Jetting ??? need a bit o help

A reference for the PWK carbs...
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FLAKDX
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Jetting ??? need a bit o help

Post by FLAKDX »

I just put a fresh top end in my 220 and cleaned up all the carbon and spooge from the power valves. I heat cycled the motor twice now and took it for a short spin around my neighbor hood. The bike seems to have developed a bit of an off idle bog. Almost feel like a lean bog type feeling. No amount of tweaking the air screw or idle has had any effect. I spent a good bit of time getting the jetting spot on before I did the top end it was damn near perfect.

I ended up with a 142 main 40 pilot and close to 2 full turns out on the air screw. This was perfect before to the point of snap throttle wheelies with no clutch in 1st thru 3rd. Now I'm getting a hell of a stumble when I twist it open anything short of very slowy.

Opinions before I start tearing the carb apart? My gut instinct is I need to go back up to a 42 pilot. Do you think I could get away with simply going up a notch or 2 on the needle?? I didn't open the air crew past 2 1/2 turns should I try going further with that?
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m0rie
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Post by m0rie »

I'd start with putting the 42 pilot back in and reset the airscrew to 1.5 turns out. Stock needle? If so go ahead and put it on the 4th clip and see what happens.
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Post by FLAKDX »

Thanks Morie. thats was my feeling to T :partyman:
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Post by Colorado Mike »

142 Main? at sea level? seems lean to me and I'm riding at 9000'. but maybe our bikes are way different. My profile is pretty accurate if you want to compare setups. Keep in mind that the jets interact a little, sometimes the main can have more of an effect down low than you would think. If it's a lean bog, and you move the clip up a notch or two on the needle, you'll make it worse. If it's lean, you turn the air screw in, not out.

Also, you say you just put a fresh top end in and then you had the problem. Are you absatively posilute that you put the right size piston in? I had a bike that needed an oversize piston in it, the doofus mechanic put a stock one in. It would start, idle, rev fine in neutral, and didn't sound bad. try to rev it under a load, and it would stumble and take forever to clear out . I put the right parts in and solved that.

good luck,
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Post by Indawoods »

Mike... there is no mention of your jetting in your bike profile.
There is a jetting primer in this forum if you want to diagnose the problem. I just put it up last night.
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Post by skipro3 »

Check your needle clip position and be sure the needle is seated right. I had a lean bog like that; crawling along, crack the throttle and the bike almost would die. Then the rpms caught up and off I'd go. Set the clip one richer and it was beautiful. Besides, it's simple to check that needle. Could be something got caught in the needle jet oriface too. You may need to just flush the carb out good.

As a cheater method, grab a rubber mallot and wack the carb a few times while riding down the road. I've had some success dislodging gunk that way.
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Post by FLAKDX »

Mike the cylinder measured out well within spec even the stock piston didn't look worn. This bike had very little time on it before me. I only changed it because of the suspect weak stock pistons in the 220.

I went ahead and changed the pilot back out to 42 and cleaned the carb really good. My needle was in the 4th position but ever since I broke an e-clip in my shifter kart I always check it whenever I have the carb open and everything looked clean but I blasted every orifice with carb cleaner anyway just to be sure.

Didn't get a chance to test it after the Jet change last night as it was pouring rain again :roll: in sunny south Florida. I'm gonna go out this afternoon and do a few plug chops and mess with it some more. Gonna start fresh with new synthetic pre-mix and a handfull of plugs till I get it right again.

I sure hope that it's not the piston as Mike described :shock:

Only other thing thats coming to mind is I have a Boysen Rad Valve. While I haed the cylinder off I took the Rad Valve out to check reed tension. One corner on the bottom side of the reeds was just slightly lifted. I went ahead and fliped both reeds to get them back perfectly flat. Old Trick I've used in the past :? Do any of yall think that could have anything to do with it????
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Post by skipro3 »

oh, hey!!!

Did you put the piston in the right direction? If it's 180 degrees out, it will run but the intake port timing will be weird. The top of the piston should have an arrow on it pointing to the exhaust. Pulling the head will reveal, but you might be able to just pull the pipe and use a bright light and mirror to check for the arrow.
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Post by FLAKDX »

LOL Yeah the arrow is forward. I had heart failure for a split second when I started reading your post till I thought it through :shock: I was very carefull to make sure I put it back in the right direction. :rolleyes:
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Post by jack10525 »

Any luck figuring this out? I having a similar problem too but I have a 200 and just did a near complete rebuild. Splitting and all. I have a low end bog but the thing flys in the upper end. I'm just south of you in Homestead FL. My jetting is way different than yours too which I am gonna play with soon. I'm running stock 1174 needle, 162 main, 48 pilot and I have the air screw turned out about 1 1/4 turns. It starts on the first kick and idles good but there is that low end bog. From the difference between mine and yours I'd say you're running a tad lean. I'm sure I'm running prettty rich. Good luck dude.....
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Post by Indawoods »

Man jack that a BIG main! I have a 200 too and I am running a 150! You need to come down to at least a 155 and your pilot to a 45.... Then you'll start getting close...
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Post by KDXGarage »

A 200 has a 35mm carb, and the 220 has a 33m carb, besides very different porting, so that might explain some carb jetting spec differences.
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Post by FLAKDX »

It was just a simple matter for me anyway of going back to the 42 pilot. It RIPS now. No hesitation, no Bog just snappy power. I'm really happy about how crisp the bike is now with a fresh top end. :supz: :supz:

Rode yesterday at the MX track for a few hours. Finally getting the courage up again to jump :shock: did most of doubles and all but the one monster table top. Still can't get the nerves up to jump over 40 feet :oops: Pretty impressed with how well the ol KDX handled the track. A few clicks on the compression and it wasn't bad. At least I though it wasn't bad till a dude let me ride his 04 RM 125. Now THATS suspension :prayer:
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Post by 89kdx200rdr »

flak if you thought your pilot was lean shouldnt you have tried going in with the airscrew? maybe try 1 turn out with the 40?
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Post by jafo »

>|<>QBB<[quote="FLAKDX"]It was just a simple matter for me anyway of going back to the 42 pilot. It RIPS now. No hesitation, no Bog just snappy power. I'm really happy about how crisp the bike is now with a fresh top end. :supz: :supz:

You got me wanting to tear down my bike and re-ring it now. I can't remember my pilot jet size but the main jets are the same between our bikes. I think we have the same exact jetting. Kicks a$$ does'nt it!? real snappy. Watch out in the colder weather though. I think that main jet is about to the limit before leaning out. I found in the colder weather that it's alittle harder to start. I have'nt found this out for sure, but it's my best guess. Bike starts easy after it's warmed up. could be alittle of both, jetting and ring wear. Just wanted to let you know in case it happens to you.

Jon.
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