359 replies to this topic

[shrubitup brap]

I have stock front springs of 02 CR250. Prolly 50 hours use. Mailed cheaply to you.

[achap TT Silver Member]

btw... CamP... congrats on the new bike... I'm in the process of reviving my 02... so much fun!!!

[nitrojoe TT Bronze Member]

i actually just picked up one of these from a friend of mine. original top end. just got an fmf gnarly on it. head is being shipped off for milling, and im looking into carbs. i already have some experience with the kihein pwk from my ktm 200. do you have to use the carb from an early 2000s yz250? i saw those ones have a throttle positions sensor. can the connectors from the yamaha carb be spliced to hook up to the honda system and work well also? my biggest question is does it have to be a carb off an older yamaha, or could i get a carb from jd jetting like this one. http://www.jdjetting...page=1

this kit looks like a good deal. would this yeild the same results as the tps equipped carb you are using, or is there some special magic wizard in the tps equipped carb that makes it work better?

[frdbtr TT Gold Member]

nitrojoe, on 17 April 2012 - 11:03 PM, said:

i actually just picked up one of these from a friend of mine. original top end. just got an fmf gnarly on it. head is being shipped off for milling, and im looking into carbs. i already have some experience with the kihein pwk from my ktm 200. do you have to use the carb from an early 2000s yz250? i saw those ones have a throttle positions sensor. can the connectors from the yamaha carb be spliced to hook up to the honda system and work well also? my biggest question is does it have to be a carb off an older yamaha, or could i get a carb from jd jetting like this one. http://www.jdjetting...page=1

this kit looks like a good deal. would this yeild the same results as the tps equipped carb you are using, or is there some special magic wizard in the tps equipped carb that makes it work better?

The carb from JD Jetting is longer then the Yamaha carb but will work. It is basicly the carb from a 2000 cr250 with JD's Jet kit. installed. My guess is that you will have to remove the sub frame to get it on.

[SMarquez TT Gold Member]

frdbtr, on 18 April 2012 - 05:05 AM, said:

The carb from JD Jetting is longer then the Yamaha carb but will work. It is basicly the carb from a 2000 cr250 with JD's Jet kit. installed. My guess is that you will have to remove the sub frame to get it on.

Yes on the sub frame but once it's done you can do jetting changes without removing the tank and seat to remove the carb top. Read CamP's posts as he has done all the carb testing if you are using a YZ250 carb. The carb is the single best mod you can make. Mine runs really well and I haven't even checked my squish yet. Cam and I are both running 100 octane gas though.

[CamP Get Help Now]

nitrojoe, on 17 April 2012 - 11:03 PM, said:

i actually just picked up one of these from a friend of mine. original top end. just got an fmf gnarly on it. head is being shipped off for milling, and im looking into carbs. i already have some experience with the kihein pwk from my ktm 200. do you have to use the carb from an early 2000s yz250? i saw those ones have a throttle positions sensor. can the connectors from the yamaha carb be spliced to hook up to the honda system and work well also? my biggest question is does it have to be a carb off an older yamaha, or could i get a carb from jd jetting like this one. http://www.jdjetting...page=1

this kit looks like a good deal. would this yeild the same results as the tps equipped carb you are using, or is there some special magic wizard in the tps equipped carb that makes it work better?

I got a '00 YZ250 carb off ebay for $67. All '00-up YZ250 carbs fit the 04-07 CR250 perfectly. I plugged the powerjet, re-jetted it and decided not to use the TPS because when it is disconnected, the ignition reverts back to a standard ignition curve, which I believe works better than the 3D ignition map.

The JD carb will work, but it's 16mm longer than the stock Mikuni, so it's sort of like stuffing 10lbs of potatoes in a 5lb sack.

Rather than mill the head to reduce the squish, I milled the base of the cylinder .030". This corrected the squish to .050", reduced the port timing, and increased the cranking pressure from 215psi to 235psi. Note that the added compression requires 100 octane fuel.

These mods resulted in one of the best 2-stroke motocross engines that I've ever used.

