I have the PC Works pipe and fmf turbinecore 2. I only ride trails and the abrupt powerband can be a little much in the woods sometimes. I was wondering if anyone had tried the gnarly on their 2005-2007 cr250's that could tell me how it worked for them?

I doubt the Gnarly would make enough of a difference for the money spent on it.

Most people do a flywheel-weight and rear sprocket to tame these machines a little bit.
These bikes were made for motocross, so they have that sudden hit of power.
I know mine doesn't like to be lugged around.  It has lightswitch power.  Some people like it, some people don't.

I always liked it.

Best thing for you to do is
Mill .025" off the base of the cylinder
mill head the rest of the way to set squish up to .045"  Stock squish is .084"   this is to big, and leads to detention.  
Mill combustion chamber to set compression ratio per fuel you are going to use.
Buy a pwk 38 air stricker carb for the 2000 cr250.  $187 from powersports plus

This is how my motor is setup.  I did all the work myself.  Best 250 motor I have every ridden.  Great low end torque, smoother mid. and some loss on top.  But you have a pc pipe witch is a top end pipe.  I am running the Gnarly.  So you will have more top end then I do.

 SandMantis, on 23 July 2012 - 04:59 PM, said:

I am sitll a two stroke newbie so dont take this the wrong way as I might be completely wrong, but doesnt the size and shape play a huge role in the power charactaristics of a 2t motor? As I understand it, the size and shape of the pipe dictates the speed/timing of the exhaust pulses returning to close off the exhaust port. If the pipe is tuned (shaped) to take a long time for the pulses to return to the port, It would be more efficient at low rmp's and if the pules return quickly it is better in high rmp's. I know this is all probably standard knowledge for most on here but if this is true then one could only assume that the pipe would play a huge role in the making good low or high end power. I understand that other things such as case volume, port angles, compression, and squish all come into play also. I guess I was just under the assumption that a pipe would make a big change.

Edited by kneedrag05, 24 July 2012 - 09:21 AM.

Fwiw the gnarly worked well for my 03 at the noticeable expense of top end.  I stall less in turns, and pull through them with less clutch work. It won't turn your cr into a rm with strong power right off the bottom,but you'll notice a difference. Still had to dop 2 teeth in back. I don't miss the top end, less climbing the tank on jumps now.

 Kirkes, on 23 July 2012 - 06:40 PM, said:

You can also use the short body PWK from a late model RM or YZ which fit better than the long body PWK on the '04-'07 CR250

I don't know what every body is talking about.  the long pwk fit great on my 05 cr 250.

Does the flywheel weight make a big difference? Have any of you guys tried it?

Don't waste your time with the pipe or flywheel weight.  The carb is worth the money.  And having the cylinder and head modified will be well worth the money.

From Eric Gorr's site (exactly what Kirkes described):

Quote

http://www.eric-gorr...t2-Strokes.html

 Kirkes, on 24 July 2012 - 03:22 PM, said:

Ditto.

I have the same one, and it fit good on my `05 CR250R.

 kneedrag05, on 24 July 2012 - 04:21 AM, said:

Well, you are correct with your info here, but we were referring to the differences between a PC Works pipe and a Gnarly pipe.
It is true, you can get a 2t engine to perform differently by tuning it with the pipe, but most of these aftermarket pipes are pretty close to each other.
There is not a big enough difference to produce drastic engine performance differences.  That's all I was saying.
The differences would be a slight change in the powerband at different RPM ranges.  If it's important to you to maximize your powerband in the range you are looking for,
then you might want to spend money for a specific pipe.  I know people who changed pipes and it made no noticeable difference that they could actually "feel".
The differences might show up on a dyno, but oftentimes we "perceive" a change because we spent money on something and "want" it to make a difference.
Most of the time, we just move the power peak around the RPM range, so it "feels" different because it hits in different spots.
Some like a quick hit, other people like a long top-end runout.  Actual "peak HP" can be the same.  It just feels different in different RPM ranges.

Kirkes is correct also.  These engines can benefit from a cylinder base mill and head job.  CamP did the same thing to his engine, and it makes a difference.
I didn't do it to mine, because I am pretty happy with mine the way it is, so I just left it alone.
Next time I have to do a top-end, I will probably do the cylinder base mill on it.
I run race gas, so I don't worry about detonation.

if anyone is wanting a flywheel weight but doesnt wanna spend the money then i have got one i would sell.. for a 03 cr250. i bought it used on ebay for 60 bucks. i would sell for 40. i never installed it on my bike. i decided i like it how it is

 Kirkes, on 23 July 2012 - 06:40 PM, said:

i just did all the same stuff and did my first ride with jetting i made a total guess on. my current jettingis 45 pilot, 175 main, (forget needle jet at the moment) 1 turn out on the AS. ktm 250sx short body pwk.

 Kirkes, on 23 July 2012 - 06:40 PM, said:

did you have to run race gas after milling the cylinder and head? how would the setup be if only milling the cylinder?

No race gas.   I milled my combustion chamber bigger so I did not have to.    
But real gas is getting harder and harder to find.   I will the switch to 100LL and bump my comp. up to make better use of that fuel.

 shootz, on 21 February 2013 - 08:02 AM, said:

I have an 07 with only the cylinder base milled .030". It requires 100 octane fuel, minimum. If you want to run pump gas, you need to add 3cc of volume to the head's dome.

Edited by CamP, 21 February 2013 - 04:51 PM.

 Kirkes, on 23 July 2012 - 06:40 PM, said:

Have same carb for sale now for $40 less. Price above doesn't include shipping but mine does.