Taming 01 cr250

[nicodemus]

:bang: I have an '01 Cr 250 with a nasty hit I'd like to mellow out. The bike is all stock except for a rad valve. I'm a novice MX rider (riden mainly trails) & am usually on tight/hard pack tracks trying to keep the thing from exploding under me. Personally, I don't care if I lose anything on top; I don't spend much time there anyway. I know of porting, flywheel weights & pipes, but am looking if other options exist. I've also used suggested jettings, with no luck, too rich or too lean. I'm @ 30 pilot, 2 sizes leaner needle, & 410 main @ sea level in warm Texas weather. Anyone have any suggestions? If I can't get this mellowed I'm also thinking of looking into a '01 Cr 125. Something I can keep on the pipe on a tight track. Anybody have one?

-Jason

 

[+30]

could you trade for a smelly crappy 4 stroke? -kidding ---you could overpack your silencer i guess and ride with the choke on let the air out of tires. sorry just had to knock the pins down........I have a 03 cr 250 and it has no bottom. the 01 has a good solid bottom so the gnarly pipe wont do much to mellow out the hit i dont think on the 01, it will however kill the top like you said. I would think eric gorr would have some ideas, you may want to try a jd jetting kit lots of cr riders use them. I didnt spend enough time to get mine dialed, but those guys say they are great. Other cr owners who couldnt get their carbs dialed went the kehin route carbpartswarehouse.com there is a lengthy thread on the kehin conversion. do you already have the flywheel weights on the bike? they make a huge difference, even an aftermarket clutch with steel plates is noticeable in and out of corners. if that doesnt do it loosen up the spark plug,,---kidding...dont try that one. :rotfl:

 

[mx547]

If I can't get this mellowed I'm also thinking of looking into a '01 Cr 125. Something I can keep on the pipe on a tight track.

if you're having trouble riding a bike with a wonderful engine like the '01 cr 250, you'll really be in trouble trying to keep a 125 on the pipe. just keep practicing on the 250, soon you'll be glad you did.

 

[CRguyStan]

You can save your parts money and drive to PA where I will trade you my nearly new 03 CR250 for your 01, because I miss that midrange hit. The 03 is more like a more torqued up 125 in my eyes.
Stan

 

[nicodemus]

Crguy thanks for the offer, but PA is bit too far. Ok, I deserved the ribbing, I'm just frustrated, some of it is that I'm coming off a smelly, crappy yz 400F. I wanted to go to a 2 stroke, rode a friends yz125 & liked how light it was, but I had the throttle pinned most the ride & could see wanting more soon. I went with the 250 & had read the 01 Cr was the bike to get & luckily a guy with an 01cr wanted a 400f. I think I may have a jetting prob, the bike has no power down low, then little over half throttle it explodes but is not exactly usable power, it's pretty much like a light switch. I want to try a flywheel weight, but don't see how it could help if I have no real throttle control. I didn't notice the bike acting like this before (but was on a longer/wide turn track), only the last few times I've had it out where I need some throttle control. I've gone through the carb, float is set, jets are clean, air filter is good, reeds are good, the piston visually looks ok & plug is tight :laugh: . I do want to get through this though, I really like everything else about this bike, just frustrated. Eric Gorr sound like a good guy to talk to, thanks guys. Jason

 

[CRguyStan]

Jason,
I forget the details, but I know I went one notch leaner on the needle and milled an extra 1mm off the backside of the slide on my 01. It prettymuch was snappy throughout with a very strong mid, not like a 97 motor, but deserving of apprecitation. I went from that to my 03 which is jetted correct and has the power, but with the case reeds is far flatter on the bottom-mid, which I think is mainly from the servo powervalve.
Play with the jetting and the mods and you will be on track, this bike should come on strong out of the gate with stock porting.
Stan

 

[Faded]

Jason,

Your description of the power leads me to believe that the bike has a problem that is not uncommon with these bikes. It sounds like the exhaust valve is stuck part way, or fully open.

When people do top-ends on these bike they don't realize that they need to line up the crow's foot actuator arm on the bottom of the cylinder with a corresponding arm on the crank case. The result is the actuator arm gets pinched (and ruined) and the exhaust valve is rendered inoperable and the bike has a powerband much like you've described.

The easiest way to check is to pull the 17mm round cover off of the left hand side of the cylinder. Underneath will be a shaft that looks like the head of a flat blade screw. On the cylinder surrounding the cover there should be two markings, an "L" and an "H". At idle and lower RPMS the flat notch in the shaft should point at the "L", when you rev up the motor the shaft should turn and the flat notch should point at the "H". If the shaft does not rotate when you rev the bike then you have a problem that needs to be fixed.

Hope this helps.

 

[nicodemus]

Thanks guys, checked the pwr valve movement today, all good. Is it normal to have spooge behind the 17mm cover? and coming out while the bike is running with the cover off? My spark plug was pretty wet (surprised it starts) & I appear to be real rich now, I didn't think the slight change in temps would mess with the bike this much since according to the manual, I'm already lean, but I'm guessing the black wet plug doesn't lie. I guess it makes sense, I was probably loading up down low & then once it leaned back out BANG instant wheel spinning power. Does my theory sound right to you guys? Thanks for your ideas, I'm going to play with the pilot circuit & install the s-7 nozzle for now, if I can't get it, there’s always the 00 carb to try. Thanks, Jason

 

[bikepilot]

I absolutely love my 01' CR250R and I primarily ride it in the woods. Motor is stock save FMF exhaust (Fatty style, came with the bike). I'd suggest you spend your $$ getting in more practice. It will be much easier and more fun to learn how to handle the motor than to turn it into a 4-t.

The bike is super-sensitive to jetting. A 20°F diff can be the difference from too rich to too lean. Last summer I was running a 410 main, 32.5 pilot, S-7 nozzel, stock needle and it was pretty good at 65-75° and sealevel. Now that the temps are down its noticeably lean (went for a gentle trail ride).

If you are not having trouble with keeping it on the pipe, but only wheelspin, then perhaps a flywheel weight would be a good idea. I ran one on my old KX250 and my laptimes improved for the better, even on an open MX track.

For the record I'm a B class rider in HS or MX, but spend more time on HS.

 

[RTT]

if your bike is mechanically sound, maybe think about using a "G2" throttle- it's made by 'sam wanckett', and used by lots of 'fast' guys,.. it basically offers three throttle 'cams' , which gives the rider a greater amount of 'control' on acceleration; sounds like this may be helpful to you-i've been 'testing' with this during the fall '05 and found very good results under wide changes of traction. best luck, jack

 

[ellandoh]

im wondering , do you have it set up with the proper tire for the hardpack youre riding?? if not , first things first you know :nod:

 

[nicodemus]

Different Tires may help; this place is kind of like riding on marbles once the tilled soil dries out. I'm going to slap a fly wheel weight on & try to get my jetting in line, thank for the advice though, there are so many things to take into consideration, its nice having these forums. Jason

 

[steve.emma]

hi there, if you are having problems with excessive midrange hit then why are you so lean on the needle? a ragged harsh type power is often caused by a too lean mixture, just because the plugs looks rich at idle doesnt mean its too lean at 3/4 throttle. maybe try going middle clip or even richer and see if that takes some of the sting out of it.