Trying to figure out the jetting on my 2007 250 XCW.  Took the bike up to higher elevation and started having issues.  Dropped the needle from the #3 to #2 position and the bike ran okay, but was fouling the plug.  The air screw was only out about 1/2 turn.  I went from the N8RH to the N8RW needle which the book recommends on the chart for higher elevation and kept the clip in the #2 postion and still had to keep the air screw out only about 1/2 turn from seated to keep it from falling on it's face when I blip the throttle at idle.  Still seems like it's running rich based on the look of the plug and still fouling the plug at times.

I read that worn Reeds could cause a rich condition . . . Okay guys . . . I've got the reeds in my hand . . . I don't see any signs of severe wear like chipping or fraying, but it if I hold it up to the light, I see dots in lines almost like perferation holes.  It's more noticable on the upper edge.  Is that normal/okay?

I also read that if the float is too high it could cause a rich condition so I pulled the carb out too and figured I'd do my best to check that and see how the float needle looks while I'm at it.  Any tricks?

So based on what I've read, if the air screw is out less than a turn, you need to increase the size of the pilot . . . okay, makes sense (bigger hole allows more gas, unscrewing the air screw more allows more air to balance it out), but, I'm running a 35 which is what the book recommends for pretty much everything except really cold sea level riding. I figure I'll try the other things first.

Tired of chasing the jetting down and think if I can get it right, I might unlock the magic my bike has been missing . . . I was messing with it the other day and it just came alive at one point, was popping wheelies, and just felt super strong, took it up to LPNF yesterday and it was back to feeling sluggish.


Want to have it set up for 5-9K feet and 75-90* temps . . . Kennedy Meadows and LPNF for you SoCal guys.

Current set up:  35 pilot, N8RW needle in #2 position, 158 main, air screw 5/8 turns from fully seated.

You need to drop you main jet down one size for the combination of higher altitude and higher temperature.
Then you can adjust/change your needle for throttle response.

I would recommend following the below guideline, co-written by Eric Gorr, the best two stroke tuner out there.

'GOLDEN RULES':



Checking the Main Jet– Warm up the engine and go for a short ride letting the engine comes up to its normal operating temperature. Install a brand new plug that's been properly gapped. With the new plug installed aggressively accelerate through the gears until you reach 4^th or 5^th gear. For best results you should accelerate up a slight up hill section to place additional load on the engine. Continue to run the engine at WOT for 20 to 30 seconds longer if there is not fear the engine is running lean. If you suspect the engine is running lean 15 to 20 seconds to give you an indication. At the end of your full throttle run simultaneously push the kill button, chop the throttle and pull in the clutch. This procedure is often refereed to as a " plug chop". It is important to perform a plug chop exactly as described. If you allow the engine to run or leave the throttle open for even a few seconds after the plug chop the plug reading will be invalid. Now remove the spark plug and carefully look at its color.

Now, about the CORRECT WAY to read a plug!:

