2004 cr250r how do i crisp this thing up boys??

[rydethahillz]

I just sold the 08 crf450 and went back to the 2strokes guys.. i picked up and 04 cr250 and i need some advice on these motors. Im not ignorant but i had an 01 that ran flawless and i had an 02 and it was kind of a dog compared to the 01. Different motors inmany ways, but there has to be a way to get this 04 to run clean right.. help me out guys... this thing still had the original top end in it by the way and the carb is completely stock settings wise.. wont idle, little sluggish through bottom and into mid.. top felt very strong though. I dont want to dump a bunch of money into metal mulisha stickers, just want a solid reliable motor to blast around on.. thanks ahead of time for any help at all!!!

Im in phx, az by the way,

420

32.5

2nd position

1 1/2 turns

in the process of replacing the top end and clutch as of now...

[kevin yarrington]

I am working on a 2004 myself. Bottom is a dog but very good mid to top. I went to a 27.5 pilot and it cleaned it up a little but I am at about 2 1/2 turns and dont want to drop the pilot anymore. I just ordered a JD jet kit and hope the needle is the ticket. On mine, the top end looks great, carb is clean, new correctly oiled filter but it smokes to much for me. I really don't know anything about the R/C valve but it is clean. If I get the kit in this weekend I will give you an update.

[brentk660]

I bought a mint 03 with original top end and about 30 hrs on it. I couldnt get the thing to be consistent on jetting to save my life. It would be great one day and crap the next. I ordered the JD jet kit. It helped some but still was never happy with the power.

I then bought a used 38mm A/S Kehin and the thing came alive. Best mod out there in my opinion over that crappy mikuni carb. It bolts right in, jets easy and runs crisp. You can find them used for 125$ or so on ebay, and I sold my Mikuni for 130$, so it was a wash.

Jetting:

Seattle area, 200-3000ft

172 main

stock 99 cr250 needle (1370)in middle clip

45 pilot

2turns on the air screw

Hope this helps

[MX926]

My 04 in the summer time 70-80 degrees

Main-420

Pilot-30

Needle- stock clip at the top

Air Screw 1.5 turns out

I run power 110 race gas, stock pipe, pc shorty silencer. Super crisp, very snappy. Alos tighten your powervalve cables, be sure they are snug, any slop will make it feel as though your jetting is rich.

If you polish all the rough casting spots out of the carb it helps teh carb to perform better. Also swap out the stock exhaust flange for the boysen flange, and you will get that added bottom end you are looking for.

[dvorak51]

Remove and clean the carb. thoroughly,your pilot jet is plugged.I have an 03 thats touchy to temp.and humidity change.It runs very good between 65 and 80 with a 410 main 32.5 pilot clip at 2nd and air screw from 1.5 to 2 out. My top end is stock with vforce3 reed assembly and an FMF SST pipe with a power core 2 shorty.I have to run 110 octane to avoid detonation.MX926 tell me about the boyesen exhaust flange.Where is it most noticable? I have been thinking about installing one.

[rydethahillz]

ive actually been reading alot about the kehin carbs and it seems like alot of people suggest that.. in all honesty i feel like we should be able to make these mikunis work, but if i cant adjust it to do what i want ill probably go that route.

[MX926]

"MX926 tell me about the boyesen exhaust flange"

The boysen flange matches the shape of the cylinder exhaust port perfectly. And makes a smooth transition for the exhaust into the exhaust pipe itself. It gives more throtle response right off the bottom.

The stock flange is a very rough transition, it actually doesn't match the shape of the exhaust port at all. Its more round, and the port is oval shaped.

[Monts]

I've read about a lot of jetting issues with the Mikuni on here. I've never had an issue with the Keihin, it seems spot on all the time at 180/42 for me. I see them on Ebay for around $80 fairly often.

[mcdirtclod]

My brother-in-law picked up a new-in-the-box 2004 CR250 last year. Most of the magazine tests dissed the motor for soft low-end, but rated everything else top-notch. In reality, unless you're a pro or really fast amateur, it has more than enough stock MX-type power. But, since we can't ever leave well-enough alone ... after researching multiple back-issues and dozens of online impressions and experiences, we've settled on the following combination of bolt-ons: Add a tooth to the rear sprocket. Slightly lower gearing really helps coming out of corners. Install the JD jet kit - spooge and smoke has all but disappeared. Get one of the Boyesen exhaust flanges while you still can. If you don't think it will make a difference, take off the stock one and look at the shape of the exhaust port - the port is D-shaped (laying on its side) and the stock flange is round! This is an uncharacteristic engineering oversight or manufacturing shortcut (at least for Honda) - I'd estimate 30% of the area is mismatched. The Boyesen flange is a work of art and matches the port shape exactly. The Pro Circuit Works pipe with the 304 shorty silencer generally gets the highest marks for this bike, but honestly, it's more for the bling factor. As many have mentioned, the stock pipe is actually pretty good. Finally, we added the Boyesen RAD valve with the Pro Series reeds. I have to say, this combo works. The bike is now an absolute beast, and feels nothing like the stock motor. It went from mellow and smooth but strong to a real eye-watering arm-stretcher. It pulls hard and clean right off the bottom and my brother-in-law's only complaint now is the difficulty he has keeping the front wheel on the ground. I've been doing this a long time, and I don't know if I've ever gotten such dramatic results from only bolt-ons. It's enough faster that he's finding the need for suspension re-valving - he thought it was fine at first.

