha. I probably would have a KTM, but don't care for the rear suspension/higher price of parts/availabilty etc...Thoughts? Also they share the same bore and stroke.

 

[SQUIRLEYMOFO]

Oh well guess the question was to hard.

 

[robwbright]

Its a bit hard to answer 5 or 6 questions in one post, especially when they're rambling . . .

Try to restate it more clearly and I'm sure someone will help you out.

Your questions are outside my range of experience and knowledge, tho.

 

[SQUIRLEYMOFO]

Fair enough why does a case reed KTM rock and a stock case reed CR suck? and I love the CR just not the motor.

 

[skipn8r]

Everyone wants they're 02 up CR to have a YZ like powerband. Why?

In my case, I like having snappy engine response over a wide RPM range so that I can handle odd-spaced rolling whoops and sandy hill-climbs at a variety of engine speeds. It adds flexibility.

 

[oldfrt613]

I think everyone gets a bad taste in their mouth with the CR power because the jetting is so far off stock. The YZ on the other hand is almost jetted perfect from the get-go. I like my CR powerband for moto, I'll take the YZ power for trail riding though - which do most of the bikes get used for, that's right trial riding, so it is only natural that the YZ motor is perfered by most. The CR seems to be geared more towards moto guys who will spend some time setting them up for moto, Yamaha however has the pulse of the majority of riders who want a bike that just works out of the box.

 

[john3_16]

Everyone wants they're 02 up CR to have a YZ like powerband. Why? (lowend I know) Why does the case reed KTM work so well? is the case volume the key? and why did KTM switch to a smaller carb? Also on a side note they are geared the same 13/48. Does the 250SX need race fuel? I think I druther figure out what KTM did to their motor than Yamaha. I probably would have a KTM, but don't care for the rear suspension/higher price of parts/availabilty etc...Thoughts? Also they share the same bore and stroke.

Well the first question you answered yourself..

They are just two different motors with different specs even though they both take in fuel though the cases...Obviously, stock the KTM works better and there's more to it than just bore and stroke...Different porting specs, different powervavle, different intake, maybe a more balanced connecting rod, bearings, different cases, and the list goes on.

It's like asking why the 03' KX250 was so much weaker than an 03' YZ250 even though they are both cylinder reed motors.

Or maybe a better example would be the RM250 and YZ250...Suzuki pretty much copied Yamaha's motor but the YZ is still stronger with a dyno curve that stronger at nearly every rpm level...Why even though the motors have almost identical specs ?

 

[22703]

hey squirleymofo did you get the varner cylinder fixed yet?if you did let me know what you think.

 

[SQUIRLEYMOFO]

Well the first question you answered yourself..

They are just two different motors with different specs even though they both take in fuel though the cases...Obviously, stock the KTM works better and there's more to it than just bore and stroke...Different porting specs, different powervavle, different intake, maybe a more balanced connecting rod, bearings, different cases, and the list goes on.

It's like asking why the 03' KX250 was so much weaker than an 03' YZ250 even though they are both cylinder reed motors.

Or maybe a better example would be the RM250 and YZ250...Suzuki pretty much copied Yamaha's motor but the YZ is still stronger with a dyno curve that stronger at nearly every rpm level...Why even though the motors have almost identical specs ?

The RM and the YZ are similar........the SX and the CR are night and day....

 

[Rider 007]

The RM and the YZ are similar........the SX and the CR are night and day....

After speaking with Eric Gorr (and I believe he has posted some of this on DRN) it's a matter of porting and PV design.

I haven't seen any evidence of the "crankcase volume" theory touted by MXA as being the culprit. If they are so firm in their beliefs, why don't they offer up volume measurements of each of them?
Eric says that the KTM PV design is far superior to the CR system.

My CR doesn't have the grunt my YZ has at the bottom but it is plenty fast and very smooth and controllable. I can ride it for long periods without tiring from fighting it.

:ride:

 

[SQUIRLEYMOFO]

After speaking with Eric Gorr (and I believe he has posted some of this on DRN) it's a matter of porting and PV design.

I haven't seen any evidence of the "crankcase volume" theory touted by MXA as being the culprit. If they are so firm in their beliefs, why don't they offer up volume measurements of each of them?
Eric says that the KTM PV design is far superior to the CR system.

My CR doesn't have the grunt my YZ has at the bottom but it is plenty fast and very smooth and controllable. I can ride it for long periods without tiring from fighting it.

:ride:

me too I am old and fat I'll admit that. But it pisses me off to get beat in a drag race on dirt road by a 02 SX125 that chapped my hide. He's a good friend and lightweight, but has little to no dirt experience.

 

[Rider 007]

me too I am old and fat I'll admit that. But it pisses me off to get beat in a drag race on dirt road by a 02 SX125 that chapped my hide. He's a good friend and lightweight, but has little to no dirt experience.

Then perhaps something else is wrong.

While my 03 CR250 doesn't have the bottom end of my 02 YZ250, it will absolutely run with it in a straight line. Getting it running cleanly made a big difference.

I've never had a 125 or 250F beat it in a drag race.

:ride:

 

[jrm]

If your CR is getting beat in a straight-line drag race by a 125, you've got a problem with your bike. Could be jetting, PV cable adjustment or worn rings, but there's no way that should happen.

 

[SQUIRLEYMOFO]

If your CR is getting beat in a straight-line drag race by a 125, you've got a problem with your bike. Could be jetting, PV cable adjustment or worn rings, but there's no way that should happen.

It has no more than 10 hours on it.It was bought last October as a leftover. Cable is adjusted per article on the web ( it helped) Air cleaner is good, new plug, V-force reeds no air leaks.....little or no spooge. I really like the bike just doesn't run the way I expected.

 

[SQUIRLEYMOFO]

What's weird is it ran better rich, just fouled plugs and din't want to start. Keihin is in the mail trying that next. I have a Varner motorsports ported cylinder next. Oh and Turbo Blue from now on.

 

[22703]

let me know how you like it when you get your cylinder back.or did you send it out?

 

[oldfrt613]

You should have 10+ hp on a 125, something is afoul.

 

[skipn8r]

You should have 10+ hp on a 125, something is afoul.

Agreed. My son ('05 CRF250) and his ride buddy ('05 YZ125) were both afraid of getting my bike in the power band before I had the cylinder ported. Now they won't touch it. Assuming you're opening the throttle and shifting right, you should not get beat by any 125....

 

[motometal]

The '02 CR had a weak motor, in my opinion. The '03 on up runs stronger. I still think of that MXA article saying it had "weak low end power" every time I lug up a steep hill in 2nd or 3rd gear (on my '03). I've always thought it was a great running motor, once it was jetted and geared.

The Eric Gorr Mo Better port and head work made it run more like the KTM, power bottom to top with a better over-rev.

It may not run quite like a YZ or KTM, but then I like my chassis and the general feel of the bike a lot better.

I think you need to test ride a similar CR for comparison, it might answer a question or two, before you keep throwing money at it to try to make it something it isn't.

 

[sandflyz]

I had to put way more than 10 hours on mine before o could really asess what i thought i needed to do.
#1one you have to jet it propery
#2 get a aftermarket reed block
#3get Eric to port it
#4 take it out for a test spin wipe out and bust 3 F****** fingers and then park it for a while :bang: