CR250 build

[travis.hudson.77]

Thinking of building a 03-05 CR250, i know that they had a fairly smooth motor........do any of you guys know if [with porting you can make these motors hit like the kx's, rm yz? Any help would be appreciated, motor builders who specialized in these?

[motoman356]

if you can  find an 01 motor. they werent case reed engines which had issues and not as powerful as the 01 engine. but porting and polish reeds pipe will bring in mo power and builders can generally adjust the engine delivery

[Jeram]

Thinking of building a 03-05 CR250, i know that they had a fairly smooth motor........do any of you guys know if [with porting you can make these motors hit like the kx's, rm yz? Any help would be appreciated, motor builders who specialized in these?

the snapping "comming on the pipe" has very little to do with porting (and definitely not polishing!).

its all in the pipe and the power vale.

but keep in mind that coming on the pipe hard is not necessarily a symbol of faster. it just means that it has a torque curve which has no gaping holes in it.

Although there are some gains to be had via porting, generally the 2000+ CR's are already fairly good so you will only gain a couple hp here and there throughout the range depending on what you do.

[metal_miracle]

This is from personal opinion and what 2 stroke tuners have said..


Its that the crank case on 02+  had a too much crank volume, compare to the older models.

and that the power band that honda vent for whit the crank case motors.  resulting in a no bottom, no top end power curve


If motor is broken i would get an older engine  2001 and downwards

[tweetakt]

I have an 03.  All I did was pipe, reeds, and jet kit.

The thing really rips.  When it hits the power you better be holding on.   
Not much bottom, good top end,  tons of mid.  I used to think it felt electric untill I rolled my KTM.

[Stusmoke]

dogger recently made a series of threads on here about a similar build. I think his was an 01 I'm not sure though. If you've got deep pockets I'd talk to him. Actually talk to him anyway he knows his stuff. Then again alot of people on here do.

Other than that basically what Jeram said. My 01 CR125 uses some fancy ass doo dad that controls how open the exhaust ports are at certain RPM I'd wager the 250s use the same thing. I can't speak for whether or not its tuneable. Other than that, slap on a pipe jet it to perfection grab some reeds and rev it too the moon. Do all that and it should hit you with enough force to sit you on your arse

[Jeram]

the PV controller is made by companies such as Zeeltronic.

but unless your modifying your motor theres not much point.

just keep the mods simple and enjoy your reliable, mid range powerhorse of a motor!

[oppenheimer77us]

I would choose a 2005-2007 model CR as a starting point, the last incarnation of the CR model. This bike has many strong points; light weight, it's an excellent neutral handler, has good suspension, and is just a blast to ride. My 2006 is bone stock engine wise with the exception of an FMF fatty and silencer, v-force reed and a JD jet kit and I like these mods.

I am in the process of a build on this 2006 CR250R for moto and have done a lot of research on what other folks have done with the engine setup (the common complaint with late model CR's was the lack of bottom end snap and inability to properly jet the stock Mikuni). I have come to the conclusion that the best mod is to replace the stock mikuni with a keihin PKW airstryker 38 and this will be my next purchase. I'm starting to regret the money I've already spent on the mikuni at this point. When I rebuild the engine I'm also going to have some cylinder/head work done and bump the compression a bit. This is probably all I'm going to get done and with the other mods should be all the engine I will need.

[travis.hudson.77]

Thanks Guys! This is all very useful, the last two stroke i had was a 05" yz 250 and before that a 03' KX 250 that i raced in the A class......but i thought the Honda would be a fun one to build, im done with 450's.

[Stusmoke]

I would choose a 2005-2007 model CR as a starting point, the last incarnation of the CR model. This bike has many strong points; light weight, it's an excellent neutral handler, has good suspension, and is just a blast to ride. My 2006 is bone stock engine wise with the exception of an FMF fatty and silencer, v-force reed and a JD jet kit and I like these mods.

I am in the process of a build on this 2006 CR250R for moto and have done a lot of research on what other folks have done with the engine setup (the common complaint with late model CR's was the lack of bottom end snap and inability to properly jet the stock Mikuni). I have come to the conclusion that the best mod is to replace the stock mikuni with a keihin PKW airstryker 38 and this will be my next purchase. I'm starting to regret the money I've already spent on the mikuni at this point. When I rebuild the engine I'm also going to have some cylinder/head work done and bump the compression a bit. This is probably all I'm going to get done and with the other mods should be all the engine I will need.

Thanks Guys! This is all very useful, the last two stroke i had was a 05" yz 250 and before that a 03' KX 250 that i raced in the A class......but i thought the Honda would be a fun one to build, im done with 450's.

Please post up a thread on your build with photos, we all love reading custom jobs

[travis.hudson.77]

I sure will i have been waiting along time to build a bike just the way i would want it,....when i was racing i never had more than what my sponsors would provide, but now that im in a better place i can finally get the goodies i drooled over! I will keep you guys updated.   

Travis.

[captmoto]

All this info came from Thumpertalk from some pretty knowledgable guys.
.025 to .030 milled from the base of the cylinder or have RB Designs or Eric Gore mill the head for pump gas. The squish is way to big for pump gas. Milling the cylinder will give more bottom endand correct the squish volume without messing with the head.
Keihin Air Striker carb. I got mine from CarbPartsWarehouse and it came with the correct 03 carb cable. You can use a carb from a late model YZ250. The difference is the back to front length and fitment but it's not a problem either way. Either carb you won't be running the TPS.
The stock pipe seems to be the way to go with a PV Shorty on it but I am running a full PC set-up because my CR had a crushed leaky pipe.
Race gas unless you can get non ethanol gas or 50-50 to handle the slight boost in compression. I run avgas 100LL with no problems. I was running 100 street racing pump gas but it was almost $10 a gallon. Avgas is $5.50
These mods will get the bike running way better, probably the way it was intended to run but this is plenty for most people.
Good luck and keep us posted. It's cool to see whats up with other peoples CR250's.

 

[riffraff]

It's cool to see whats up with other peoples CR250's.

Someone stole mine last month 

[conbread]

 i know my buddy has a 04 cr250 and it has a bastard carb on it.. one of the best mods is to swap it over to the YZ style carb... we cant get the plug to clean up like the one in my YZ..

[travis.hudson.77]

Thanks guys! I picked up a stock 04' today!!! I will post pictures soon when i start the build! Can't wait!