[H4L]

My brother-in-law picked up a new-in-the-box 2004 CR250 last year. Most of the magazine tests dissed the motor for soft low-end, but rated everything else top-notch. In reality, unless you're a pro or really fast amateur, it has more than enough stock MX-type power. But, since we can't ever leave well-enough alone ... after researching multiple back-issues and dozens of online impressions and experiences, we've settled on the following combination of bolt-ons: Add a tooth to the rear sprocket. Slightly lower gearing really helps coming out of corners. Install the JD jet kit - spooge and smoke has all but disappeared. Get one of the Boyesen exhaust flanges while you still can. If you don't think it will make a difference, take off the stock one and look at the shape of the exhaust port - the port is D-shaped (laying on its side) and the stock flange is round! This is an uncharacteristic engineering oversight or manufacturing shortcut (at least for Honda) - I'd estimate 30% of the area is mismatched. The Boyesen flange is a work of art and matches the port shape exactly. The Pro Circuit Works pipe with the 304 shorty silencer generally gets the highest marks for this bike, but honestly, it's more for the bling factor. As many have mentioned, the stock pipe is actually pretty good. Finally, we added the Boyesen RAD valve with the Pro Series reeds. I have to say, this combo works. The bike is now an absolute beast, and feels nothing like the stock motor. It went from mellow and smooth but strong to a real eye-watering arm-stretcher. It pulls hard and clean right off the bottom and my brother-in-law's only complaint now is the difficulty he has keeping the front wheel on the ground. I've been doing this a long time, and I don't know if I've ever gotten such dramatic results from only bolt-ons. It's enough faster that he's finding the need for suspension re-valving - he thought it was fine at first.

Good right up. I had a similar experience with my 03 but took it 1 step futher & had PC do the cyl & head. It was like waking up a sleeping giant ! These bikes respond really well with just a couple of bolt ons.

[honda13]

i would agree with all of the above. but one other cheap thing you can do is add a power now valve did it on my 04 and for a $100 it was well worth it would recomend for anyone.

[rydethahillz]

mcdirtclod i appreciate the insight man.. that was a super helpful write up, and you seem knowledgable which is always good. These jd jet kits are a mystery to me.. ive heard the name alot so i started reading about them and i just dont understand what the difference is between a "jd jet kit" and purchasing a few jets from my local honda dealer. Ive always been able to clean up a bike by adjusting pretty much just the pilot, main, air screw and clip... can you explain what exactly these kits come with that makes them so helpful?

[Snipetracks]

The only thing different about the JD jet kits are the needles. The needles have a different taper typically the JD needles are leaner. The kit comes with the same main and pilot jets as you would get from Keihin or mikuni.

[mcdirtclod]

exactly - only difference is the custom taper on the needle. you can get close with different OEM needles, but it does take some trial and error - and none will match the JD taper. they are expensive, but worth it IMHO. i got an extra benefit - the kit comes with two needles - one was perfect for the 250, and the other was perfect for my 125 and with the jet assortment that was included, i was able to take care of two bikes with one kit! call JD directly - he's great to talk to and knows what he's doing. or you could just keep cleaning your spoogey silencer and number plates and changing fouled plugs...

[dvorak51]

I have a ProCircuit exhaust flange and it is also shaped perfect.I also have a PC works pipe with the r304 silencer and its killer in bottom and mid but the FMF SST and shorty has top end and overrev thats insane.Definitely add a tooth to the rear.

[rydethahillz]

Well a jd jet kit with an exhaust flange sounds like the way to go.. i appreciate the input guys.. its always nice to hear what has worked for everybody else! and im def tired of cleaning pipe spooge haha well said man. Once i get this thing back together ill post some photos, if i can figure out how thats actually done.. im a newbie.

[mcdirtclod]

i'd definitely recommend the boyesen exhaust flange. the pro circuit parts i looked at were stronger than stock - but still the "wrong" shape. they were perfectly round, and that does NOT match the exhaust port shape. here's the piece you want ... http://boyesen.com/exhaust-flange-3.html ... get one while you still can. it really works.

[Phil Hannah]

Buy extra o--rings for the Boyesen Ex flange because they dont last long. Back in 02 they were not cheap,dont know what they cost now.

[APBT]

Definitely add a tooth to the rear.

This guy can add a tooth to the front!

http://twostrokemotocross.com/2009/09/2010-honda-cr250-elsinore/

[dirtymunkey]

Concerning the carb swap. What year range is the correct Keihin carb. I am looking on ebay and I see some from 1998. Will that work also? I have seen 99 and 2000 mentioned on here but never 98. Any differences between the years?