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01 CR250 jetting w/ new PWK carb

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So I just bought an 01 CR250 with the stock Mikuni carb. I just ordered a PWK (from a 2000) from Service Honda. My question is- Is the stock jetting (that these came w/ in 2000) as rich as they were stock in 01? I ride at sea level in 70-80degree temps (mostly out in Ocotillo Wells). I'm wondering if I should mess with the jetting on this new carb or leave it...  My bike before this was a 99 CR250 and I never touched the jets! I honestly don't even know what they were at, it was good so I never messed with it. Hoping to have the same luck with this one.

 

Thanks for any input.... BTW, I read through TONS of threads on this swap on this site and others. Definately a wealth of info on here!

 

-Chris

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You are going to get a lot of different opinions on this.. So, I'll just close my mouth & post what I'm running on my '01 CR250

 

Keihin PWK 38MM Air-Striker

Pilot: 42

Main: 175

Needle: 2nd clip (may move it to 3rd clip as weather cools)

Vforce3 Reeds

FMF Gnarly Pipe

FMF Shorty silencer

 

I will say this.. I started with the factory 48 pilot and it was way too rich. I then dropped to a 45 pilot and it ran better, but still splooged quite a bit out the exhaust and felt like it would load up idling when the engine was hot. Finally dropped down to the 42 pilot and the bike is super crisp from idle all the way to WFO. Has a small hesitation at about 1/2 throttle which I am attributing to the needle being on the 2nd clip. When I had the 45 pilot in it did not have the hesitation. I'm at sea level but temps are 90-100 most summer days. We are still in the high 80's even at this time of the year.

Edited by Kawabuggy
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Start with the stock '00 jetting, and adjust as required for your setup, location and riding.

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The carb is going to come setup pretty close, but most likely a little rich. Most people seem to end up with a 45 pilot on pump fuel in the summer and a 48 in the winter or when running race fuel. The needle may be anywhere from 2nd to 4th clip but seeing as your at sea level you will probably have it at the 3rd or 4th clip. Depending on how much wide open riding you do most people report running a 175 main. The fact is that no matter what anyone else is running with a similar bike in similar conditions every bike is going to be different. In the summer at 80-90 degrees and roughly 500-1000 feet I was running a 45 pilot, cej needle (which is either the same or very close to your needle) in the 3rd clip and a 175 main. Now that the temps are down between 45-65 degrees I am running the 45 pilot (for right now) 4th clip, and 175 main. The pilot is borderline and I will probably swap a 48 in there this week and test that out. Haven't had a chance to do a plug chop yet to see if the 175 main is still going to work and to tell you the truth I haven't had the bike over 1/2 throttle since the temps dropped either. Jetting is very seldom a set it and forget it thing, but the keihin is much more forgiving than the mikuni. If you get it dialed in at 80 degrees you will probably be ok from 70-90 degrees at sea level. It's not going to be perfect at 70 or 90 but it shouldn't be so far out that your risking a seizure or fouling plugs.

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Thanks for the info guys. For my first ride I think I'll leave it stock and see how it feels (and bring an extra plug LOL). I'm going on a desert trip like literally right after this carb is supposed to arrive. Kawabuggy- I have the same exact reeds and exhaust on mine so maybe later I'll try your settings. I'm a total newbie to jetting, I've read the articles on how to figure out exactly what your bike needs but I don't really have the time or patience to go through all that- nor would my neighbors appreciate it! So I'll copy what has worked for others and see how it does...at least as a starting point. Thanks again

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Note that the type of needle you run has a big effect on the pilot and main sizing. Your OEM '00 needle will jet differently that an aftermarket single taper needle like the CEJ, so be wary of of jetting recommendations unless they are running the same needle that you have. Elevation, temp, humidity, fuel and riding type also have a big influence, so be very careful when leaning it out, or risk sticking a piston.

 

Also note that most people juggle mains and pilots, when in fact the needle has the most influence on the way the bike runs.

Edited by CamP
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You are going to get a lot of different opinions on this.. So, I'll just close my mouth & post what I'm running on my '01 CR250

 

Keihin PWK 38MM Air-Striker

Pilot: 42

Main: 175

Needle: 2nd clip (may move it to 3rd clip as weather cools)

Vforce3 Reeds

FMF Gnarly Pipe

FMF Shorty silencer

 

I will say this.. I started with the factory 48 pilot and it was way too rich. I then dropped to a 45 pilot and it ran better, but still splooged quite a bit out the exhaust and felt like it would load up idling when the engine was hot. Finally dropped down to the 42 pilot and the bike is super crisp from idle all the way to WFO. Has a small hesitation at about 1/2 throttle which I am attributing to the needle being on the 2nd clip. When I had the 45 pilot in it did not have the hesitation. I'm at sea level but temps are 90-100 most summer days. We are still in the high 80's even at this time of the year.

kawabuggy's got a good suggestion. this right here will get you going nicely @ ocotillo.

Edited by mynewcr250

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Note that the type of needle you run has a big effect on the pilot and main sizing. Your OEM '00 needle will jet differently that an aftermarket single taper needle like the CEJ, so be wary of of jetting recommendations unless they are running the same needle that you have. Elevation, temp, humidity, fuel and riding type also have a big influence, so be very careful when leaning it out, or risk sticking a piston.

 

Also note that most people juggle mains and pilots, when in fact the needle has the most influence on the way the bike runs.

Good advice.  It's better to start rich with the stock jetting of the carb & work towards leaner than vice a versa..

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Figured I'd report back after my first desert trip with this bike. WOW, this thing is tits! I'm comparing it to my old bike which was a 99 CR250. That thing was a total dog on the bottom end. I loved that bike but it was kinda weak. This bike w/ this carb has tons of power throughout and it handles better to boot. I was even surprised at how on some hill climbs i didn't have to be completely in the powerband the whole time. Absolute blast to ride. I'll be riding this bike for a looong time. Anyway, as far as the jetting on the Service Honda PWK carb on got- I left it factory except I moved the needle clip to the second position. Some mentioned the factory set jets were way too rich. I dunno, from how it ran it seemed perfect. This was riding sea level out in the desert (Ocotillo Wells) with temps in the high 90's.  I didn't get a lot of spoodge out the exhaust but I also just put fresh packing in the silencer so that could be soaking it up...? I should look at the plug. I did bring an extra on my trip expecting it might get fouled but like I said it ran perfect the whole time. Love it, couldn't be happier!

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