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2008 300XC Jetting

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Hi Guys:

I searched this forum and found a few answers however I thought I'd check to see if anyone in my type of climate has the jetting down for this bike!

I ride mostly around 2000'ASL, usually in temps around 20C to 30C (around 80F?); currently stock jetting.

At the end of my first heat cycle the bike was leaking gas like crazy; gave the bowl a few knocks but no luck, still leaked. After the second heat cycle it stopped (?); I've read that some have adjusted their float level however could mine just had been stuck?

When it's on the pipe it goes like crazy however before that it's not very smooth. Should I try the N3CH needle and if so, at what clip position? Pilot jet recomendations? And lastly, would moving down to the 162 main that I got with the bike be too lean? Guys seem to be using them however the manual suggests reserving that main for quite high elevations. Plug's a bit oily but not too much spooge out the pipe.

I'd appreciate any help you can pass my way!

Cheers!

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Install the N3CH or EH. The EH is half a clip richer than the CH. Do a plug chop on the main jet before changing it out. The pilot jet is usually kept stock. Start with the needle in the middle clip (3).

It wouldn't hurt to adjust the float level as well.

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GMOSS thanks for the info! Sorry, but what do you mean by a plug chop on the main jet? I've never adjusted the float level before either, wondering if there's a tutorial or something out there to show the process?

Cheers!

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Plug chop: fresh plug, close to WOT in 3rd gear, pull the clutch letting it calm just a second and shut it down, pull the plug for a read. If it's black - rich, tan - just right, white - too lean. You can do the same for the pilot, but 35 is the smallest pilot available, and it's stock in your bike, I believe.

Adjusting your float level should be outlined in your manual, and there may be some info in the pinned thread at the top of this forum.

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I'm using a jd jetting kit. I have a 162 main and using the red needle 4th clip down. I went up to a 38 pilot seem to give the bike a little more low end torque and seem to help my overheating problem too. Not sure what jd's equates to as far as ktm part number. Most of my riding is around 2000-4000ft.

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Ive tried the Ch and EH needles but the 08 seems to really like the optional needle the N2zW in #2 or 3 with a 38 pilot and a 162 main, that should get you in the ball park give it a shot and see how you like it, red spring a few turns in from flush.

Mike

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Dave Go to your owners manual and set your jetting for your temp./altitude,Go to KTM and buy the ignition module for 250sx. The new ignition module will take away all the bog and heisitation that you are trying to tune out with jetting. In Canada the module cost me about $220 from Blackfoot motorsports. Remember absolute power corupts absolutely.

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Thanks for the advice! I've never heard of that as an option, could be worth a try!

Cheers, Dave

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Dave Go to your owners manual and set your jetting for your temp./altitude,Go to KTM and buy the ignition module for 250sx. The new ignition module will take away all the bog and heisitation that you are trying to tune out with jetting. In Canada the module cost me about $220 from Blackfoot motorsports. Remember absolute power corupts absolutely.

I havent heard of that...What did you notice when you swapped boxes? Did you do this swap on an 08' 300? Were you still able to retain the mapping ability?

Can you elaborate on this a bit?

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Just my 2 cents....

My bike would not jet clean, period until i had about 10 hours on it. Dont know if it is a KTM thing or if i am just imagining things but after the magic 10 hour mark, things started gettin' cleaner.