Edited by CamP, 18 April 2012 - 06:32 AM.

[ben williams TT Bronze Member]

My friends 04 has a Mikuni, but does not have any wires coming from it. Can youz guyz give me any clues as to figure out what year carb it may be? Trying to figure out where to set the floats and I see 8mm some years and 14mm some years. Also bought a JD jet kit for an 04 and do not know if it will work in his properly.

[tjb531 TT Bronze Member]

GREAT Thread! I want to clarify, these mods will work on the 02-04 CR250Rs? Measure the squish, and mill the base of the cylinder to achieve .050, right? Get a properly jetted PWK carb and shred?

After years of making payments on 4-strokes i'm now in the market for a two stroke. If these mods can make the Honda run like the Yamaha then i'll be riding red!

[CamP Get Help Now]

tjb531, on 19 April 2012 - 09:38 PM, said:

GREAT Thread! I want to clarify, these mods will work on the 02-04 CR250Rs? Measure the squish, and mill the base of the cylinder to achieve .050, right? Get a properly jetted PWK carb and shred?

Yes, before doing any machine work, you should measure your squish with lead solder to determine what you have. The 05-07 CR250's all seem to come stock with .080" of squish, so milling .030" off the base is all that's required to get the proper .050" of squish. I haven't worked on a 02-04 so I can't confirm how much squish those bikes have from the factory.

[CamP Get Help Now]

ben williams, on 18 April 2012 - 01:20 PM, said:

My friends 04 has a Mikuni, but does not have any wires coming from it. Can youz guyz give me any clues as to figure out what year carb it may be? Trying to figure out where to set the floats and I see 8mm some years and 14mm some years. Also bought a JD jet kit for an 04 and do not know if it will work in his properly.

That's odd. The 04 Mikuni should have a TPS on it. Post up a pic and maybe we can tell you what it is.

[erik_94COBRA TT Bronze Member]

tjb531, on 19 April 2012 - 09:38 PM, said:

GREAT Thread! I want to clarify, these mods will work on the 02-04 CR250Rs? Measure the squish, and mill the base of the cylinder to achieve .050, right? Get a properly jetted PWK carb and shred?

After years of making payments on 4-strokes i'm now in the market for a two stroke. If these mods can make the Honda run like the Yamaha then i'll be riding red!

The squish on my '03 CR250 was 0.065" stock. With the thinner base gasket from an '05-'07 CR250 the squish was 0.055".

So, after turning down your cylinder base you would have to have the head cut/relieved or else you'd have more compression than desired (too little squish).

[BlackCR25098 TT Silver Member]

CamP, on 18 April 2012 - 06:30 AM, said:

I got a '00 YZ250 carb off ebay for $67. All '00-up YZ250 carbs fit the 04-07 CR250 perfectly. I plugged the powerjet, re-jetted it and decided not to use the TPS because when it is disconnected, the ignition reverts back to a standard ignition curve, which I believe works better than the 3D ignition map.

Dude, is the carb you bought the Keihin PJ? Like what's on my 98 cr250? If not, I have never heard of another carburetor that has a actual "powerjet" and eletric TPS just like mine...I guess what I'm asking is, should I do the same to mine? I hate that it has the electrical TPS powerjet. Just something that will break and makes it less reliable.

What I'm wondering, is how exactly do I bypass the powerjet and unplug the TPS? I think Eric Gorr mentioned simply putting in a different needle or something but wanted to get your experienced opinion...Would I have to do anything with the ignition or other electronic parts? What are the pro's of the standard ignition curve with it all unplugged and bypassed vs. with it in?

Very interesting to hear that other carbs use this same design. I figured they used it 2 years on the CR (97-98) and trashed it because it's obviously not the best design. I also hate how my idle adjustment IS the choke knob..

[hallsy TT Gold Member]

BlackCR25098, on 22 April 2012 - 01:25 PM, said:

Dude, is the carb you bought the Keihin PJ? Like what's on my 98 cr250? If not, I have never heard of another carburetor that has a actual "powerjet" and eletric TPS just like mine...I guess what I'm asking is, should I do the same to mine? I hate that it has the electrical TPS powerjet. Just something that will break and makes it less reliable.

