Question about 2005 KTM 50 SX Pro Junior LC

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What jet size should I use for and elevation of 5000 feet

My sons bike bogs down and seems like he has no low end power. just wondering if the jets might be my problem.

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6 Suggested Answers

6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

ctm72
  • 25 Answers

SOURCE: time for a top end or jetting?

sounds like the idle jet is cloged and u need to clean out the carb jets

Posted on Dec 16, 2008

  • 61 Answers

SOURCE: Jetting size 06 sx250f

jetting is not an exact procedure. too many variable altitude, temperature, humidity, gaz.. does your bike presently run rich or lean ..ect..
i would go 1 size to start. it's safe to run an engine too rich but is risky to run too lean

Posted on Jul 22, 2009

dmsr63
  • 2050 Answers

SOURCE: ktm 200sx not running right

Is your power valve clean, and moves freely? And don't forget to make sure the air filter is squeaky clean. How does the plug color look?

Posted on Aug 09, 2009

Woods Goat
  • 85 Answers

SOURCE: I bought this bike this winter, it had sat for 3

Your lower rpms are controled by the mixture screw, pilot jet, accelerator pump and the slide needle. So your problem is probably in one of these-though racing 4 strokes are known to have a little stumble at the bottom, but not what you're describing. I'll have to assume the shop has the pilot jet clean and the mixture screw adjusted properly.(roughly 1.5 turns out)

First, check your accelerator pump. Remove the carb enough to be able to look inside the throat, but leave the cables hooked up. Work the throttle a few times and make sure that there is a small squirt of fuel in the throat of the carb each time you twist the throttle. If not, your accelerator pump is clogged or damaged.

If everything is fine there, the next likely problem is the needle adjustment. It's mounted in the slide. Once you remove the needle, you'll see a small clip around it. Try moving this clip up one notch. This will lower the needle and slightly delay the fuel feed from the main. If this fuel comes in too soon, it will cause a way rich condition and cause a bog off idle.

Outside of carb issues, valve adjustment(too tight) can make for a rough idle and hard starting.

Posted on Jun 11, 2010

TerryTown
  • 292 Answers

SOURCE: i have a 2010 ktm

Thank you for contacting FixYa with your inquiry.
Low power or stalling at start is usually air/fuel related. You have taken care of most of the things that effect the bottom end power band. Some other things you might consider:

  1. Check the air vent tube on top of the tank to make sure it's not pinched or restricted.
  2. Clean the fuel tap. May have sediment or debris. Some have a filter screen. Clean it.
  3. Clean the air filter and air box. Check the rubber boot for cracks or air leaks. Clamp??
  4. Exhaust system - Check for leaks or fiber fallen from the muffler.
  5. Check the diaphragm or reed valve for cracks or reed problems
  6. Check the timing or fault with the ignition system. Is something loose.
  7. Screw in the idle jet all the way and back it out to 1 1/2 turns.
Jetting: (Tons of options with a Mikuni) In general, the main jet is for high rpms and top speed running. Needle effects the mid range to about 3/4 throttle. Idle jet effects the bottom end. 3 sizes exist 20, 25, 30.
Drill down from this link for part numbers: http://cyclehuttktm.com/FicheFinderNew/FicheFinder.aspx 2010 > 65 SX > ENGINE > CARBURETOR
Let us know if we can provide further information.
Kind regards,
TF

Posted on Jul 19, 2011

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Bike won't run smooth.


