Eric: Mo Better/265 '03 CR250 Questions

[skipn8r]

Guys,

I have an '03 CR250 that is in excellent, stock condition. I've added a Doma pipe, VF3 cage and 38 mm PWK. I bought the bike knowing that it is a bit soft down low and up top compared to a YZ250 or a 250SX. I would just buy a YZ250, but I know and understand Honda suspension, etc., and would rather stick with Honda. I'm considering the Mo-Better porting and maybe the 265 to get it as close as possible to the YZ250 or 250SX powerbands.

For reference, I'm 160 lbs, I ride mostly desert, off-road and some MX track at 5,000 ft elevation. All of it is recreational riding. I'm coming off a 250 4-stroke and I really like the 2-stroke snap, but I'd prefer less of a sudden hit and a more broad power band. I'd also prefer to be able to run on 91 octane pump gas.

I'll probably buy a new cylinder and head for you to modify and keep my stock parts on hand. Questions:

1) Will any other year CR250 cylinder/head bolt up to an '03?
2) If so, which year is preferable as a starting point?
3) If I buy new parts, should I just buy a cylinder and exhaust valve assembly, or a specific cylinder and separate exhaust valves?
4) Can you characterize how much "better" the 265 with Mo-Better is compared to stock displacement with Mo-Better?
5) Does the 265 setup have more to do with an improved exhaust valve configuration and seal than it does a displacement increase? (No trade secrets, please.)
6) Does anyone know why KTM can get an awesome, broad power curve with a case-reed 250 while the current case-reed Honda seems to produce such a narrow powerband?
7) Anything else I need to consider?

Thanks.

EDIT: I reposted this over in the Mods and Performance forum which is where I suppose this should have been.

 

[SQUIRLEYMOFO]

Excellent questions I'm in the same boat.....just bought a "new" in stock 2003 CR250 myself..........I'm picking up a 50 tooth rear sprocket Saturday. Then likely a Kiehin Carb. I'm going watch this thread closely.......

 

[pace]

My Mo-Betta '03 CR250 comes on harder than any stock displacement 250 I've ridden. That's probably accentuated by the relatively weak bottom end, but it does pull into the powerband much quicker than the lazy-feeling stocker. The midrange is simply awesome, and it signs-off a little later than stock too.

I also have the PWK, but I have the Rad-Valve and a PC Shorty Silencer. I also had Eric raise the compression to help offset the effects of altitude a little. These three things combined probably contribute significantly to the stronger bottom-mid transition than I've seen on other ported late model CRs.

 

[SQUIRLEYMOFO]

On a side note skipn8r where did you get your Doma pipe? I understand they're the best for the CR. California is the only place I've seen them listed........I'd don't mind mail order, but would like to see one before I lay down $265.

 

[skipn8r]

I read about the Doma in a Dirt Rider test and got mine from Langston Racing. I actually put it on before my first ride on the bike, and worked on jetting the bike with the PWK. After getting a good jetting baseline, I ran some back-to-back exhaust comparisons between the stock pipe and the Doma. It certainly seemed to me that the Doma was noticeably better off the bottom; like when rolling on out of a corner. I didn't have much space to compare the top end differences, but at worst, they seemed similar.

I bought the Doma un-plated and it looked very high quality; nice welds. I went ahead and had mine plated locally (just to prevent corrosion) when I found out it was mild steel. It bolts on a little easier than the stock pipe.

When considering my opinion, also know that I'm new to 2-strokes, so I don't know how much a pipe should affect the powerband.

 

[SQUIRLEYMOFO]

I read about the Doma in a Dirt Rider test and got mine from Langston Racing. I actually put it on before my first ride on the bike, and worked on jetting the bike with the PWK. After getting a good jetting baseline, I ran some back-to-back exhaust comparisons between the stock pipe and the Doma. It certainly seemed to me that the Doma was noticeably better off the bottom; like when rolling on out of a corner. I didn't have much space to compare the top end differences, but at worst, they seemed similar.

I bought the Doma un-plated and it looked very high quality; nice welds. I went ahead and had mine plated locally (just to prevent corrosion) when I found out it was mild steel. It bolts on a little easier than the stock pipe.

When considering my opinion, also know that I'm new to 2-strokes, so I don't know how much a pipe should affect the powerband.

In theory the shape of the pipe is everything for a 2 stroke.........some aftermarket pipes just don't live up to their claims, and the factory pipe is a good piece. Especially considering you can get the cylinder ported cheaper, and it should make a bigger difference. Guess I'm about to find out.....can't believe I thinking of pulling a bike apart that's still on it's first tank of fuel! :blah:

 

[2-stroke diehard]

I am new to the '03 CR250R myself. With my Pro Circuit Works pipe, PC shorty silencer and UNI filter, I already feel the bike is very strong and I have no problem riding it as is, especially with 100 octane race gas (running more than 100 octane would probably be too much and could actually HURT HP). I wouldn't dream of running less than 93 octane, consider how few hours you spend on your bike, and the tiny 2 gallon tank, it's well worth it to run at least a mix of race and pump gas IMO.

