Selecting a Pipe for an 02 CR250

SmogNazi · May 2, 2005

Hey guys-

I'm trying to decide on a pipe for the 02 cr250 i just bought. It is bone stock for now. I plan on not touching the engine other than airfilter, pipe, and reeds. I do more trail riding than anything, will occasionally take it to the track and desert but mostly looking for low to mid torque. I'd like to stick with FMF, I like the tight sealing o rings.

Should I go with a fatty or gnarly expansion chamber?

I need something with a spark arrestor so I don't get a ticket in CaLiberalfornia so I'm looking at the TurbineCore 2 and the Q pipe. How much loader than stock is the turbine core2? I don't want to be repacking all the time, i assume the Q needs to be repacked more...Anyways, thanks for helping me out!

Erik

CR Swade · May 2, 2005

you need to budget in for a carb also, a 38mm PWK...the stock Mikuni is a turd. I used a FMF SST w/ a Turbine Core on mine

tyesai · May 2, 2005

I have an 04 CR250R and put the Gnarly pipe on their with shorty power core II, I love it. If you are going to be doing alot of trail riding I would also get a fly wheel weight, I have a 12 ounce from Steahly and think that that is the best mod I have done so far to the bike, it smoothed out the power some what but made the bike almost stall proof, you can really lug it around down low. Good luck.

SmogNazi · May 2, 2005

tyesai-

Did you upgrade to a PWK 38mm carb or just jet the stock one?

Erik

mtk · May 2, 2005

SmogNazi said:
Hey guys-

I'm trying to decide on a pipe for the 02 cr250 i just bought. It is bone stock for now. I plan on not touching the engine other than airfilter, pipe, and reeds. I do more trail riding than anything, will occasionally take it to the track and desert but mostly looking for low to mid torque. I'd like to stick with FMF, I like the tight sealing o rings.

You do know that on a 2002, the O-ring is on the exhaust spigot and there is no functional difference between a stock, FMF, and ProCircuit pipe in the sealing department.

I've read that the stock Mikuni can be dialed in using a James Dean jetting kit (www.jdjetting.com) but I've never done it myself as I put a 38mm PWK on my 2002 CR250.

I also had the cylinder ported by Eric Gorr, to "Mo Betta" specs. I don't have the jetting fully dialed in yet, but so far it has filled in the bottom end nicely and gave it a nice boost all around. The 10oz Steahly flywheel weight also helped with traction and stalling on trails.

Before I spent money on a new pipe, I'd get a flywheel weight and consider sending out the top end for port work. The only down side to porting is the time it takes to send it in, get the work done, and get it back.

SmogNazi · May 2, 2005

Hey- I was going to look into porting. I don;t want to go that route until the motor needs a rebuilt which should be this coming winter...I don't mind getting a new pipe since the bracket on the stock one is broke. I found a pretty sweet deal anyways. I cannot decide between the procircuit platinum 2 and the fmf gnarly. I though the FMF was the only pipe with an o ring? Mine is spitting a little premix from that area so maybe the stock pipe is in need on an oring. Thanks for the info. I'm also gonna get a flywheel weight, how hard is the install on that and what size do you recommend. I weight 250lbs and will go mostly trailriding, and mostly crusing around the track, nothing too hard.

Erik

mtk · May 3, 2005

I have a FMF Gnarley, FMF Fatty, ProCircuit Platinum, and a stocker. All of them are identical in how they mount to the engine, i.e. there IS NO O-RING on the pipe end, period. If it is leaking, remove it, clean it, and put some high-temp RTV in the pipe end before you reinstall it. That will solve the leaking problem. You could replace the spigot O-ring at the same time, for good measure, but the RTV is the big one.

As for pipes, the Gnarley is a low-end pipe. It will boost the low end at the expense of the top end. The ProCircuit is more of an all-around pipe (I don't own a Platinum 2 so I can't coment on it).

As for flywheel weights, they are simple to install and take maybe 20 minutes, tops. On a 2002, the 8 and 10oz Steahly weights require no cover spacers; the larger weights do. Given that, I prefer the smaller ones (one less gasket is one less spot to leak). I'd go with a 10oz, which is what I did myself. I'd also suggest you pull the five aluminum clutch plates out of the clutch pack and replace them witth five steel plates (the stock clutch uses five aluminum and two steel plates). That will give the bike a bit more rotational inertia and act kind of like a flywheel weight. It is not nearly as pronounced, but it is a noticable change. It will also keep the aluminum clutch plates from fouling the tranny oil so badly and so quickly.