Hi, Joe if you have changed your fuel delivery system, air filter size or flow rate, mufflers or exhaust system or a significant change in altitude your carburetors need re-tuning and if your fuel system (gas tank, filters, fuel valve and carburetor) is contaminated with ethanol sludge, varnish, rust, dirt, water etc. or your bike has been sitting for months or years without running these components must be "PROPERLY" cleaned and reassembled "CORRECTLY" before any adjustments can be made. Tuning your carburetor is fairly simple once you understand the basic principals. You engine is a simple airbox sucking air in and blowing it out, it is finely tuned at the factory for maximum performance once you upset that delicate balance by changing air filters, camshafts or exhaust systems your performance may go down the and the engine may run poorly, you need to compensate the air-fuel mixture in the carburetor in order for the engine to run smoothly and at peak performance. If you are running multi carburetors you need to sync them first and make sure your air cleaner element is clean and dry for paper elements or lightly oiled for foam and meshed elements and properly installed. Here is how and where you compensate trouble: "TIP" if your engine "BOGS" your not getting enough fuel.
1. Closed to 1/8 throttle is managed by the air screw and pilot/slow jet.
2. 1/8 to 1/4 throttle is managed by the air-screw, pilot/slow jet, and throttle slide.
3. 1/4 to 1/2 throttle is managed by the throttle slide and jet needle.
4. 1/2 to 3/4 throttle is managed by the jet needle, needle jet, main jet, and air jet.
5. 3/4 to wide open throttle is managed by the main jet and air jet.
6. Wide open throttle is managed by the main jet.
If you are running lean, spark plug electrode color is white, engine runs hot and feels like it is starving for fuel you need to go up on the jet size or move the c-clip down one notch. If you are running rich, spark plug color is black or dark gray, engine runs cool, and bogs down when accelerating you need to go down on jet size or move the c-clip up one notch. When your carburetor is properly tuned for maximum performance your spark plug electrode will be a light tan color like coffee with cream. If you prefer fuel economy over performance you can go down on main jet sizes until a satisfactory level of lower performance is acceptable versus MPH, your spark plug color will be whiter and your engine will run warmer. These tuning adjustments will only make improvements if your intake and exhaust system have no air leaks or sealing issues and the entire electrical system is in proper working order and you have no mechanical issues.
For more information about your issue and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day.
Carburetor Set up 101
Carburator Theory and Tuning
KTM 250 SX 2005 Repair Manual
http://www.partsfish.com/page/oem-parts-for-ktm
KTM 250 XC Owner Manual

May 19, 2017 | 2005 KTM 250 EXC

1 Answer

Jetting on 1994 yz 250. the main jet is a 330 the pilot is a 40 and the needle is a 61. we mix the oil to 50:1 but it loads up onan idle and in the middle. we are at 5000' elevation.


Hi, Anonymous it should be noted that your performance issues are not electrical ie. faulty charging system, battery condition, and connections etc. If your fuel system (gas tank, filters, fuel valve and carburetor) is contaminated with ethanol sludge, varnish, rust, dirt, water etc. or your bike has been sitting for months or years without running these components must be "PROPERLY" cleaned and reassembled "CORRECTLY" before any adjustments can be made. Tuning your carburetor is fairly simple once you understand the basic principals. You engine is a simple airbox sucking air in and blowing it out, it is finely tuned at the factory for maximum performance once you upset that delicate balance by changing air filters, camshafts or exhaust systems your performance may go down the and the engine may run poorly, you need to compensate the air-fuel mixture in the carburetor in order for the engine to run smoothly and at peak performance. If you are running multi carburetors you need to sync them first and make sure your air cleaner element is clean and dry for paper elements or lightly oiled for foam and meshed elements and properly installed. Here is how and where you compensate trouble: "TIP" if your engine "BOGS" your not getting enough fuel.
1. Closed to 1/8 throttle is managed by the air screw and pilot/slow jet.
2. 1/8 to 1/4 throttle is managed by the air-screw, pilot/slow jet, and throttle slide.
3. 1/4 to 1/2 throttle is managed by the throttle slide and jet needle.
4. 1/2 to 3/4 throttle is managed by the jet needle, needle jet, main jet, and air jet.
5. 3/4 to wide open throttle is managed by the main jet and air jet.
6. Wide open throttle is managed by the main jet.
If you are running lean, spark plug electrode color is white, engine runs hot and feels like it is starving for fuel you need to go up on the jet size or move the c-clip down one notch. If you are running rich, spark plug color is black or dark gray, engine runs cool, and bogs down when accelerating you need to go down on jet size or move the c-clip up one notch. When your carburetor is properly tuned for maximum performance your spark plug electrode will be a light tan color like coffee with cream. If you prefer fuel economy over performance you can go down on main jet sizes until a satisfactory level of lower performance is acceptable versus MPH, your spark plug color will be whiter and your engine will run warmer. These tuning adjustments will only make improvements if your intake and exhaust system have no air leaks or sealing issues and the entire electrical system is in proper working order and you have no mechanical issues. For more information about your issue and valuable "FREE" downloads that you will need please click on the websites below. Good luck and have nice a day.
Two stroke Carburetor jetting How to performance tune your two stroke carb...
YZ250 Forward Motion Test Ride Carb Issues and Carburetor Tuning Part 26...
YAMAHA YZ250 LC Owner Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

