Attn: 2002/2003 CR250 Keihin PWK Converts

[maninuniform66100]

I think you all who are having problems,maybe have other problems i am running the same and 76 on on 2 clip ,s8 370 my bike has it going on big time no problems...try mr 2 race gas will make the mixture leaner and advance your sator 1 mm from the mark....mike in ca at 3000 ft and 90

 

[James]

James,

I've been running the '01 Cr motor in a '02 chassis since '02. I love the setup, JMS Performance has done all the motor work (they did the Factory Connection team's 125 motors since '00). It has strong power from bottom up, definately does not have the hesitation/abrupt transition from low to mid as the new style motors.
Basically built new head stays, ran '01 radiators (for routing reasons), built new swingarm/cases spacers, and not too much else.

Good luck and have fun.

I had put all of the original engines back in their original frames after rebuilding the 00 and 01 this winter and didn't have the heart to yank the 02 apart, so the whole experiment is on hold (I would like to ride more than I mechanic this year).

Did the front motor mount on the down tube match up? I don't think it would be much problem to get new head stays made but I don't know anybody that I would trust with a welder on my frames. Also, I am curious about mounting the silencer?

Thanks

 

[Borch297]

The front motor mounts just need to be enlarged. Get some CR 125 head stays, someone to match the bend (as the 250) and downsize the overall length.

 

[691RACING]

Faded,
Im running the pwk on my 02 cr 250 which i purchased thru fuel technologies, i switched the main from 175 to 182,slow jet 55 and clip 2nd from top and could not ask for a smoother power delivery. List of mods include eric gorr low end porting, boyesen rad valve, boyesen exhaust flange, fmf sst pipe and silencer.

Best of all no spooge..

 

[Faded]

691,

Thanks, I have my carb now I just need time to install/test it. What needle are you running and at what altitude? Mine came with the stock 2000 CR250 needle, still trying to figure out if this will work or if I should order something else...

 

[pace]

As my top-end has worn in a little, and as I've started riding the bike more aggressively (previously was on a 125), and as the weather has changed, I've found that my jetting has gotten VERY finicky. It really doesn't run cleanly at partial-throttle high-rpms, and I find myself using the throttle like a light-switch. I'm thinking I'm going to move straight to the Keihin and skip all the $$ outlay on needles and slides and so forth that many of you have gone through.

The price on the Keihin makes it very attractive, but being at high-elevation (5,500-6,000ft) I'd like to establish some kind of baseline jetting that will get me in the right ballpark. Is there anyone else here that rides over 4,000ft who has made the switch? I'd be grateful if you would share your jetting specs.

With the Mikuni, I've at least had the owners manual to get me in the ballpark. Does anyone know if the jetting chart from the MY2000 CR250 owner's manual is available online any place?

TIA.
-Pace

 

[bedell99]

Hey andrew give us some updates with that Keihn of yours.

Erik

 

[Faded]

Hey andrew give us some updates with that Keihn of yours.

Erik

Erik,

Sorry to say, but still no time. :debil: I'm in the process of reparing/selling/closing on my current home, packing/moving and building a new house myself, all while holding down two jobs... :bang: I've put 4 hrs on my bike since May. Sorry, but it might be a while before I get around to it.

 

[parkerCR]

The PWK works well on my 01 CR250. I rarely need to fool with anything but the main jet. It is definitely better than the Mikuni in my opinion. I have grenaded my CR twice in the past 18 months and not sure why. Though, the carb has nothing to do with that. I would recommend the PWK to help resolve the jetting battle one engages in with the Mikuni.

 

[pace]

Would anyone be willing to scan the jetting chart from the '00 owners manual for me? Assuming it has one, of course..

I can purchase the owners manual from the HRCA website, but it seems a waste of $16 just to snag a look at a single page.

-Pace

 

[pace]

Installed the PWK on my '03 this morning. It's a pretty straightforward swap. No significant clearance issues, although I did remove one of the overflow tube guide/retainers since it was a little closer to the shock spring than I'd like. I'd say this carb qualifies as a 'direct swap'. Nothing has to be hacked or replaced to make it fit. The stock '03 throttle cable is a little longer than would be ideal, but I was able to take up all the slack with the knurled adjuster.

Since I wasn't able to get hold of the jetting chart from the MY00 owners manual, I made educated guesses on initial jetting based upon the input of others. All my riding is between 5,500ft and 6,000ft above sea-level. The carb came installed with the 2000 CR250 specs, including a #180 main and #48 pilot. 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'm on the stock #7 slide and stock A715/289R/A327/A487 needle.

My house is situated at an elevation of 8,600ft so I was expecting the bike to be running way rich. It actually started first kick on the choke, and I was able to take it off the choke immediately. After a 5 minute warmup, I took it for a brief squirt. It's a little fat at WOT, but elsewhere felt surprisingly crisp. I obviously won't play with the jetting until I get it down to track elevation.

