Pro Circuit porting and head mods for 02-04 CR250's review

[ace402]

So I took my Pro Circuit modified CR250 out for the first time today. All I can say is WOW!! It is easily the fastest bike I have EVER ridden. These bike are way underrated.

For a little background I've ridden a 1999, 2002, and 2003 CR250's with PC pipes and the the 02 and 03 had Vforce reeds. All those bikes had decent power with the 99 having the best overall engine. The 99 had more bottom with a little less midrange and about the same top maybe a little more than the 02 and 03's.

When I would ride the 02 and 03 back to back with my old 2005 YZ450F I could tell that even though the 250's hit harder, my 450 was definitely faster. I'd bet $20 that if I could get traction that I could beat my old 450 on my new 250. Like I said, i've never ridden a faster bike.

I'm not sure what Pro Circuit did to the head and cylinder but what ever it was it turned the bike into a rocket. It's weird, but it's like they were able to shorten up the bottom end power if that makes any sense. It doesn't have a ton of snap right off bottom but it picks up into a monster midrange sooner than the other CR250's i've ridden. For instance, say you would have to wait until 1/3 throttle for a stockish CR250 to wake up, this engine would wake up sooner say around a 1/4 throttle. Or maybe it would be 1/8 throttle instead of 1/4. So pretty much if you're anywhere except right off idle the bike has a ton of power. Either way, I hope you get the point. The midrange is beefed up and it definitely revs out further than stock as well. I don't need any more power than what this bike has. In fact, sometimes, I wished it didn't have as much power as it does.

It's definitely not a lazy mans bike and if your technique is off the engine is much less forgiving than a four stroke. It demands that you be in shape and use proper technique. I ended up swapping out on a slightly whooped out straight away that was really slick. It ended my day but I had a TON of fun. Makes me wish I had sold the 450 sooner. Once I get used to the power and stop trying to ride it like a four stroke I think I'll be turning faster lap times.

I'm going to call Pro Circuit tomorrow to see if they can look up their records and tell me what exactly they did to the cylinder and head. They're not the cheapest tuners out there, but this is a COMPLETELY different engine and bike for that matter compared to the other CR250's i've ridden.

My bike:

2002 CR250

PC pipe and shorty silencer

Boyesen Rad Valve

PC cylinder and head mods

VP U2 mixed at 44:1 with Amsoil dominator

[onefasthonda]

Nice review. Do you know how much hp you added?

[ace402]

No, I bought it this way. I will say though that it definately seemed faster than my old 450 and that had 48.1 HP from the factory I think.

[4 STROKER]

PC claims 52rwh with their port and head. Its fast!!! I rode A PC 02 and that is what convinced me to buy a 02 cr. My 250/265 runs noticeably stronger than the PC 250 but I hear PC will build you a 265 and that is what I would have done if I did not do my own motor work. I have seen pc port/head work and I pretty much copied it but added to it some to boost the top a little more. If you have good throttle control it is easier to ride than a stocker because of its much wider power band. If you play gun and run with it on a MX track you better know what you are doing because its will hurt ya way faster than a stocker will. Only down side CR's that make big HP drink nothing but race/av gas.

[erik_94COBRA]

Be sure to post back if you find out what they did to your cylinder. Have you tried running pump gas? Or do you know for sure that you need to run race gas?

[CamP]

A buddy of mine has a full mod '05 and it runs neck and neck with my stock '08 CRF450. It is a avgas or race gas only engine. One experiment with pump gas ended with a stuck piston.

[ace402]

I called PC and their records don't go back that far. They said that the next time I do a top end I could send them the cylinder and head and they'll tell me what they did. They say they cut the head for either race gas or pump gas. I'm not sure which mine is cut for. I've only run race gas and that's all I'm going to run. The previous owner said I could run either but I kinda think he said that so I would be more inclined to buy the bike. The PO only ran race gas. If it is set for race gas the guy I spoke to at PC recommended VP C12. He said that the engine needs at least 108 octane. I'm going to try and send the top end in sometime this winter.

[ace402]

PC claims 52rwh with their port and head. Its fast!!! I rode A PC 02 and that is what convinced me to buy a 02 cr. My 250/265 runs noticeably stronger than the PC 250 but I hear PC will build you a 265 and that is what I would have done if I did not do my own motor work. I have seen pc port/head work and I pretty much copied it but added to it some to boost the top a little more. If you have good throttle control it is easier to ride than a stocker because of its much wider power band. If you play gun and run with it on a MX track you better know what you are doing because its will hurt ya way faster than a stocker will. Only down side CR's that make big HP drink nothing but race/av gas.

Where did you hear that they are around 52 HP? I wouldn't doubt it but the guy at PC I talked to today didn't have any experience with that engine so he didn't know what it would put out.

You're absolutely right that the power is wider but that you must also be careful lest you get yourself in big trouble in a hurry. PC said that they will cut head for pump gas if the customer asks them. Mine is going to see no less that VP110 and maybe C12 if I can afford it. I thought I read somewhere that these CR250's are prone to pinging even when not heavily modified. Is that true?

[ulmanb]

I thought I read somewhere that these CR250's are prone to pinging even when not heavily modified. Is that true?

Mine seems to be prone to pinging. Usually if I richen the jetting slightly it seems to help. Seems to pin a little more after I had Eric Gorr do some cylinder porting to it.

[4 STROKER]

"Where did you hear that they are around 52 HP?" In I think it was Dirt Rider there was a small artical on a pro circuit kit for the new 02 cr250 that put out 52rwh it was port/head work pipe silencer. The mag said it was alot faster than stock but power was still smooth.

[APBT]

Mine seems to be prone to pinging.

The pinging is frequently caused by excessive squish clearance. The '05-'07 seems to be worse than the '02-'04 with the squish issue.

Edited September 18, 2010 by APBT

[ulmanb]

good to know, may be something I deal with this winter then.

[MotoGuido]

Thanks for the review!!

Although... now I don't think I'm gonna have any work done to mine lol. It's already a handful with v-force reeds and procircuit exhaust haha.

So I think I spend the money on suspension first! Maybe just more compression on the rebuild (were at 5kft here) and leave the rest alone.

[PowerFiend]

good to know, may be something I deal with this winter then.

Check out this guy for the head mods:

www.rb-designs.com

[busted bones]

Mine seems to be prone to pinging. Usually if I richen the jetting slightly it seems to help. Seems to pin a little more after I had Eric Gorr do some cylinder porting to it.

2 strokes are much more susceptible to pinging than 4 strokes for quite a few reasons, thats also why they tend to require much higher octane gas even though the compression in a 4 stroke is much higher. You can do 14.5:1 in a 250F and still get away with 91.

[cottonmoutham]

love the cr 250 i also have one modded by pro circuit the most fun and fastest bike i have ever ridden mine is a 06 cr 250r

[APBT]

My 250/265 runs noticeably stronger than the PC 250 but I hear PC will build you a 265 and that is what I would have done if I did not do my own motor work.

Does the 265 overbore need to be bored off-center? Is there enough cylinder wall thickness on the exhaust side to allow on-center boring?

[4 STROKER]

I have been getting them bored on-center. No problems yet.