"]Plug Reading -[/size][/font
What does a good plug look like? First you need to know where to look and what to look for. I’ve seen a lot of plug reading instruction that suggest you to look at the general appearance of the plug. That doesn’t work. The easily visible portion of the plug, the upper part of the porcelain and the electrodes, won’t give you an accurate reading. This area is mostly affected by additives in the gasoline and the oil you’re running. To get an accurate indication you want to look down inside the plug where the porcelain insulator emerges from the steal body of the spark plug. Ideally you should see a ring of light brown/tan at the lower 1/4 of the porcelain.White is lean and you’ll need to install the next richer main jet( larger number ) and do another plug reading. A dark brown to black ring is too rich and you’ll need to install the next leaner main jet ( smaller number ). A small flashlight and magnifying glass make this much easier to see and it’ll give your friends something to poke fun at. If you ride in a diverse area with fluctuations in temperature greater than 15 degrees F, and altitude changes dropping more that 3000 feet over the course of the day or you ride in high load conditions ( loose sand, mud, long steep hills ) adjust the size of your main jet until you reach the ideal condition then install the next richer main jet which should result in a dark brown plug reading. You'll be loosing a small amount of top end power in trade for the added confidence that you can ride aggressively over the course of the day without fear of running lean at WOT.ond"
]
Checking the Jet Needle [/font]– Once you have the main jet properly sized you can turn your attention to the jet needle. Warm up the engine and go for a short ride until the engine comes up to its normal operating temperature. Install a brand new plug that has been properly gapped. With the new plug installed accelerate through the gears until you reach 4th gear. For best results you should find a location that allows you to run safely at half throttle with out having to ex or decelerate to avoid obstacles etc. A long straight away or well groomed oval track will work the best. Continue to run the engine at half throttle for more than 60 seconds if possible. Do a plug chop and inspect the plug. If the plug indicates a lean condition, lower the clip on the needle by one position. Lowering the clip by one position raises the needle further out of the needle jet allowing more gasoline to flow, richening the circuit. If the plug is dark brown to black raise the clip’s position by one notch to lean the circuit. As a general rule if you need to run the clip in the top position you should install a leaner jet needle. If you need to run the clip in the bottom position you should install a richer  jet needle. Jet needle selection is something of an art. Watch for an article in the near future describing PWK jet needle profiles in more detail.  This method will give you a good ball park indication if you jet needle is properly sized.  However due to inefficient cylinder scavenging at lower throttle settings its often little more that a ball park indication and you'll need to fine tune by feel.
Once you're satisfied with the appearance of the plug turn to the jetting by feel method to fine-tune the circuit. Gradually roll the throttle open from 1/2 to 3/4 throttle paying particular attention to the sound and the type of power delivery. Having an experienced friend on the sidelines to listen and watch the silencer for excessive smoke is also helpful. A rich condition will result in excessive smoke from the silencer, the plug will often carbon foul and the engine will produce a sputtering/crackling sound. A lean condition will result in slow throttle response, you twist the throttle but the power delivery is lethargic and flat. A lean condition results in a tell tale booooooha sound as well. You can quickly verify a lean condition by pulling the choke half way out. Engaging the choke will deliver additional fuel to the system and the symptoms of a lean condition should clear up.

Edited by Krannie, 01 July 2012 - 05:41 PM.

Your reeds are probably fine.  Severely worn reeds will cause the bike to misfire/bog and/or run rich.  Mine would bog at full throttle.  I thought I was running rich but finally found the reeds were bad.  If you having a rich jetting problem, first try lowering the jets/needle and the very next thing check the reeds.   I like to do the "water test" on reeds.  Fill them up with water if they completely drain in less then 15-17 seconds I would replace them.  My new ones drained in about 20-23 seconds.  My old ones with minor fraying on the edges drained in 9-11 seconds.  The light test doesn't really work well.  My new ones let in just as much light as the old ones but they actually sealed much better.  Also try lightly sanding the reed cage to get a better sealing surface.

Krannie, on 01 July 2012 - 05:39 PM, said:

As far as the main jet . . . stock was a 162 . . . when I got it Z Racing had put a 155 on it . . . I'm thinking that may be why it seemed to fall flat at speed out in the dez . . . I went to a 158 as that's the books recommendation for areas/temp like KM & LPNF.  Do you think I should drop it back to the 155?

I've read those instructions, but I've really been trying more to dial in the bottom end . . . you've seen me ride . . . unless were out in the dez or I'm trying to gun it up a hill, when am I ever at even 3/4 let alone WOT???  That and I have to take the tank off to change the spark plug and there's not really any place here around my place for me to really get the thing going like they instruct.

I've seen those and other similar

maxamillion125, on 01 July 2012 - 06:01 PM, said:

I'll give the water test a try.  Can you elaborate on sanding the reed cage to get a better sealing surface?  Besides the tiny holes in lines, I can see lines on the sides which look like tiny gaps.

Update:  I did the water test and FAILED!!!  Looks like the tension on the bottom flaps is way lower than the top ones and those two drain very fast.  The top two hold pretty well and aren't fully drained for about 20 seconds, but the bottom two are at the half way point as soon as you take it out of the water and are fully drained in 10 seconds or so.  Would this explain or contribute to the bike running rich and fouling the plug?  And how do I fix it or do I need a new one?  The manual I have looks to have a different set up where there are screws that hold on the flappers but mine is a VForce 3 and it doesn't look like you can take it appart.

Lightly sand the reed cage edges where it contacts the reeds, the sealing edge.  Take out the reeds and use fine sand paper probably 160 or 240 grit.

You have to push the little plastic rod out of the bottom of the reed cage.  It takes a good amount of pressure to push it through.  You should be able to find some directions online.  When my reeds were bad I fouled plugs if I let it sit and idle more then a minute or two.  Sounds like you found your problem.

Edited by maxamillion125, 01 July 2012 - 06:55 PM.