I'll reserve final judgement until I have the carb properly setup at the track, but my initial impressions are very positive. The bike immediately feels snappier coming onto the powerband than it ever has on the Mikuni, and this at 3,000ft higher elevation. Exhaust gases look cleaner too.

If anyone is interested in seeing the carb in situ, I can take a couple photos to show clearance, etc.

-Pace

p.s I premix Amsoil series 2000 synthetic at 36:1 with our (crappy) oxygenated 91 octane pump gas.

 

[CR Swade]

Faded, how do you like that 265 kit? Worth the money? Its too hot to ride here in the summer so I was thinking of going that way along with porting. Suggestions?
P.S.
My Keihin still works great on my bike, even after the switch to Ultimate 2 and some minor jetting tweaks.

Just got back from a day in the woods and track w/ my 265. All I can say is DAMN! Whatever specs Eric ported this thing to, it flat out hauls. Literally leaps from turn to turn and each gear is very long. Nothing out there today could keep that bike in sight today, even the big 525 that runs w/ us. The Mikuni is a bit confused down low, but I got that helped out w/ the pilot and needle clip. Other than that is starts easy and has excellent response. This bike easily outruns my 01, which I loved and feels about 5-7hp more than any 250 I've ever ridden. I'd be curious to see what Eric's dyno results are showing on the 265's. The only other mods are SST pipe and V-Force...this beotch hauls

 

[pace]

Since I wasn't able to get hold of the jetting chart from the MY00 owners manual, I made educated guesses on initial jetting based upon the input of others. All my riding is between 5,500ft and 6,000ft above sea-level. The carb came installed with the 2000 CR250 specs, including a #180 main and #48 pilot. 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'm on the stock #7 slide and stock A715/289R/A327/A487 needle.

Just wanted to follow up on this. The PWK has made a massive improvement in throttle response, jetting consistency, and in combination with a PC shorty silencer the CR has picked up a nice helping of midrange hit. Low end power characteristics are unchanged, but instead of pulling linearly into the midrange the bike now explodes into the powerband with a more traditional 250 feel.

As for the jetting. My guestimate specs seem pretty darn close. Either that or this carb is just extremely tolerant of suboptimal jetting specs. The one thing I have noticed is that the bike surges slightly when decelerating after closing the throttle. In particular there is one big table I clear (after a fast section) with a slight downhill after landing. Trailing the brakes into the downhill and I can feel the motor fighting me to keep momentum. The idle adjustment is not the issue since the bike just barely idles without stalling. Am I running a little lean on the slow circuit? Incorrect float height, maybe?

Best $150 I spent. Once I get used to the increased throttle response I may have EG work his magic too.

-pace

 

[bedell99]

Thank you pace for the review, one question though did you notice more consistenc with the jetting. Taking from 5000ft to 8000ft.

Erik

 

[Faded]

Pace,

I've some how been inspired by your findings and have decided to make the swap sometime this week and take it to the track on Saturday. I opted to order the R1368NS needle (from the '98-'01 CR500, same as the pre-alum. framed CR250s) and give that a try. My best guess for my bike @ 4700ft will be;

Float Level = 16mm
#42 Pilot
Stock #7 Slide
R1368 Needle, 2nd Clip
168 Main

I'll be going tomorrow as well, still toting the Mikuni. Going Saturday with the Keihin will be as close to back-to-back as I get, but it should still give me a pretty good idea. We'll see how she does. . .

 

[pace]

If you're on pump gas then if I were you I'd start with no leaner than a 172 main. I'm at 1,000ft higher elevation and my bike feels good with the 172. I could maybe go one step leaner. You should need a richer main than me. A 168 main would be 5 steps leaner than stock, which is a pretty big jump right off the bat. As I said though, the PWK seems to tolerate inexact jetting much better than the TMX.

Erik - I have not really run the bike at extremely high elevations except for a brief shake-down at my house (8,600ft) when I first fitted the carb. It started and ran just fine (a little bit fat maybe). I mostly ride at Watkins or Lakewood and have not had to change the original jets I fitted for moving between those tracks nor for changing weather. The carb's 'tolerance' for changes in ambient density is massively improved.

One thing I noticed is if I don't warm the bike fully, but pull away from the pits and abruptly snap the throttle to half-open, the bike bogs briefly. Once it's warmed up and on the track, it never does this. Based on the comments others have made on the stock needle, it might be a tad lean I guess.

-pace

 

[Faded]

If you're on pump gas then if I were you I'd start with no leaner than a 172 main. I'm at 1,000ft higher elevation and my bike feels good with the 172. I could maybe go one step leaner. You should need a richer main than me. A 168 main would be 5 steps leaner than stock, which is a pretty big jump right off the bat. As I said though, the PWK seems to tolerate inexact jetting much better than the TMX.

