2 stroke ktm 250 making me grey HELP

Hi All

 

Please help, I bought a second hand ktm non running, I eventually got it running but it bogged badly and then just started revving. I read as much as I could online and came to the conclusion that I need to lift the needle one up. Which i did but now it revs to the max once i start it and cant seem to effect any change by changing air fuel mixture screw or with idling screw, If i set the needle back down to the last ring i will have the same problem as i had initially. I want to get the bike running, sell it and buy a much newer ktm 250.

 

Looking forward to your replies.

 

Cheers Justin

First thing first, where do you ride, elevation, air condition and such.

Second, what's your current jetting: pj, mj and what needle at what clip; where's a/s screw setup, etc.  For a used bike, I'd take apart the carb and clean it well as first step.

Third, have you changed the spark plug?  If not, take it out and check it.  If you don't know how to check it, just take a picture and post it here.  I'm sure there will be plenty of people will provide good advice.

Remember, jetting is a multi-step process, or you can go buy a jetting kit and fine tune it quicker.

Hope that helps.

Hi Flywheels

 

I ride at the ocean/sea level mostly technical but have not ridden it as yet due to problems, please explain pj and mj and how to check, and not sure what the current needle is it is on the second clip from the top, I have cleaned the carb made sure all the jets are open and everything crustal clean, I have a newish plug in been testing the bike with will send pic. last thing loads of oil muck coming out of the exhaust. happy to go through the process now and learn as much as possible. appreciate your assistance.

No problem, we all start from somewhere.

pj: pilot jet (there is a number on the jet that tells you the size)

mj: main jet (same as pj)

a/s: air screw (the position is when turned all the way in VERY GENTLY and back out, say 1 turn or 1.5 turns, etc)

If you want to learn about jetting, may I suggest you to go to youtube and search for 2 stroke jetting.  There are some good videos there.  That should get you a starting point.

Also, I'm sure there are jetting tech threads in this forum that you should do a search at jetting section.

Best luck.

 

Vincent

Edited by flywheels

The idea behind jetting is to create the correct ratio of fuel to air in your engine. It is dependent on the atmospheric conditions in which you are riding since you can not control those variables. As temps and elevation change you will need to adjust your jetting.

 

I suggest finding out what KTM recommends for your bike/temperature/elevation combination and start from there. There is a chart, likely in the back of the owners manual, that tells you what each variable should be for any given temp/altitude combo.

 

There are 5 basic variables for you to adjust: pilot jet, main jet, needle, clip position, air screw position.

Sounds like you have an air leak. Find that before you worry about messing with your jetting.

Sounds like you have an air leak. Find that before you worry about messing with your jetting.

Yup. Guessing it is the main seal on the clutch side of the crank. That would explain the unresponsive carb adjustments and excessive spooge (oil muck).

Edited by Jethrobolas

I bet after you made the needle adjustment something caused the slide to stick open, which is causing your bike to run wide open. One night I putted around my yard on my 125, loaded it on the trailer, went to the track the next day and when I kicked it it ran wide open. I didn't touch the bike at all and somehow the slide stuck.

 

Make sure the power valves are clean on the bike.

 

 

And it sounds like the rest of your issues just comes down to carb adjustments...Clean, re-jet, dial in.

Edited by dan2581

Hi all, one Step at a time, if it is a air leak how do I check this prior to taking the engine apart, could the spooge come from incorrect settings on the carb?

There is a hairline crack on the slider in the carb, going to replace prior to doing anything else.

All the jets are stock standard.

Hi all, one Step at a time, if it is a air leak how do I check this prior to taking the engine apart, could the spooge come from incorrect settings on the carb?

There is a hairline crack on the slider in the carb, going to replace prior to doing anything else.

All the jets are stock standard.

 

If your slide is cracked, thats probably where your air leak is. At least that would make sense in my mind.

 

If you want to check for other vacuum leaks, with the bike idling spray brake cleaner around all the engine seals, air boot, carb seals, and if you do have a leak it will suck in the brake cleaner and the idles will rev up a little bit. You can track down the spot by finding out where your spraying when the idle rises. But it sounds like to me your slide is just junk.

Hi all slider replaced bike idles, will take it for a ride tomorrow and then give proper feedback. asked the mechanic at the shop to check jetting and he explained process in detail, current jetting 100%

Hi All

 

Bike ran like a dream have to get the air fuel mix right was a little slow to get going in first but once powerband is hit beautiful. have order rings and head o ring, because the coolant fluid started running out and assuming the head gasket/ o ring is blown.........

Hi All

Bike ran like a dream have to get the air fuel mix right was a little slow to get going in first but once powerband is hit beautiful. have order rings and head o ring, because the coolant fluid started running out and assuming the head gasket/ o ring is blown.........

Change the oil. If it is milky grey your impeller seal is probably leaking coolant into the gearbox, it is an easy fix if it is worn.

Change the oil. If it is milky grey your impeller seal is probably leaking coolant into the gearbox, it is an easy fix if it is worn.

What and where is the impeller seal?

What and where is the impeller seal?

First change the oil and see if it even needs to be addressed

Hi drained the oil, looks okay do I leave it?

So the oil pic, first is resting second was whilst it was coming out, new rings and gaskets, o rings will cost me just over a $100, would prefer not to but will if i have to, opinions all.....

DSC_0133.jpg

DSC_0131.jpg

"please see oil pics and give opinion thanks Justin

Its not milky grey. So your impeller seal is good.

Hi all, want to thank everybody for their assistance, took the head off just for in case and found that it had one o ring seal short, separating coolant from piston. Also noticed that the piston head is finished. added a pic of the top. Thanks and cheers.

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