As for the 265 kits, etc, I'm all ears, someone please shed some light on these subjects. :nod:

 

[skipn8r]

Guys,

I have an '03 CR250 that is in excellent, stock condition. I've added a Doma pipe, VF3 cage and 38 mm PWK. I bought the bike knowing that it is a bit soft down low and up top compared to a YZ250 or a 250SX. I would just buy a YZ250, but I know and understand Honda suspension, etc., and would rather stick with Honda. I'm getting close to buying the Mo-Better porting and probably the 265 to get it as close as possible to the YZ250 or 250SX powerbands. I'll probably buy a new cylinder and head for you to modify and keep my stock parts on hand.

For reference, I'm 160 lbs, I ride mostly desert, off-road and some MX track at 5,000 ft elevation. All of it is recreational riding. I'm coming off a 250 4-stroke and I really like the 2-stroke snap, but I'd prefer less of a sudden hit and a more broad power band. I'd also prefer to be able to run on 91 octane pump gas.

Questions:

1) Will any other year CR250 cylinder/head bolt up to an '03?
2) If so, which year is preferable as a starting point?
3) If I buy new parts, should I just buy a cylinder and exhaust valve assembly, or a specific cylinder and separate exhaust valves?
4) Can you characterize how much "better" the 265 with Mo-Better is compared to stock displacement with Mo-Better?
5) Does the 265 setup have more to do with an improved exhaust valve configuration and seal than it does a displacement increase? (Not looking for trade secrets, just perspective.)
6) Does anyone know why KTM can get an awesome, broad power curve with a case-reed 250 while the current case-reed Honda seems to produce such a narrow powerband?
7) Anything else I need to consider?

Thanks.

PS: I originally posted this over in the 2-stroke forum. I suppose it ought to be here.

 

[Eric Gorr]

Hi Skip,
The 2002-04 top ends interchange but the 03 is the best design stock. Its best to just port the stock cylinder because the cylinder is very thin and boring it oversize makes it less reliable but its a cheap fix if the bore ever gets trashed from a broken ring.
The difference in the KTM is its 15 years newer than the Honda. The exhaust valve system with the triple exhaust combined with low and wide transfer ports is the key. Remember the 2002-04 CR250 engine is actually an older generation than the previous 1992-2001 engine. The 2002 CR250 originated as a dual sport bike in Japan in 1988.
If you like the KTM then buy a KTM because no amount of money is going to make the 2003 CR250 the same as the KTM.
Good luck, Eric

 

[skipn8r]

Thanks Eric. I suppose I'll stay Red for now and see if Honda brings out any new 2-strokes or let's them die. I'll be buying a new cylinder and head to ship off soon. Thanks again.

 

[+30]

03 cr 250

Im in the same boat, vet rider 03 cr250 vforce,gnarly,shorty.blah blah bolt-ons valving blah blah :blah: I wanted to get the mo-better deal, and will be sending a cyl within a month. I had to put the *&$ gnarly pipe on to get any bottom, but it signs off way early and kind of leaves you hanging off of bigger jumps if the runup was deep or loamy and you couldnt afford to upshift. Id like to try the doma, heard good things about it. My question was about milling the head, have heard that this bumps up compression, and causes you to have to use higher octane. I dont mind using only race gas (c-12) (u-2) (mr2) or other but was wondering about the benefit, can it actually be felt on the track?

 

[skipn8r]

My Mo-Betta '03 CR250 comes on harder than any stock displacement 250 I've ridden. That's probably accentuated by the relatively weak bottom end, but it does pull into the powerband much quicker than the lazy-feeling stocker. The midrange is simply awesome, and it signs-off a little later than stock too.

pace,

Thanks for the observation. I've read your post several times to make sure I understand what you've said. In my perception (and remember, I'm 2-stroke ignorant), what I'd refer to as the mid-range hits really hard on my bike as it is. It's a bit sluggish down low (not terrible) and seems to flatten a bit early on top. I'm not sure I want any more mid-range hit as what I currently have is pretty aggressive in the first 3 gears. If I could change anything, I'd give up some mid-range hit to broaden things out some; for some more bottom and top. Still contemplating....

 

[Barbarian]

skipn8r,
Welcome to 2-smokes. Unfortunately, it's hard to get all that "hit" out of the midrange. I used to do it on my old style cr250s by adding an extra spring to the powervalve. That was the only thing that really smoothed out the hit, for me.
But I'm a 4-stroke guy now, so maybe I should just be keeping my mouth shut!!

