Posts
53
Joined
8/2/2024
Location
Cordova, TN, USA
Okay guys so here are my findings...
I was noticing a bog when revving the bike and after revisiting the carb I noticed the choke knob was still up 🙈 So hopefully that's all that it was, but I wanted you guys to review my jetting and tell me if you thought it could use some tweaking. Again, I'm running at 93 ethanol free, 32:1 Klotz super techniplate, and about 400' above sea level riding motocross. This is a Keihin PWK Airstriker on a 2002 CR250.
Main Jet 165
Pilot jet 52
Needle is on the bottom most clip position
Air screw approximately 1 turn out...
These settings seem wrong from what I remember and the pilot jet also looks a little clogged. What do you guys think?
The choke and clogged pilot are not helping your cuase. mains usually end up around 170-175 and your needle clip position should be closer to middle to start with, last clip on bottom is very rich… also depends on what your needle is…I have an airstryker on a 96 hpp engine that is jetted to perfection but the engine also is built by TmR. Hopefully Digger can chime in and offer guidance with the 02 engine jetting.
Ironic you mentioned digger because after some digging I found one of his recommendations in another thread that I think I'm going to go with.
New jetting will likely be:
This yamaha needle https://www.partzilla.com/product/yamaha/4SR-14916-EJ-00?ref=68faf61d93b0a2ff37d4e2aec733077f5ac1d686 on the 3rd clip position
175 main
48 pilot
and open the air screw up to at least 1.5 turns and go from there.
I think the guy had the needle bottomed out to compensate for how lean the main was at 165. Looking at how he did other things on this bike I'm not surprised the jetting was a little off.
Digger I hope you stumble upon this. Going to order the needle and jets tomorrow unless I get some strong suggestions otherwise.
Which exact model PWK? Shorty/flat top or long body/screw top?
What number slide is in the carb?
What fuel, oil and ratio are you running?
The 52 pilot is rich, I'm running a 42 and 45 pilots and 170 and 175 mains on 2 last gen Cr250's.
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It's the screw top knockoff Keihin 38mm airstriker. No markings on the slide. 93 ethanol free, kltoz super techniplate 32:1
It actually ran seeminly okay the last time I took it through the gears down the street but definitely could stand to get better. I had spooge all over the swingarm last time I started it and warmed it up but again that was probably due to the choke still being on LOL
Good to hear. I think I may start with the 48 and 175 and at least get me in the ball park.
Sounds like you are running rich. Unlikely going up on the main will help that.
Well I still have the 165 to play with, but the thing is when it was bogging and spooging my choke was up the whole time lol
As you go down on the pilot it will take fuel from the whole range so you may have to add some on top when you get it right. Your needle is full rich as well.
We need more info, we need to know exactly what needle you're using. Everything gets jetted around the needle.
What needle do you like using on the last gen? I have a 01 rm pwk with tps I’ve been meaning to try on my 04 cr again
On your 04', I would use an NEDW in the # 3 clip, 172 main, 42 pilot. Those 01' RM250's, I believe came with a #7 slide, so you should be good there. Don't forget to block off the power jet.
JD Jettings blue and red needles.
I’ll have to check and see what the stock needle is. I tried it with jetting close to that but it was too fat and it was too hot out to mess with it any more so I put the mikuni back on haha
Digger,
This is the needle I ordered to mess with:
https://www.partzilla.com/product/yamaha/4SR-14916-EJ-00
As far as what is in there right now I am not sure. Will have to check again tomorrow when I get to the garage.
That N3EJ in clip #3, 48, 178, should work pretty well. It should have a nice little hit into the mid, when used with a #7 slide. It might be a little lean though, when the weather gets a little cooler.
N3EJ is a good needle which yields very good throttle response and is a personal favorite. However it is slightly lean in the middle, but not a show stopper. 50/50 with your ethanol free pump and C12 or Sunoco Supreme leaded helps significantly. Be sure to have the squish clearance corrected on your head. Stock clearance is large.
Can you post a pic of your carb?
Pit Row
Sure will. I will get some uploaded later this evening.
The guy I bought it from said he "orders the carbs off ebay and puts Keihin parts in them" but after meeting him and breaking the bike down I'm not sure I believe that the carb components are genuine keihin.
Here's the old knock off Keihin. Apparently I can only do one pic at a time. The jetting/needle comes in today. May keep this stock needle until I get it more dialed.
I would like to see the venturi.
Is that the air box side?
So I went with the 48 pilot and left the 165 main in there along with the stock needle it already had but moved the clip position up to 3 instead of 5. I just need to set the air screw 1.5 out instead of 1 turn and go from there I reckon.
If that "stock" needle came with the carb, it is a random spec, not specific to the bike.
FYI, that slide cutaway height from the bottom should be 9mm, if it's a #7. If it is say 8mm, you can diy it to 9mm. Just sayin'
That is good info. I just finished the total restoration of this bike yesterday. I'll measure it once I get it back off the bike.
Before
After
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