What I'm wondering, is how exactly do I bypass the powerjet and unplug the TPS? I think Eric Gorr mentioned simply putting in a different needle or something but wanted to get your experienced opinion...Would I have to do anything with the ignition or other electronic parts? What are the pro's of the standard ignition curve with it all unplugged and bypassed vs. with it in?

Very interesting to hear that other carbs use this same design. I figured they used it 2 years on the CR (97-98) and trashed it because it's obviously not the best design. I also hate how my idle adjustment IS the choke knob..

FWIW the PJ carbs that came on the 97'- 98' CR 250 do not have a TPS (Throttle Position Sensor), they do have a power jet though.

[BlackCR25098 TT Silver Member]

hallsy, on 22 April 2012 - 06:09 PM, said:

FWIW the PJ carbs that came on the 97'- 98' CR 250 do not have a TPS (Throttle Position Sensor), they do have a power jet though.

Okay I got confused because I read somewhere and thought that my electric power jet and a TPS are essentially the same thing. It monitors certain RPM's and does something, but I'm sure what we're both talking about here is very similar.

[mynewcr250 TT Silver Member]

BlackCR25098, on 23 April 2012 - 10:04 AM, said:

Okay I got confused because I read somewhere and thought that my electric power jet and a TPS are essentially the same thing. It monitors certain RPM's and does something, but I'm sure what we're both talking about here is very similar.

the power jet is RPM dependent.. a jet that is solenoid actuated by the ecu. there is no throttle position sensor.

the throttle position sensor is just that, it lets the ecu know the throttle position which is used for power valve timing.

[BlackCR25098 TT Silver Member]

mynewcr250, on 23 April 2012 - 05:22 PM, said:

the power jet is RPM dependent.. a jet that is solenoid actuated by the ecu. there is no throttle position sensor.

the throttle position sensor is just that, it lets the ecu know the throttle position which is used for power valve timing.

O ok well either way isn't it also popular to "bypass" the power jet on these PJ carbs also? I saw eric gorr mention it so I figured it would be of benefit, plus it takes away the electric piece that will eventually break, thus making it more reliable without it.

[Ricky7 TT Member]

My friend found a brand new 03! He paid $4,300 for it. It really was brand new! But there's nothin like a brand new 07.

[BlackCR25098 TT Silver Member]

Ricky7, on 25 May 2012 - 09:24 AM, said:

My friend found a brand new 03! He paid $4,300 for it. It really was brand new! But there's nothin like a brand new 07.

How is that even possible in 2012? LOL but that is flipping awesome. I'd be worried about a built motor that's been sitting for 9 years. They say the absolute worst thing for a motor is to sit, but I'd sure love an 02-07

[Ricky7 TT Member]

I know, he had a friend search the nation for him! I let you know if he sells it he hasn't ridden it yet just been tricking it out for the trails over here!

[BlackCR25098 TT Silver Member]

Ricky7, on 26 May 2012 - 04:49 PM, said:

I know, he had a friend search the nation for him! I let you know if he sells it he hasn't ridden it yet just been tricking it out for the trails over here!

Has he even fired it up? I'm guessing it's never had premix in the tank...A brand new 03 in 2012, that is hard-on material right there... I almost wouldn't even wanna ride it. The thing about having even a "like new" condition bike that's ridden hard, is you know it's gonna get destroyed and dirty soon, but that's what makes it so respectable, atleast for me. Almost like how girls love flowers, because they know they're going to wither and die...sort of.. I know the popular belief is "it's a DIRT bike so I ain't gonna wash it or nothin'" cuz I'ma real core rider, but there's something so nice about a clean bike (between track days) that goes right along with keeping it perfectly functioning, and it sure as hell ain't hurting anything. Brings out the haters though, that's for sure.

Tell your boy to fire that sucker up and welcome her to 2012, and would definitely get a hr. meter installed before the first kick for perfect timing.