The biggest fix for the low-end is the port job. Anything else is a compromise.

I'd also sugest a 38mm PWK. Lots of folks have been VERY happy with that swap.

soulmate33 · May 3, 2005

I'm glad to hear you bought the bike!

As for the pipes, I have:

Stocker - Best all around power
FMF Fatty - low to mid gains, lose a lot of top over rev
FMF Gnarley - same as above
FMF SST - mid to top gains with lotsa over rev, bottom end is lost though. This one is good for the MX track, less shifting.
Pro Circuit Works - Good all around but not as good as the stocker.

After buying and trying all of the aftermarket pipes, I've come to realize the best way to get power gains every where is with Mo Better porting from Eric Gorr. With all of the money spent on pipes, I could have had a big bore 265cc kit with a port job already! Which by the way is gonna happen in the next 2 weeks hopefully.

I did swap my carb to a Keihin 38mm PWK with V-force 3 reeds.

I say buy the cheapest pipe you can (save your money for the port job, I wish I did), go up 2-3 teeth on the rear sprocket (I run 49T on the track and 51T in the trails), change your clutch plates to all steel.

You can only buy pipes made for a 2002 CR250. 2003-2005 will not fit. Check the auction site epay,I found some awesome deals on pipes (my recent one was a brand new Pro Circuit works pipe for only $110, I bought 2 new FMF Fattys for $120 each).

Have fun..............

Tracy

mliebal · May 3, 2005

Interesting, I did put on a 2003 Gnarly w/o problem. I am using the stock silencer. I have just gotten a shorty to try, but have not installed.
I made too many changes and have not ridden much in order to comment on the performance. But as for fit the 2003 gnarly did fit.

Good luck to you.
Mike
2002 CR250
mo-beta, Keihen carb, rad valve, torque spacer ( note:may make a difference in the fitment of pipes?)

James · May 3, 2005

I am pretty sure 2002-2004 are interchangable as far as fit goes. 2005 does have a different pipe setup.

Mike, I didn't know that they had swindled you into a Keihin carb also? When did you do that?

mliebal · May 3, 2005

Hi James,
Looking for that perfect woods bike. The mo-betta and gnarly pipe opened the jetting req's box. Between age and traveling I can not remember the details, but I needed some other parts for my Mikuni, and for the price difference just went with a new carb. I am still working on the jetting (do we ever complete this task?).

Some day, I am going to put on the stock pipe for comparison.

Mike

James · May 3, 2005

mliebal said:
Hi James,
Looking for that perfect woods bike. The mo-betta and gnarly pipe opened the jetting req's box. Between age and traveling I can not remember the details, but I needed some other parts for my Mikuni, and for the price difference just went with a new carb. I am still working on the jetting (do we ever complete this task?).

I tried the Keihin thing and it isn't bolt on perfect either. At some point, you should be mostly done jetting but I have to change the main jet and adjust the air screw all the time, Keihin or Mikuni.

My Mikuni was running SO GOOD on Sunday, 3rd gear felt like 2nd. It was too good actually and I raised the needle one clip to try and soften it a bit and it ran like crap afterwards. I think the Mikuni works really well when its right and I haven't found any special magic in the Keihin swap yet. Maybe I'll try it again this summer.

soulmate33 · May 3, 2005

My bad....James and mliebal are right about the '03-'04 pipes being able to bolt up. I called FMF and Pro Circuit on this.

They said the reason for the 2002 pipes having its own part # is because the '02 engine is different from the '03-'04 and by swapping the pipes optimum performance would not be obtained.

pace · May 3, 2005

James said:
I tried the Keihin thing and it isn't bolt on perfect either. At some point, you should be mostly done jetting but I have to change the main jet and adjust the air screw all the time, Keihin or Mikuni.

My Mikuni was running SO GOOD on Sunday, 3rd gear felt like 2nd. It was too good actually and I raised the needle one clip to try and soften it a bit and it ran like crap afterwards. I think the Mikuni works really well when its right and I haven't found any special magic in the Keihin swap yet. Maybe I'll try it again this summer.

Odd. My PWK was 100% bolt-up perfect.

IMHO the difference between the PWK and Mikuni is not so much that one makes more power than the other when they are both setup correctly. Rather, the Mikuni is good when it's good, but it's extremely finicky the rest of the time. The PWK seems more tolerant of changing ambient conditions or imperfect jetting. At least it does on my machine.