Apr 19, 2014 | 2003 Yamaha YZ 250

1 Answer

163FML (CG200) bogging at low rev


Hi, Marcus and the usual suspects are:
1. Fuel cap or fuel tank is not venting properly.
2. Fuel filter clogged.
3. Fuel line pinched or kinked.
4. Float needle and seat sticking.
5. Float level too low.
6. Carburetor bowl vent line clogged/blocked/pinched.
7. Idle adjusting screw set too low.
8. Air/fuel mixture screw set too lean.
9. Idle port, transfer ports, slow air jet clogged.
10. Slow fuel jet clogged.
11. Faulty fuel pump.
For more information about your issue and valuable "Free" downloads that you will need please Click on blue links below. Good luck and have a wonderful day.
Bogs when open the throttle fast
Motorcycle Message Board Motorcycle USA
boging and half throttle
boggs down when accelerate aggressivly to full throttle Pit Bike Club
Why is the engine bogging under acceleration Suzuki FA50 Moped
Bike dies when you give it throttle

Mar 17, 2017 | Motorcycles

1 Answer

I put a cometic headgasket on upside down in my sons 2005 cr85r


the rejeting of the bike is most likly the cause of the sputtering. Maybe the size of the jet doesnt suit the altitude check to see that the jet is not too big.

Sep 18, 2012 | Honda Motorcycles

1 Answer

Just bought a 2001 WR 426. Has an FMF pipe, no air box lid. Main is a #165 and pilot is a #42.these are stock jets according to shop manual. My elevation is 2500-3000 Ft. Any ideas on jetting?


Hard to give accurate info with out seeing the bike with jetting but I would suggest take a reading from the fuel air screw if the bike running better with the fuel air screw in carbi at 2.5 turns out or more then definitely increase pilot jet up 1 or 2 sizes if you get the bike to run well between one - two turns out on the fuel air screw that is where your jetting should be
I wouldn't be concerned with main jet at all - it should be fine for wide open throttle unless you feeling power loss when you open it right up
also if you are getting backfire or popping when de accelleration that also hints toward lean pilot so a size or two change in pilot jet would be worth trying

Jan 20, 2011 | 2001 Yamaha WR 426 F

1 Answer

I have had the bike since 2006 and it ran great love the bike. i bought it used with vance and hines sstraight pipes sounds great! never had a power issue is any gear at any speed i took it in for...


If they replaced the jets, did they replace them with the correct size? First off, the metering jets do not wear. Ethanol does not wear jets. If they replaced them, they replaced them to change the mixture. I would have them replace the jets with the original jets. Now, if something is going to wear, it the "needle jet" which isn't really a metering jet. It's the jet that the needle slides in when the slide in the carb goes up and down. It will wear due to the rubbing of the needle against the inside of the jet towards the engine side of the jet. Again, someone it telling you a story. Ethanol will not wear a brass jet. They changed the jet to change the fuel air mixture and now it's not right.

To find out which way it's wrong, try taking the air filter out of the air box and ride the bike at the speeds you have the problem. If the problem gets worse, you are jetted too lean. If he problem gets less severe, you're jetted too rich. By removing the air filter, you're allowing more air to get into the carb leaning the mixture. Now, since at this speed you are not a Wide Open Throttle, you're still running on the needle in the mid-range of the RPM range. You can lean the mixture by lowering the needle and richen the mixture by raising the needle.

What you need to do is take the bike to someone with an Exhaust Gas Analyzer and a Dyno. They should be able to put the load on the bike exactly like it's on the road and check your fuel air mixture at any given RPM. This will tell them if you're too rich or too lean and the RPM range will tell them which jet to change or the needle position to change.

Ethanol does not wear brass jets. The shop screwed up the mixture on your bike, that plain and simple.

Good Luck
Steve

Aug 25, 2010 | Yamaha Road Star Silverado Motorcycles

1 Answer

Main jet and needle setting for 2003 honda cr250 at 5000 ft elev.


this should get you close, will still have to fine tune due to exacting conditions.....humidity, temperature, pipe, silencer and reeds....however try this:

Main 360
Pilot 20
Needle H1-70
Needle Top Clip
Air Screw 2 Out



Oct 08, 2009 | 2003 Honda CR 250 R

1 Answer

Yz 150f bogs when you give full throttle all at once


ok, assuming you replaced the carb header and stator with aftermarket parts, then I would say you definitely have a jetting issue. that flat spot is coming from your engine starving for fuel. its taking the gas too long to get from the carb to the engine. you would fix this by adjusting the idle mixture on the carb. the first thing I would do is look for the fuel mixture screw on the carb. im not familiar with your specific model. but the screw is usually found facing down on the bottom of the carb, directly in front of the bowl. when you find it, turn it counter clockwise about 1/2 turn at a time until that flat spot fades away. if that doesnt work, then you will need to up the size of the pilot jet inside the carb. maybe 1 or 2 sizes would be enough. if you replaced the carb with a bigger carb, then you may not be able to fix this problem. in my experience, larger carbs will increase power, but usually throttle response, especially low end, suffers considerably. the reason for this is lower intake velocity and vacuum. basically, with a bigger carb it takes a second longer for the fuel to be drawn from the carb and properly atomize with the air. hope this helps.if I overlooked anything let me know! some more info on the engine/modifications and carb/jet sizes would help too. good luck.

