04 CR 250 jetting

adamwedge
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adamwedge
What's everybody close to sea level running in the Mikuni? I have a 390 main and 27.5 pilot and it makes power then falls on its ass. I seek the crispness.
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erik_94COBRA
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erik_94COBRA 9/27/2016 3:52am
9/27/2016 3:52am
adamwedge wrote:
What's everybody close to sea level running in the Mikuni? I have a 390 main and 27.5 pilot and it makes power then falls on its...
What's everybody close to sea level running in the Mikuni? I have a 390 main and 27.5 pilot and it makes power then falls on its ass. I seek the crispness.
I have an '05 CR250 and am running similar jetting in the Houston area. 380 MJ, 27.5 PJ, 3rd clip, AS ~1.5. Runs pretty good overall. I have had my cylinder lowered by 0.030" and the squish adjusted accordingly.

Any other mods on your bike?
adamwedge
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adamwedge 9/27/2016 6:18am
9/27/2016 6:18am
Fatty and shorty exhaust. Fresh plug and fresh air filter.

I also notice 1st gear never cleans up, but will get on the pipe 2nd-5th.
adamwedge
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adamwedge 9/27/2016 4:59pm
9/27/2016 4:59pm
I went with a 400 main and 32.5 pilot. Air screw at 1.5 turns out, really runs like shit now. Any suggestions?
macz400
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macz400 9/27/2016 6:20pm
9/27/2016 6:20pm
that main and pilot are what I run but also run a JD needle. Do you have any problems with gas leaking out of the overflow tube of the carb?

The Shop

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adamwedge
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adamwedge 9/27/2016 7:19pm
9/27/2016 7:19pm
macz400 wrote:
that main and pilot are what I run but also run a JD needle. Do you have any problems with gas leaking out of the overflow...
that main and pilot are what I run but also run a JD needle. Do you have any problems with gas leaking out of the overflow tube of the carb?
No sir not a drop. I had everything apart and cleaned before I swapped jets. It idles beautifully but when getting on it there's lots of blubbering now.
Randy_Nix
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Randy_Nix 9/27/2016 7:55pm
9/27/2016 7:55pm
i have an 02 cr250, same carb, i used to be able to jet a 4 stroke carb pretty well but not the mikuni. im curious to see what everybody is running.
adamwedge
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adamwedge 9/27/2016 8:17pm
9/27/2016 8:17pm
Me too! I know this thing can run better than it is!
captmoto
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captmoto 9/27/2016 9:05pm
9/27/2016 9:05pm
Keihin AS carb from a late model YZ. Jetting problems go away.
macz400
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macz400 9/27/2016 10:31pm
9/27/2016 10:31pm
buy an 04-07 JD jet kit for $75. Bike will run excellent. I've had tons of CR250's and Ive had that kit on damn near every one of em. The Keihin carb swap is also a good alturnative.
adamwedge
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adamwedge 9/27/2016 10:33pm
9/27/2016 10:33pm Edited Date/Time 9/27/2016 11:58pm
Say I swapped to a Keihin, what happens with the wiring for the RC valve? I didn't see any with the sensor?
adamwedge
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adamwedge 9/27/2016 10:34pm
9/27/2016 10:34pm
macz400 wrote:
buy an 04-07 JD jet kit for $75. Bike will run excellent. I've had tons of CR250's and Ive had that kit on damn near every...
buy an 04-07 JD jet kit for $75. Bike will run excellent. I've had tons of CR250's and Ive had that kit on damn near every one of em. The Keihin carb swap is also a good alturnative.
What did you end up running from JD? Runs pretty good you say?
809
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809 9/28/2016 5:13am
9/28/2016 5:13am
adamwedge wrote:
Say I swapped to a Keihin, what happens with the wiring for the RC valve? I didn't see any with the sensor?
You can wire the tps up on the keihin also
adamwedge
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adamwedge 9/28/2016 5:27am
9/28/2016 5:27am
Is there a specific model of the Keihin that has a spot for the sensor?
adamwedge
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adamwedge 9/28/2016 5:36am
9/28/2016 5:36am
Some are saying you can get a non TPS equipped pwk and bike will run fine?
arvid
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arvid 9/28/2016 8:45am
9/28/2016 8:45am
I run without the TPS no problem. try get a short body Keihin it fits much better .
captmoto
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captmoto 9/28/2016 11:31am
9/28/2016 11:31am
adamwedge wrote:
Say I swapped to a Keihin, what happens with the wiring for the RC valve? I didn't see any with the sensor?
There is a guy on Thumpertalk that sells a conversion harness but your bike runs fine without it. CamP on thumpertalk has messed with CR carbs extensively and there is a shitpot full of info on the Keihen swap.
I did mine and it is super simple and no more jetting headaches.
People were changing out the s8 nozzle to an s7 and there is supposed to be an o-ring that leaks causing the rich problem down low. It still doesn't fix the fickle jetting issues completely though.
adamwedge
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adamwedge 9/28/2016 12:27pm
9/28/2016 12:27pm Edited Date/Time 9/28/2016 12:31pm
Thanks for all the replies. It was actually rideable with the 390/27.5. I put in 400/32.5 and it just blubbers, won't even get on the pipe.