When I was on the Mikuni, I was changing jets every ride. I've done a season on the PWK now, and have only changed the jets twice in that time - one of those occasions was this past weekend when I took the bike down to Moab which is at significantly lower elevation.

James · May 3, 2005

Are you are running the PWK with the 48/180 needle in the center? Elevation?

I am not necessarily saying anybody is wrong, I just haven't had any spectacular results by switching.

I have ridden a 2000 CR250 for 3.5 years with the Keihin carb and easily have to change jets more than twice a year if I want it to run great every time. That is generally for temps alone because I rarely ride outside of 600-1500 elevation. Actually, I often have to change jets in the Keihin due to the difference between morning/afternoon/evening temps.

I can see how the Keihin might be a bit more tolerant of temperature changes in the low to mid range because of the slide design, but I don't see how that would eliminate messing with the main jet and even the pilot/needle for major seasonal changes especially since I know I have to do it on the 2000, which has better low mid power in the first place.

The Keihin may be marginally better, but I can get my 01 and 02 to run very strong with the S-8 nozzle and some jets. The stock S-9 runs great when it is cooler. So all of that combined makes me a little skeptical of this Keihin kick that everybody is on.

CR Swade · May 3, 2005

on my 01 I got the Mikuni to run hard, run clean and hardly had to touch the carb, it never needed a Keihin. My 02 was a total nightmare...sometimes it would be close, but never perfect. The other times it was just plain laughable as to how far out of whack it would get from just a weather change. The Keihin solved all of that on my 02

there are lots of ways to get that 02 running down low, the Keihin is an easy start

pace · May 3, 2005

James,

My PWK came with the 2000 CR specs - #180 main and #48 pilot w/ A715/289R/A327/A487 needle. I changed this to a #172 main (-3 sizes) and a #42 pilot (-2 sizes). I moved the needle clip up one position from the middle to the second position. I set the air screw to 2.5 turns out. I retained the stock slide and stock needle. These settings worked great in the Colorado summer temps (~70-90 deg) last year, but I had the bike ported this past winter, and while it ran fine in the cooler temps with these jetting specs it's now a little fat on top since the weather has warmed up. I will probably drop the main to a #170.

My riding is mostly at 5,500-6,000ft ASL.

I never believed the Keihin to be a fix-all for the '02-'04 CR. However, I did find it to be an important piece of the puzzle that when combined with some other careful modifications, can help transform the bike from sleeper to fire breather.

James · May 4, 2005

Thanks for the info Pace.

To clarify my "bolt on perfect" comment, I was responding to Mike's "I am still jetting - does it ever end" comment, since he (like you and I) may have to change the jets from the factory settings. In that respect, it doesn't just go in and run perfect.

Like I mentioned earlier. I will try it again this summer and see if I notice an improvement this time. I have parted the 00 so I figure I need to do something with that carb.

mliebal · May 4, 2005

Great information guys.
I had my 2002 with the Mikuni for over a year w/o needing to change the jetting for seasonal changes. It would have helped some for woods, but not too bad. Once I had the porting and pipe, I really needed a lot of jetting help. And even when it was close, the performance was real sensitive to temp/elev changes.
I was hoping for a majic bolt on solution (silly me). But no.
The Keihin seems more stable.
I am running way lean. #7 slide and 38 (or is it 37.5) pilot and the air screw still needs to be out 3.5 turns. The top end feels incredible. I have a more lean slide to try, still.
The bike now feels like a mx bike (explosive), which is not ideal for the woods (or my spode style).

pace · May 4, 2005

James said:
Thanks for the info Pace.

To clarify my "bolt on perfect" comment, I was responding to Mike's "I am still jetting - does it ever end" comment, since he (like you and I) may have to change the jets from the factory settings. In that respect, it doesn't just go in and run perfect.

..went back and re-read your comments, and I get what you were saying now. I had misunderstood and thought you were alluding to fitment issues. My bad. :nod:

James · May 4, 2005

pace said:
I had misunderstood and thought you were alluding to fitment issues. My bad. :nod:

My communication skills tend to be lacking...probably my bad. :cool:

mliebal · May 4, 2005

James,
"Probably" what do you mean by that?

Just curious.

James · May 4, 2005

mliebal said:
James,
"Probably" what do you mean by that?

Just curious.

LOL - troublemaker.

Hey, go to the other message board and tell me when you are going to be able to ride before/after WV. I need to ride your 'new' bike.

Selecting a Pipe for an 02 CR250

SmogNazi

CR Swade

tyesai

SmogNazi

mtk

SmogNazi

mtk

soulmate33

mliebal

James

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