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klx250s help please rejet

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I bought a low miles 09 klx250s. I did the kdx snorkle, modded stock muffler to open up, K@N filter and a jet kit. I used the 127.5 jet as i was told from sigma. The bike doesn't seem as snappy as it was before the carb rejet and i have a hessitation at 4k rpm. What could it be? I didnt drill the slide and put one shim under the needle.

thanks for any help

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I ride a klx300 with the stock carb which probably is close to the same vacuum slide arrangement as on your bike. Jetting a carbed bike like yours involves dealing with 3 fuel circuits.

 

1. Idle circuit. The idle screw influences fuel at idle and just as you come off idle. Set the screw at 2 turns out from closed and leave it alone for now.

 

2. Needle circuit. The needle controls fuel flow from off idle to about 3/4 full throttle. 

 

3. Main jet. The main jet has the most control at full throttle.

 

4. They all three flow fuel when the bike is running.

 

Knowing that what I would do is pull the plug and look at the insulator. If it is dark in color it is running too rich. If light in color or white it is running too lean. What you want is a nice light tan insulator.

 

Your hesitation at 4000 rpm suggests to me a posible lean condition in the lower half of the throttle which would mean raising the needle a bit.

 

One you get your needle and main jet sorted out you can mess with the idle screw if you need too. There are a number of ways that people use to set the idle mix. Thumper Talk has a How Too in their maintenance section.

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argh, i appreciate the help. I wasn't looking forward to  pulling the thing apart again. Is if possible to do it without removing the carb this time?

thanks

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I do not have to remove the carb to make jet changes. I take the tank off to adjust the needle and remove the float bowl to make main jet changes. Depending on how much stuff you have hanging around the carb you may have to loosen the front and rear clamps that hold the carb in place to roll it outward in order to better expose the bowl. I also have developed a special set of tools that make the process easier. I am at the point where it is just work and not much of a challenge to accomplish the task. Once again I am working with a 300.

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I bought a low miles 09 klx250s. I did the kdx snorkle, modded stock muffler to open up, K@N filter and a jet kit. I used the 127.5 jet as i was told from sigma. The bike doesn't seem as snappy as it was before the carb rejet and i have a hessitation at 4k rpm. What could it be? I didnt drill the slide and put one shim under the needle.

thanks for any help

 

Who's jet kit?  Did it come with a new needle, and if so, where did you place the clip?

What's your elevation?

On your exhaust mod, I've seen elsewhere where riders have tried to open up the klx250 stock exhaust but it seems that the results are mostly increased noise without much if any increase in flow & performance.  Not sure what you've done, but just keep that in mind as it may be nearly as restricted as before.

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Who's jet kit?  Did it come with a new needle, and if so, where did you place the clip?

What's your elevation?

On your exhaust mod, I've seen elsewhere where riders have tried to open up the klx250 stock exhaust but it seems that the results are mostly increased noise without much if any increase in flow & performance.  Not sure what you've done, but just keep that in mind as it may be nearly as restricted as before.

Hind sight is definitely 20/20. I ordered the Sigma kit on Epay, should have ordered the DJ. No it didnt come with a needle and i am at 2k feet. SHould i look into a slip on muffler and ditch my modified muffler? I put one shim under the eclip, i know it needs at least 2 and i didnt drill the slide.

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The DJ needle is far more aggressive than the stock needle and IMO is the primary value of a DJ kit.  Some guys get the 49-state N1TC (I think that's it) adjustable Kaw needle as a replacement.  Some reports I've read suggest shimming the stock needle provides only limited (if any) improvement.  If you're trying to get the most power, think about a slip on.  There are a number of decent setups out there.  I picked up a slightly used HMF off ebay and it made a significant difference, but it's raspy and loud.  Now have an FMF Q4 setup with powerbomb which I like much better.  The loud HMF is for sale.  Scratched up, but only a few hundred miles on a repack.  It fit my 06 just fine, but not sure if it would fit an 09+.

Edited by IDRIDR

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I ordered a DG o series slip on from amazon today. I hopefully only want to take this apart  one more time,lol Where do you get the N1TC needle?

thanks

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I ordered a DG o series slip on from amazon today. I hopefully only want to take this apart  one more time,lol Where do you get the N1TC needle?

thanks

The dealer.  Or rockymountainatv.com  That's Kawi part.  The actual part number is.  16009-1912

 

Get used to taking your bike apart.  I pretty much take mine apart every mount or so.  Sometimes just to clean.

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Well i think i got this all sorted, thanks for the advise. This weekend i installed another shim under stock needle( now there's 2) installed a DG O series Slip on and a 13 tooth front sprocket. I also installed a seat concepts wide seat. This thing rocks now, does wheelies easily from a stop, haven't really tried to pop any at any speed because I'm not not made of rubber like when i was 20:). I really didnt care losing some top end with the 13 tooth, it makes this much more enjoyable to ride. If i want to go 80(or 120,lol) on the freeway, I'll take out my VTX1800S

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With my current setup which is 127.5 main jet, DG slip on, KDX300 snorkle, K@N filter, 13 tooth front sprocket, can i get more power increasing the main jet? if so would i need to change the pilot as well? The bike is great now, but if i can get more i will.

thanks for any help

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Check the color of the insulator on your plug. If it is a light to medium color of brown you are not going to do anything else in the jetting world to make a difference. If it tends to be darker or lighter then you adjust the jetting in the range you typically run in. Most likely in your case it would be the shim thickness under the needle. Be careful changing the pilot jet. If it is set in the range of one turn out up to three turn out you are fine. Based on the threads I have seen on this site very few people change them. I put a big bore kit in my 300 and went up from #35 (stock) to a #38 only to go back.

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well i spoke too soon, really didnt take the bike out on the open road and push it. It surges at about 4-5k rpm and doesnt want to go faster. It has tons on low end up until i get it up to cruising speed and then surges like I'm hitting a wall.

Can anyone help what i need to try next?

thanks

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I know when I was playing with jetting and thinking more must be better and was running with the lid off and huge pilot and main jets, I put the lid and snorkel on during a ride and the bike would do about like yours.  I think I got closer to 7K rpm, and it would just go no further.  WAAYYY too rich. Gurgle, gurgle spurt.  Black soot on the tail pipe and fender, and poor mileage.

 

I'm not saying this is the issue with yours, but, playing around with the air box lid and limiting/opening the incoming air flow could possibly help show you if this is an overly lean or rich problem.

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I kinda thought about that too after reading some threads. I have seen too lean would sputter and too rich. I have the 127.5 jet in as i was instructed by sigma. I thought i would try removing the kdx300 snorkle also air box lid and also put stock snorkle back in to see what happens before i rejet. I would prefer to go up in jet size not back down, lol.

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i was rereading this thread, my problem is only at full throttle, which is main jet. anymore ideas what i should try as well as the airbox things i mentioned i would try?

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I kinda thought about that too after reading some threads. I have seen too lean would sputter and too rich. I have the 127.5 jet in as i was instructed by sigma. I thought i would try removing the kdx300 snorkle also air box lid and also put stock snorkle back in to see what happens before i rejet. I would prefer to go up in jet size not back down, lol.

 

Why prefer to go up in main jet size and not back down?  The proper jetting will provide more power.  If you need a smaller main jet, don't get stuck on the impression that bigger is better.  If you have a lid on with KDX, stock, or no snorkel, pull the lid off and give it a try and see what happens.  If you're getting past the brick wall with the lid off, your main jet is likely too large.  Is your air filter clean?

Edited by IDRIDR

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Ya you are right, ill check it this weekend and downsize if neccesary, I got a feeling its too big

thanks

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