So I figured out how to tear the reed cage all apart and how to remove the petals.  I thought maybe I could turn them over and maybe they would seal better that way, but now the whole thing drains in about 10 seconds vs. just one side like it did before.  So do I just replace the pedals or do I need to replace the whole thing?

I see the petals listed on the OEM guide for over 100 bucks, but see the petals listed all over for 60 bucks for the VForce3, just not for my KTM . . . what is the deal . . . because KTM chose to use the VForce I have to pay OEM prices for the same stuff?  What is the trick?

Edited by schmo, 01 July 2012 - 09:05 PM.

Just replace the pedals, I found them for $80 http://www.ktmpartsh...=2007&fveh=9758

Seems like the water is flowing out the small gaps around the petals and the cage.  The petals look to be in good condition without any fraying, chipping, etc.  Will new petals seal better or will I have the same issue?

Schmo; you and I have the same bike (and VF3 reed cage).  I had the same issue with one of the reed keepers.  They wear out.  The prevous owner had what looks like a thin layer of silicone on the keeper to compensate.  The people at Moto Tassinari told me this issue was not all that uncommon with their VF3.  Check out the VF4 on their website and you'll see how they improved/fixed it.

Recruit, on 02 July 2012 - 11:23 AM, said:

Did you need to replace the whole thing then or just the petals?  I don't want to buy the petals and end up with the same issue if the actual cage is the issue.  And did you replace it with another VF3 or the VF4?  I thought I'd read on KTMTalk about some guys having issues and switching back to the VF3 after trying the VF4.  I don't know if the photos are correct or just stock photos that don't match the actual item, but I've seen pics of VF3 cages that look quite a bit different than mine.  Also noticed that when I try to seach for the VF3 or the replacement petals, they don't come up for my bike unless I search thru the OEM parts list which is way more expensive.  I can find the entire VF3 for 150 bucks all over the place, just not for my particular bike.  

I'm fortunate to have two 07 250xcw's; both of course with VF3's.  I'm using the better of the two in my primary ride.  The guy at MT said I'd probably be better off going with the VF4 instead of new reeds for the VF3 since the cage was already worn.  $150-$160 isn't cheap to me for a new VF4 but will probably go this route once the second VF3 wears out.

Not sure about different variations of the VF3.

Edited by Recruit, 02 July 2012 - 12:51 PM.

I tired to clean up the cage and petal edges with some 600 grit but it didn't make a difference as far as the water test goes . . . seems like the bottom two sections drain about twice as fast as the top two.  Is the water test the tried and true method to test the Reeds?  The cage and petals look fine with no chipping or fraying like I've seen on-line.

Not sure if water is the tried and true method but believe any gap between reed and cage will result in power loss.  More the gap = more the loss.  Too large a gap and the engine may not even start.

I'd give a thin layer of high-temp silicone between the keeper and reed a try.  Probably not a long-term solution but could at least confirm if a worn cage is the culprit.

I think I'm going to go ahead and try the VF4 after reading up on it a bit.  A new VF4 is about 150 bucks whereas just the new petals for my VF3 would be 80-100 bucks and I just don't have much faith that new petals will make much of a difference as the petals I have now look really good and even after flipping them over and swaping them around it's still the same two chambers on the bottom that are draining quickly.

Pulled the trigger last night on the VForce 4 Reed Valve.  Anybody used PowerSportJunkie before?  Best price I could find anywhere for it . . . 125 bucks and the had a coupon for a few bucks off, so the cost of the "new and improved" V4 was only 20-40 bucks more than just replacing the petals on my V3, where I still would have been doubtful that the seal would have been good.  Hopefully the parts ship fast and this does the trick.  I need to figure out how to double check my float bowl height and want to check the needle tip to make sure it's not worn, but from what I've read, that's really all I can think to do.  Gonna do that and then recheck the jetting and will bump up the pilot jet one size if I'm still only turning the Air Screw out a half turn or so.

Nice schmo!  Let us know how the VF4 does.  One may be in my near future too so will be curious to hear how it works for you.

Hi Joe I read a while back that the first V4s were bad.  When you get it, you may want to check that the pedals don' hit on the cage and prevent full opening.

Anybody got a good write up/video on setting/checking the float height?  I want to check that and also want to check the condition of the float needle as those are the only other things I can think to check to see why I seem to be running rich, yet have to close the air screw down so far.

bnr, on 06 July 2012 - 01:54 PM, said:

I read something about the first VF4s being bad too, but it sounds like they have addressed the issue, I'll double check to make sure I didn't get a bad one.

Edited by schmo, 06 July 2012 - 04:29 PM.