 

[skipn8r]

barbarian,

I'm coming off 4-strokes and I really just like that 2-stroke snap. Can't seem to get the same rush on the 4-strokes I've ridden (CRF250R, CRF450R, YZ450F, etc.). I just need to smooth a few rough edges and I think I'll have fun with this thing. Anyway, if you haven't already, you should ride a new YZ250. Pretty nice powerband; even compared to a 4-stroke :nod: .

 

[sandflyz]

03 CR Mo-Betta

I have a 03 cr myself and am getting ready to send my top end to Eric for Mo Betta everywhere. I read in one of the posts in this thread that the top engine mount has to be drilled out as the porting often includes having to mill the head or cylinder to compliment the porting. I'm wondering if this has to be done for an engine that runs strictly on pump gas. Increasing compression might cause detonation issues for me. As well, i would prefer not to have to round out an engine mount hole if it could be avoided. If anyone has anything to say i would appreciate it.

 

[skipn8r]

As I understand it, most CR250 porting involves lowering the cylinder (I could be wrong) which means something in the mounting system needs to be modified to accommodate. At any rate, you need to modify the two plates that connect between the frame and the engine head; not anything on the engine itself. A 3/8" rat tail file and a vice would do fine.

 

[mtk]

Eric Gorr ported my 2002 CR250 and I didn't have to modify anything on reassembly.

 

[X men]

Hi Skip,
The 2002-04 top ends interchange but the 03 is the best design stock. Its best to just port the stock cylinder because the cylinder is very thin and boring it oversize makes it less reliable but its a cheap fix if the bore ever gets trashed from a broken ring.
The difference in the KTM is its 15 years newer than the Honda. The exhaust valve system with the triple exhaust combined with low and wide transfer ports is the key. Remember the 2002-04 CR250 engine is actually an older generation than the previous 1992-2001 engine. The 2002 CR250 originated as a dual sport bike in Japan in 1988.
If you like the KTM then buy a KTM because no amount of money is going to make the 2003 CR250 the same as the KTM.
Good luck, Eric

Eric,

What was then the actual reason that Honda introduced a "new" engine in 2002 ? If this design is older, where is the gain for honda ? I know that in 2001 it was commonly said that the honda had an old engine, but to replace it with an even older engine...

Peter

 

[X men]

Hi Skip,
The 2002-04 top ends interchange but the 03 is the best design stock. Its best to just port the stock cylinder because the cylinder is very thin and boring it oversize makes it less reliable but its a cheap fix if the bore ever gets trashed from a broken ring.
The difference in the KTM is its 15 years newer than the Honda. The exhaust valve system with the triple exhaust combined with low and wide transfer ports is the key. Remember the 2002-04 CR250 engine is actually an older generation than the previous 1992-2001 engine. The 2002 CR250 originated as a dual sport bike in Japan in 1988.
If you like the KTM then buy a KTM because no amount of money is going to make the 2003 CR250 the same as the KTM.
Good luck, Eric

I think the marketing guys at honda will be very pissed off to see that despite the gag-orders given to the motor press, somebody is bringing out the age of their engine :-)

Concerning the KTM, is the actual gain of a mo-better porting on the KTM as important as it is on the honda ?
An what is your opinion on the fact that ktm decreased the diameter of the carb to 36 in stead of 38 on the 05 model ?

Thanks in advance for your reply
Peter

 

[skipn8r]

Eric Gorr ported my 2002 CR250 and I didn't have to modify anything on reassembly.

My engine mouting plates were a tight fit before mods. Maybe mine is odd.

 

[Masterphil]

An what is your opinion on the fact that ktm decreased the diameter of the carb to 36 in stead of 38 on the 05 model ?

I hear that the KTM is tough to improve on in the mo-better sence, besides setting up for race fuel. But if you want to move the power to a different RPM range, that's a different story.

They are still trying to tame the beast that they created a couple of years ago. It seems as though KTM likes to make an absolute ripper of a motor on the top end, then find out what they can add to smooth out the power without decreasing peak. They are still trying to tame the 125 as well, It gets more bottom every year.

 

[X men]

It is true that the 250 was an animal when the latest generation engine came to the market. They worked hard to "tame" the beast. But i am hesitant to believe that the decrease in carb diametor is a good choice, or even a choice with the ultimate goal as to achieve a softer power output. To be honest : i think they got a good deal from keihin for buying the 36 that no other company is buying . Off course i could be wrong, but the thought crossed my mind héhéhé.
I hope that Eric will share his thoughts on this matter with us.

For the 125 : this is by far the best 2 stroke engine, way more usable power then their competitors. I read an article from a dutch 2 stroke specialist who said that the reason for the superiority of the 125 ktm is in the advanced powervalve system (compared to the japanese 125's) and in the use of a long conrod. The same article said that only the yamaha 125 also had a very modern designed cylinder portmap.