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KX265 input needed

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As some may remember my friend shattered a piston skirt here recently. So, he sent it in to Millennium for a 265cc big bore and their more everywhere porting. Everything is ready to go for start up except the pipe. He has been running the stock '03 pipe but also has a PC works pipe he could use. Which pipe would be better for a more wide power range with maybe a bias towards bottom-mid power? He went with the 265 kit hoping to pick up a little more bottom end so he could maybe go back to stock gearing (currently 13/50) or even higher to get some more top end speed.

Also, bike has stock carb and was running 162 main, 48 pilot, and 50 power jet on the the standard bore. Bike is ridden almost every weekend and raced in hare scrambles from 2000' to 6500' above sea level. Only mods to the bike are the aforementioned big bore, Vforce III reeds, and FMF turbine core silencer. This always seemed way rich to me and was thinking about dropping it to a 155 main and maybe a 45 pilot and start doing plug chops. Does this seem like a good starting point or am I way off?

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Thanks for the suggestion but my buddy isn't looking to spend any more big bucks for a while as our race season is coming up. He currently owns the two pipes I asked about so it's the cheap way for now.

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The stock 03 pipe is actually quite good overall.  That is what I ran on my 03 with a 99 motor.  The issue with the 2003 250 was more of a problem with the porting and power valve design.  That same pipe with different porting revs out on top pretty well and still retains strong low-mid.  I did not like the Pro Circuit pipe on that motor.  It is all top end.  No bottom end and the midrange is even fairly soft.  It wants to run on top but in stock form the rest of the 03 motor can't keep up.  I tried a spacer in the head pipe which did move the power down into a usable range but it also caused detonation under high RPM, low to mid throttle conditions.

The stock 03 pipe spreads the power out very well and doesn't try to hit too hard anywhere. 

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I think they run out good with the stock pipe .my personal Kx runs awesome with a PC/q stealth weird combo but the bottom is there and I've tried 3 different pipes . I like the power spread on a fatty too but Everytime I use one I dent it in a few rides .

Sent from my Moto G (4) using ThumperTalk mobile app

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7 hours ago, turbo dan said:

The stock 03 pipe is actually quite good overall.  That is what I ran on my 03 with a 99 motor.  The issue with the 2003 250 was more of a problem with the porting and power valve design.  That same pipe with different porting revs out on top pretty well and still retains strong low-mid.  I did not like the Pro Circuit pipe on that motor.  It is all top end.  No bottom end and the midrange is even fairly soft.  It wants to run on top but in stock form the rest of the 03 motor can't keep up.  I tried a spacer in the head pipe which did move the power down into a usable range but it also caused detonation under high RPM, low to mid throttle conditions.

The stock 03 pipe spreads the power out very well and doesn't try to hit too hard anywhere. 

This is 100% accurate. My first KX was a 03 and it had the PC Platinum pipe on it (same as Works just silver finish). Bike had very little low or low/mid range power. Had an 04 KX250 later on with the stock pipe and it was SO SO much better than the 03 for low and low/mid range power. I'm sure the 03 could come around but not with that PC pipe on it. 

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Back years ago when I made mine a 310 I used the PC pipe that was on my bike when I got it but I also had the stock 99 pipe in the shop. I put the motor together and it ran ok (good), I then leaned it out a fair amount, don't remember what I ended up on but it is still close to that, I do know I bounce between a 40 and a 42 pilot jet though. Anyway I went out one day and thought I would try the stock pipe too. I started the ride with the PC like it had been since I put it together and then about half way through the day I put the stock pipe on and it ran fine with the PC on but the stock pipe just ran SO MUCH better it was not even funny. I ran the stock pipe for years after that. I now bounce between stock and a Noleen that this cylinder like too, but the stock one is awesome on my bike. I'm getting older now and not riding quite as much as I use to but 2 weekends ago I went up to Idaho and rode the Sawtooth's and my bike rocked as it always does and made my riding look good LMAO.

 

Ed

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Ok, trying to get the jetting sorted on this thing and I'm at a loss. The needle has no markings whatsoever. Ugh. Ran it last weekend with a 162m, 48 pilot, a/s way out, needle in 2nd from top. It was smoking bad, gurgling, and lifeless. Just swapped out for a 155m, 42 pilot, a/s 2.5 turns out, needle (???) middle clip. Bike smokes much less and throttle response is much improved. Air screw says still too rich but figuring it will probably be ok when our temps are in the 50's and 60's. I have done no plug chops at this point as I want to get a needle in there that I know what it is.

So, I need an idea for a needle so I can start sorting this out. Would a CEK needle be a good place to start? Please, I really need some input on this one!

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I hear of good results with some suzuki needles (necw I think?)  I run a JD needle in mineand have had good results.  the stock needles are generally way to rich, esp being in arizona.

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Current needles I have on hand are BGL, BGN, CGJ, DGJ, and an R1368H that doesn't seem to cross over to the three letter code. Would any of these work for a decent starting point?

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7 hours ago, SS109 said:

Ok, trying to get the jetting sorted on this thing and I'm at a loss. The needle has no markings whatsoever. Ugh. Ran it last weekend with a 162m, 48 pilot, a/s way out, needle in 2nd from top. It was smoking bad, gurgling, and lifeless. Just swapped out for a 155m, 42 pilot, a/s 2.5 turns out, needle (???) middle clip. Bike smokes much less and throttle response is much improved. Air screw says still too rich but figuring it will probably be ok when our temps are in the 50's and 60's. I have done no plug chops at this point as I want to get a needle in there that I know what it is.

So, I need an idea for a needle so I can start sorting this out. Would a CEK needle be a good place to start? Please, I really need some input on this one!

Suzuki needles work well

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