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The 300xc power module curve was designed to be very controlable in all different terrain. This makes it a very forgiving trail/harescramble bike. I bought a new 08 XC in Brooks, Alberta and while i was waiting for delivery i met Joel waiting for delivery of his 250sx. He told me the new 300 was boggy and if i wanted to get it all (from the engine)i should trade out the module. I forgot this advice. I ran my bike for 10 hours or so and fouled 3 plugs on the stock jets that came in the bike. I phoned back the dealer to bitch and he said to swap out my original jets to the other supplied in the kit with the power valve springs. He said "The first jetting is a rich set up to help with seating the rings and break in." I put in the 162 main jet and n2zj needle at 3 position. Also opened the air screw 2.5 turns to stablize at low rpm. The bike responded way better and i was happy. Ran faultless for 10 hours but things still seamed boggy at the low end. You crack the throttle and wait for it to spool up, then once it makes it 1/3 the way in the rpm it starts to pull. I read about this majic needle N3ch that was cleaning up the kawasaki's so i installed it too. A little better, maby. I took my 11 year old son for a ride at blackfoot motor park and met 250sx Joel again. He was practicing for an upcoming race. He and a 300xc friend had gone to McClean creek for a little mountain riding. They swapped modules and the 300 rider didn't want to give it back, it was that good. So i bought one. KTM part #54839031800. The swap is simple ,cut the plastic zip tie, use a flat blade screwdriver to pry open the plastic latch and remove. Go back to the stock jetting carb table in your manual. You can probably go one setting leaner safly to get the most power. This has been the biggest power gain to date. No more waiting for the engine to spool up. This is not a psycological power gain, you won't need a dyno to tell the difference. This is Crack the throttle and hang on. The map switch still works.The one thing i have noticed is no matter what i do the 300 still pings a little in the pipe under hard decelleration. what i mean is if you are coasting down hill the pipe still goes pop,pop ,pop I thought that it was an indication of poor tuning. The more i read the more normal it is for a 300, its called 300 pipe bang. Hope this answers your questions.

, Bill.

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The 300xc power module curve was designed to be very controlable in all different terrain. This makes it a very forgiving trail/harescramble bike. I bought a new 08 XC in Brooks, Alberta and while i was waiting for delivery i met Joel waiting for delivery of his 250sx. He told me the new 300 was boggy and if i wanted to get it all (from the engine)i should trade out the module. I forgot this advice. I ran my bike for 10 hours or so and fouled 3 plugs on the stock jets that came in the bike. I phoned back the dealer to bitch and he said to swap out my original jets to the other supplied in the kit with the power valve springs. He said "The first jetting is a rich set up to help with seating the rings and break in." I put in the 162 main jet and n2zj needle at 3 position. Also opened the air screw 2.5 turns to stablize at low rpm. The bike responded way better and i was happy. Ran faultless for 10 hours but things still seamed boggy at the low end. You crack the throttle and wait for it to spool up, then once it makes it 1/3 the way in the rpm it starts to pull. I read about this majic needle N3ch that was cleaning up the kawasaki's so i installed it too. A little better, maby. I took my 11 year old son for a ride at blackfoot motor park and met 250sx Joel again. He was practicing for an upcoming race. He and a 300xc friend had gone to McClean creek for a little mountain riding. They swapped modules and the 300 rider didn't want to give it back, it was that good. So i bought one. KTM part #54839031800. The swap is simple ,cut the plastic zip tie, use a flat blade screwdriver to pry open the plastic latch and remove. Go back to the stock jetting carb table in your manual. You can probably go one setting leaner safly to get the most power. This has been the biggest power gain to date. No more waiting for the engine to spool up. This is not a psycological power gain, you won't need a dyno to tell the difference. This is Crack the throttle and hang on. The map switch still works.The one thing i have noticed is no matter what i do the 300 still pings a little in the pipe under hard decelleration. what i mean is if you are coasting down hill the pipe still goes pop,pop ,pop I thought that it was an indication of poor tuning. The more i read the more normal it is for a 300, its called 300 pipe bang. Hope this answers your questions.

, Bill.

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What makes the 250sx CDI power module different to the 300xc CDI power module curve?

Byte

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Who else has done this mod on their 300?

Byte

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Dave Go to your owners manual and set your jetting for your temp./altitude,Go to KTM and buy the ignition module for 250sx. The new ignition module will take away all the bog and heisitation that you are trying to tune out with jetting. In Canada the module cost me about $220 from Blackfoot motorsports. Remember absolute power corupts absolutely.

I run the SX black box on my 525, been thinking about trying one on the 300, after reading this i think I will, even though I have no issues at all with my 300 once i had Dick's racing oval bore the carb and get the squish in line.

Mike

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