Sep 06, 2009 | 2004 Yamaha YZ 250 F

1 Answer

Jetting


WHAT MEAN JET? : Carb jetting can be easily understood if we understand the basic principles of carb and engine operation. A carb mixes fuel with air before it goes into the engine. When the mixture is correct the engine runs well. The bottom line is a carb must be adjusted to deliver fuel and air to the engine at a precise ratio. This precise ratio can be affected by a number of outside and inside influences. If you are aware of these influences you can re-jet your carb to compensate for the changes. I'm going to show you some examples of how you can change your jetting for better performance and in some cases increased engine life. As with any engine work be sure you have good tools the correct parts and a good manual before you get your hands dirty! ALTITUDE COMPENSATION: For our first example let's say we find a new riding area WAAY up in the mountains. Our jetting is dialled in for our usual riding area which ranges from sea level to 1500 feet. Our NEW riding area starts at 4000 feet and goes up from there. Going to a higher elevation will require will require a jetting change but which way? Like our fuel density air density can also change. Higher elevations have less air density then lower ones. At high elevations our engines are getting less air so they need less fuel to maintain the proper air/fuel ratio. Generally you would go down 1 main jet size for every 1750 to 2000 feet of elevation you go up (info for Mikuni carbs). If you normally run a 260 main jet at sea level you would drop down to a 240 at 4000 feet. Something else goes down as you go up in elevation is horsepower. You can figure on losing about 3% or your power for every 1000 feet you go up. At 4000 feet your power will be down about 12%-even though you rejetted! For our second example let's say we are still at our new 4000-feet elevation riding area and a storm comes in. We head back to camp and ride it out overnight. The next day there's a foot of snow on the ground the skies are clear and it's COLD!. Aside from getting the campfire going and making some coffee you should be thinking about jetting again! Cold air is dense air and dense air requires bigger jets. If the 240 jet ran good the day before you will need a bigger jet to run properly today. If the temperature is 50 degrees colder,,

Nov 10, 2008 | 2005 Hartford VR 200X

1 Answer

Jetting


WHAT MEAN JET? : Carb jetting can be easily understood if we understand the basic principles of carb and engine operation. A carb mixes fuel with air before it goes into the engine. When the mixture is correct the engine runs well. The bottom line is a carb must be adjusted to deliver fuel and air to the engine at a precise ratio. This precise ratio can be affected by a number of outside and inside influences. If you are aware of these influences you can re-jet your carb to compensate for the changes. I'm going to show you some examples of how you can change your jetting for better performance and in some cases increased engine life. As with any engine work be sure you have good tools the correct parts and a good manual before you get your hands dirty! ALTITUDE COMPENSATION: For our first example let's say we find a new riding area WAAY up in the mountains. Our jetting is dialled in for our usual riding area which ranges from sea level to 1500 feet. Our NEW riding area starts at 4000 feet and goes up from there. Going to a higher elevation will require will require a jetting change but which way? Like our fuel density air density can also change. Higher elevations have less air density then lower ones. At high elevations our engines are getting less air so they need less fuel to maintain the proper air/fuel ratio. Generally you would go down 1 main jet size for every 1750 to 2000 feet of elevation you go up (info for Mikuni carbs). If you normally run a 260 main jet at sea level you would drop down to a 240 at 4000 feet. Something else goes down as you go up in elevation is horsepower. You can figure on losing about 3% or your power for every 1000 feet you go up. At 4000 feet your power will be down about 12%-even though you rejetted! For our second example let's say we are still at our new 4000-feet elevation riding area and a storm comes in. We head back to camp and ride it out overnight. The next day there's a foot of snow on the ground the skies are clear and it's COLD!. Aside from getting the campfire going and making some coffee you should be thinking about jetting again! Cold air is dense air and dense air requires bigger jets. If the 240 jet ran good the day before you will need a bigger jet to run properly today. If the temperature is 50 degrees colder,,

Nov 10, 2008 | 2002 CCM 604 DS Dual Sport

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