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Discussion Starter #1
Hey guys, heres the problem, if anyone can help I would greatly appreciate it.

02 600 XCSP bone stock except dial-a-jet. 380 mains, 40 pilot (stock) The sled runs great everywhere in the rpm range except when I am just barely moving (slow vehicle speed and about 5,000 RPM) and I crack the throttle. It bogs for a split second(or rather just cuts out) and sometimes backfires(through the exhaust). I adjusted the pilot air screw through it's entire travel with no noticeable difference in the bog/backfire except when the needle was all the way in(rich) it got real bad. I figured pilot circuit first cause it's a low end thing. All I can think is maybe I need to go down 1 pilot size. Any thoughts or advice or anything would be great. Thanks.
 

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id just say go down one full main jet size. you are just getting to much fuel if the want to with the pilot fine but id say this wont help much
 

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Discussion Starter #3
If that was the case don't you think it would show on my plugs and affect the performance in other areas also? It's only at very low speeds and rpm's. How much does the main circuit have an influence on the low end? My plugs look perfect.
 

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Is it warm out when this occurs? Or when the sled hasn't warmed up? Does it get better when it's really cold out? I agree with timespent - could be a rich bog. What does your jet chart say?
 

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Discussion Starter #5
It's about 10-20 degrees and it does it all the time as far as engine temp. I have dial-a-jets on it and I'm 5 jet sizes down from stock.
 

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Possible something is wrong with dial a jets? Have you tried regular jets to verify?
 

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I have a 2001 XC 700SP that is doing the same thing. I tried to adj. fuel screws too and it did nothing. It is to lean. Try giving it half choke and it will not bog. I am going to take apart carbs and blow out jets and see if that dose it.
 

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02 600XCSP just wondering when you crack it are you talking about pinning it. Because the jetting circuits are based on throttle position, ie full throttle is main jet. That is where everyone got the drop the main a size theory.
 

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I'm going take a different angle, and say you are lean. I do not have any dial a jet experience, but I think I understand their operation. 380 is pretty lean for a 600, and after you're at 1/2 throttle and above the dial a jet may compensate extra fuel OK, but at small throttle openings I'm thinking the dial a jet does not react fast enough, so you are having a lean situation, especially with the backfire. Try some 400 or 410 mains, and back down the dial a jet a little, and see what happens. I'd like to see you jet for 25-30 degrees F, and then turn up the dial a jet for cold temps.
 

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Discussion Starter #12
Thanks for the mass input and sorry I didn't get back to all of you sooner. The throttle cable is adjusted properly. It has about 1/8 inch play. Turning the choke on makes it a whole lot worse. I talked to the Dial a jet guy and I'm definenately not to lean overall. I'm actually one main size up from what he said he runs. I do mean pinning it when I say cracking the throttle.

SnoFast, "after you're at 1/2 throttle and above the dial a jet may compensate extra fuel OK,but at small throttle openings I'm thinking the dial a jet does not react fast enough, so you are having a lean situation, especially with the backfire. " Technically it starts compensating at any engine load but it really "works" (flows a lot) at higher throttle openings. It does flow at all times as long as there is any load.I've already been at 400's and worked my way down. I always though a backfire through exhaust is rich and backfire through carbs is lean, but I know that from 4 strokes(vehicles). Does that not apply with 2 strokes? I agree it is a lean condition(or rich) but overall the sled runs great and the plugs look beautiful. I don't want to lower my overall performance cause I have a small bog at low speeds, I think I just need to figure out how to tweak the transition stage between pilot and main operation, but there are so many possibilites as far as the main circuit. Needle jet, jet needle, throttle valve, main jets, etc. You guys have given me a lot of food for though and I really appreciate it. Keep it coming if you think of anything more. :D
 

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Discussion Starter #13
I think next I'm going to go down 1 more main size, I'm just nervous cause that is really a small jet to me. :unsure:

Also, I can pin it from a dead stop and it takes off like a bat outta hell with no bog or pause but bogs when I crack it and I'm already moving slow.
 

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Discussion Starter #14
Just thought I'd let you guys know I lowered the e-clip 2 spots (richer) and it solved the problem. The thing runs insanely good now. Thanks for all your input.


I strongly recommend dial-a-jets!!! :D
 
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