Posts
252
Joined
2/21/2012
Location
Red Creek, NY
US
Edited Date/Time
10/3/2013 2:20pm
My son has a 2004 Honda cr250. the bore and stroke is the same as a 2005-2007 Honda CR250. They say the power curve on the 2005-07 CR250 is better. I would like to know if I can swap out the 04 cylinder to and 05-07 cylinder. Will it bolt on the 04 cases? Thanks
Actually, I'm not sure what that is for a bike, other than a 500AF. I have one, thats not it. Lol. TerryK posted that for me, after first having Justin Beiber up (asshole) a righteous female booty in a bikini (2 thumbs up asshole) and THEN it was a fucking clown (I still haven't made to Thunder Bay to kill him for that. Yet). Mines an 04 conversion.
I just had billet aluminum clutch and ign covers milled up. 25 sets. Plain, no logos,clutch has an extra 100 mil oil capacity built in. 6061 T6 material. $110 Cdn a side preferably in pairs, so I'm not stuck with oddballs. Right now I have a couple extra ign covers. Also have access to cheap laser engraving for custom logos. Let me know.
How far is Red Creek from Buffalo? That name doesn't ring a bell with me.
The Shop
I wouldn't send my stuff to PC if it was free, but that's just me. You overpay for something that any good knowledgeable local porter and engine guy can do for far less. It's not like Mitch Payton is doing the job himself. He's got a bunch of $8 an hour grunts working out back with a Dremel and a spec sheet. You are subsidizing his race efforts, to about the tune of double what you pay a good guy closer to home.
Want a fast bike with lots of snap? Advance the timing & run race fuel.
Run taller gearing to compensate for the loss of top end. Cheap and effective.... except for the race fuel!
I went the big bore route on my yz and punched it to a 285. Stock porting except the middle intake needed to be realigned and pretty high compression with a tight squish. No dissapointments with power. Just wish I did the wr450 3-5 gear swap as its way too much motor for the close ratio mx trans. Also have to be vigilant with watching crank slop as I don't have much wiggle room with the squish tightened up.
Because the Mikuni w/ TPS on your 04 is 75mm long, I would not recommend the OEM 99/00 CR250 carb or the aftermarket PWK, as they are 91mm long. These carbs are identified by a round twist-on cap. Keihin makes a 75mm long version of the PWK Air Striker carb that's the OEM carb for the YZ, SX, RM and KX250. These carbs are identified by a bolt-on cap, and they will fit your 04 more properly.
The '00-up YZ250 carb is the easiest to find used. If you go this route, you will need to epoxy shut the fuel circuit for the powerjet, then jet it like a standard 38mm PWK. A good starting point is a CEJ needle @ #4 clip, a 180 main, a 50 pilot, and the air screw @ 2 turns out. The YZ comes with a #7 slide, which is ideal for the 38mm carb. I would also recommend running it with the TPS disconnected as the 3D ignition timing map is a mess. Generally, you can find used YZ carbs for less than $100, but the downside of used parts is sometimes they are junk.
If you would prefer a new carb, the 250SX carb is a great option, especially if your goal is more low/mid power because the SX250's PWK has a 36mm bore. The body of the SX carb is casted for the TPS and powerjet, but neither feature is actually used, so you won't have to epoxy the powerjet circuit like you would on the YZ, RM or KX carbs. The stock SX jetting should also be a good starting point. You can find a new 250SX carb for as little as $272.
For the engine, the first thing you should do is measure the squish between the crown of the piston and the head's squish band. The ideal dimension for this should be .050". On my 07 CR250, the stock squish was .080" so I milled .030" off the base of the cylinder to correct the squish. This also lowered the ports and increased compression at the same time. All these things combine to pump up the low/mid power and you'll still have good over-rev if you leave the TPS disconnected because that retards the ignition timing. Eric Gorr will lower the cylinder .030" and cut the head for any fuel that you specify for only $75. I have mine set up with higher compression for 100LL avgas. Eric Gorr
Here's a link that outlines the squish band measurement process. Squish Band Measurement
The bike will run night and day better with these simple modifications.
I'd get the bike jetted right before you spend big bucks on mods...throw on a set of pipes and reeds and jet it and let it rip.
http://varnermotorsports.com/
http://www.morganracingengines.com/
http://www.hpbikes.com/index.php
Quick question, please.... On mu Husky cr125 I replaced the Mikuni 38mm TMX-X (new style) with a 36mm PWK 'shorty' from a 1999 kx125. I removed the TPS arm, epoxied the hole in the cap left by the missing arm, cut the wiring, but I left the solenoid looking thing in place as I saw no harm in it being there. I did not close the circuit for the powerjet though..nor did I remove the needle-looking metering device for the TPS. Do I need to epoxy that pwr jet hole!? How about the metering arm?
The bike runs super hard after I get past the unresponsive low end, but something doesn't feel quite right below 1/4 throttle. I've had the needle in the middle clip since day 1 (last fall), but its warmer out now, so it might be drowning in fuel at low throttle openings or could that powerjet be contributing to the problem? My 36 had a fully functional TPS system, so this has me wondering.
Also, if anyone uses RB Design's squish measurement procedure then please consider sending him the business as I dont think he made those instructions for other tuners prosperity. He'll measure the dome volume, mill the head and reset the dome volume for chump change. Decking the cylinder would cost extra, but he's more than capable. He will not port plated cylinders or work on 4-stroke heads. Period!
He's also one of my friends and I dont like him working harder than necessary to put food on other people plates.
Hope I dont sound like too much of a bitch
Thanks!
Pit Row
The 04 supposedly has the leak
The PWM is not what you want. All the OEM PWK Air Striker carbs with the bolt-on tops are 75mm long and fit the 04-07 CR250's perfectly. This includes late model SX, YZ, RM250 OEM carbs. If you want a new carb, the SX is the least expensive at $270 and the jetting should be close right out of the box. Used YZ carbs can be found for less than $100. The YZ/RM carbs require that you epoxy the powerjet circuit shut and rejet the needle, pilot and main jets for use without it. I use a YZ carb with a CEJ needle at #4 clip, 180 main, 50 pilot and air screw at 2 out. The YZ carbs come with a #7 slide, which is ideal for the 38mm carbs.
Here's what the YZ carb looks like.
So by sealing up the power jet, you're not running any of the carb electronics?
I believe a guy on TT was running the YZ carb on his 05 cr250 and had the electronics wired up
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