No crazy excess smoke so I don't think it's too rich, I've probably put two hours on it on a new br8es as well. I did notice that I have a small chip in the corner of the reeds but I can't see daylight....shouldn't cause this, right?

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adamwedge
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adamwedge 9/28/2016 12:32pm
9/28/2016 12:32pm
captmoto wrote:
There is a guy on Thumpertalk that sells a conversion harness but your bike runs fine without it. CamP on thumpertalk has messed with CR carbs...
There is a guy on Thumpertalk that sells a conversion harness but your bike runs fine without it. CamP on thumpertalk has messed with CR carbs extensively and there is a shitpot full of info on the Keihen swap.
I did mine and it is super simple and no more jetting headaches.
People were changing out the s8 nozzle to an s7 and there is supposed to be an o-ring that leaks causing the rich problem down low. It still doesn't fix the fickle jetting issues completely though.
What carb did you end up running Capt?
adamwedge
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adamwedge 9/28/2016 1:21pm
9/28/2016 1:21pm Edited Date/Time 9/28/2016 1:21pm
Thoughts? This is looking into the boot that mates with the reeds, after a 3 minute ride

CamP
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CamP 9/28/2016 7:34pm
9/28/2016 7:34pm
adamwedge wrote:
Is there a specific model of the Keihin that has a spot for the sensor?
Any late model YZ, RM, KX short body carb with TPS will work. I run YZ carbs on my CR's and I hook up the TPS to take advantage of the 3D ignition mapping.

When running the TPS/powerjet carb, you need to replace the powerjet with a threaded stainless steel plug from a hardware store.
adamwedge
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adamwedge 9/28/2016 11:11pm
9/28/2016 11:11pm Edited Date/Time 9/29/2016 12:40am
I do have my Kehin PJ on my 125 I could try out...any reason I shouldn't? And what would do with jets? 125 has a 168/55. Been working with 400/32.5 on the 250. Throw those in?
captmoto
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captmoto 9/29/2016 3:14pm
9/29/2016 3:14pm
adamwedge wrote:
What carb did you end up running Capt?
Keihin from a late model YZ250. 175 Main, CEJ needle on 3rd clip and a 42 main jet.(I think)
Randy_Nix
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Randy_Nix 9/29/2016 6:03pm
9/29/2016 6:03pm
im at 1200 ft. elevation. i had a 420 main jet with a 27.5 pilot 2nd clip on the needle and 1.5 out on the air screw. i just changed to a 390 main jet on the 3rd clip on the needle and its waaayy crisper and pulls way harder. it honestly surprised me. the 420 MJ was way too rich
JW381
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JW381 9/29/2016 6:30pm
9/29/2016 6:30pm
Randy_Nix wrote:
im at 1200 ft. elevation. i had a 420 main jet with a 27.5 pilot 2nd clip on the needle and 1.5 out on the air...
im at 1200 ft. elevation. i had a 420 main jet with a 27.5 pilot 2nd clip on the needle and 1.5 out on the air screw. i just changed to a 390 main jet on the 3rd clip on the needle and its waaayy crisper and pulls way harder. it honestly surprised me. the 420 MJ was way too rich
Why did you richen the needle? I'm running a 400MJ right now, 2nd clip, cant recall the pilot at the moment, air screw is about 1.75 turns, works well. The Temps are changing so we'll see. I had port work done by gorr, fresh rings, reeds, clean power valve, thinner base gasket. So it's not the stock setup, but not exactly mod either. I'm anywhere from sea level to 1500'.
adamwedge
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adamwedge 9/29/2016 7:00pm
9/29/2016 7:00pm
Well I did a leak down test today and it sat solid at 8 psi. I'm going to order reeds and hopefully that helps.

I did notice today on the Mikuni that it's on the 3rd clip. If I'm understanding correctly, it will lean out some if I move it to the second?
Dan-The-Man
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Dan-The-Man 9/29/2016 7:37pm
9/29/2016 7:37pm
So many different jetting recommendations without knowing the mixture you're using and the mixture they are using. It is a piece to the puzzle.
Dan-The-Man
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Dan-The-Man 9/30/2016 6:47am
9/30/2016 6:47am
I have an 04. I'm running a PWK though. I would check the reeds, mine were already chipped on the corners at low hours. Also check the powervalve cables. The powervalve servo will only pull so far and if the cables are loose the powervalve doesnt open all the way.

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