02 CR250 + 15ccs + Mo Betta Porting = Leaner Than U. :cool: Also, I have a few of my buddy's bikes to reference; a '97 CR250 and '99 CR250 that run 168's and a Mo Betta '98 CR250 that has a 165. All use the R13xx series needles and run strong in the warm months without problems. The air here is dry as a bone as well.

Not positive, but I also think the stock '00 needle (A715/289R...) has a larger straight section than the R1368NS I'll be using. Not 100% sure, but by looking at the designators I'd venture a guess that the '00 needle is 2.715mm dia. while the R1368NS is 2.685mm, which would have an effect on main jet size (among other things).

 

[pace]

Sorry.. didn't catch the 265. Yeah, I went to leaner jetting when Eric built my YZ144. Colorado air is also very dry btw - it helps improve the otherwise low ambient air density at these elevations.

Let me know how it works out for you. You might not realize quite the same benefits as me since Eric has already sorted your motor, but I think you'll be pleased with the consistency of carburation at the very least.

-pace

 

[Faded]

Bump to the top, any new members to the PWK Club?

 

[mtk]

Not yet, but seeing as how I just bought a CR500 engine for my 2000 CR, it looks like I've got a 38mm Keihin PWK that needs a new home. My 2002 CR250 might be just the place. :)

 

[D36-108A]

After fiddling with the 2002 CR250 Mikuni to no good effect, I took the Keihin PWK take-off from my 1995 KTM (!), jetted it like my 1997 CR250, and never looked back. More consistent and smoother. I made the swap in the spring when I lived in California. I just rode it at Moonrocks (5000 feet) yesterday and it ran great, even at trolling speeds riding with my beginner brother.

The tab on the top of the PWK doesn't have a notch to fit into in the intake boot, but it fits close enough.

 

[pace]

Bump to the top, any new members to the PWK Club?

TTT.

Did you make the swap to the PWK? What were your impressions?

-pace

 

[CR Swade]

I just bought one, haven't installed it yet, was in getting my knee operated on, but I will be installing it this next week. If it starts cleanly, maintains a constant idle point and sounds crisp, that will be a start.

 

[soulmate33]

Bump to the top, any new members to the PWK Club?

I did mine about a month ago. Just plain awesome.........

Out temps here in Honolulu, Hawaii is about 80 degrees F with about 70-80 percent humidity. I'm at sea level.

Due to the occasional ping, I run VP C-12 at a 50/50 mix with Chevron premium unleaded with AMSOIL racing oil @ 50:1. If I'm feeling wealthy that weekend, I'll run the C-12 straight without having to do any jetting changes. Just sweeter smelling exhaust smoke easier on the nose.

I got a 38mm PWK Air Striker with 2000 CR250 jetting.
#7 slide, 48 pilot (2.25-2.5 turns out depending on humidity), 180 main, and middle clip position A715/289R/A327/A487 needle.

She bolted right up without problems. Just had to take up the slack in the throttle cable slightly. My BR8EG plug is reading ever so slightly on the richer side. I'd rather run it this way to be on the safer side. No fouled plugs yet after 5 rides.

The slight miss at 1/4 throttle is gone now. It has definite smoother roll on power. I have a Vforce Delta 3 reed cage and use a 49T sprocket.

I have an FMF Power Core silencer with any 1 of the 3 FMF pipes depending where I'm riding. I run an E-line pipe guard at all times. Fortunately the one guard fits all 3 pipes.

• Fatty: Great throttle response that quickly explodes into the power band. Lotsa low and midrange power with some over rev lost on top.
  
• Gnarly: Same as Above. I use this one definitely for trail riding. I should have bought this pipe first being that I have no use for the FATTY now.
  
• SST: I use this one for the MX track. Revs don't come as quick as the pipes above. Definite increased over rev with slightly less low end power. Lotsa mid and top end.
  This pipe seems to keep the torque within a broader RPM range without the instant off idle hit.On the MX track, I switch gears less with this pipe as opposed to the FATTY or GNARLY.

Gonna be selling my Mikuni TMX on that popular auction site soon..............

My 2 cents..... :cool:

Tracy

 

[Faded]

TTT.

Did you make the swap to the PWK? What were your impressions?

Pace,

I did make the swap. Unfortunately I have only ridden with it for a short period and really didn't get to dial it in or play with it, so I can't really give any solid impressions yet. It'll be a while before I get to ride again too, the weather here in Idaho is less than desirable for riding. I will say that I was impressed by how smooth it was even with ballpark jetting. Sorry I don't have more to add, but I am looking forward to next year.