2000 KTM 250 Exc

[csdwarf]

I bought the bike fully rebuild, i have all reciepts and all parts to prove rebuild, the local machine shop rebuild it.


everything about the bike is perfect, i love it, but i have one quest



- When im decelerating or holding a steady speed and throttle.


the bike pings, like ting, ting ting, the 2 stroke thing, but it jolts the hole bike and seems to make a "slap" like noise.


i have a trail tech vapor and i have 20 hours on the bike, so i dont think its a big problem, and i know KTM has some weird noises, like clutch growl.


is this just another noise?

 

[csdwarf]

I think what my bike is doing is "Surging" at idle and when im coasting.(Only when bike is warmed up)

this is a sign of lean condition correct? what do i adjust to try to stop this?

 

[dirt bike dave]

If you suspect a slightly lean condition at low rpm, it should be easy to adjust the air screw (turning in will make it richer).

You could also experiment with needle settings. Moving the clip to a lower groove will richen it up.

If the previous owner dialed in the bike for a higher elevation than you are riding at, you may need to make a few adjustments to richen the jetting.

Sometimes a sharp jolt at low rpm can be a sign you a lugging the bike at too low an rpm, and it wants to be downshifted.

 

[csdwarf]

I really only notice it when i get 10 miles into the trip, my engines up to temp and stop to wait for a friend or talk, its like "Room, room, room" pulsing.

when i'm driving everything seems great, great power, and when im in the top end i actually get a little spoog, so i think its decently jetted in the top end.

ill do some plug chops when i get this high idle/ surging rpm idle figured out, dial everything.



i do think it is the air screw, honestly. easy to try.

That is on the outside of the carb right? not inside the float bowl? i havn't really looked my carb over. ill know what it is when i look though, obviously not the slide stop.



thanks for your response, i hope im explaining myself clearly its a bit hard to explain, so thanks a lot :D!

 

[dirt bike dave]

The airscrew is usually on the left side of the carb, toward the rear. It is on the main body of the carb, just above the float bowl. You usually need a pretty small blade screw driver to adjust.

Measure where it is now by turning it all the way in and counting the turns.

On most bikes, if the air screw is more than 2 or 3 turns out, it won't make any difference if you keep turning it out further.

Try resetting it about 1/2 turn in from where it is now, and see if it makes a difference.

 

[csdwarf]

ill try that when it stops raining, but does what I think make sence?


why would the bike only "Surge/rev up higher" when its warm.


i cant see what else it would be, the idle is fine when the bikes cold, just when she gets up to temp it starts acting lean at idleish rpm


should i adjust it while the bike is running on a stand(warmed up idling high)

or should i just give it a 1/2 turn(in) and go for my daily rip and see if it fixes it?

thanks!

 

[csdwarf]

Alright, i went to adjust it, and it was about 1/4 of a turn out, so i turned in almost all the way in, like 1/64 of a turn out.

 

[dirt bike dave]

You may want to find out what pilot jet is in there and get the next step richer. Moving the needle clip one position is also something to experiment with.

Sounds like the bike's jetting may be more suited for higher elevation or warmer temps than your current conditions.

It's probably pretty close, though, if it runs good and only shows a few minor indications of being lean. Just a little fine tuning, that's all.

As to the earlier question, in my experience, a bike when warm and at operating temp will absolutely show more signs of being 'lean' than when cold.

 

[csdwarf]

is the easiest way to see what the pilot jet is to take the carb apart and look?

its labeled correct?


how big of a difference does temperature make? because its the beginning of the season, and its 40-60 degrees when im riding. in the mid season its much warmer,

probably 70-90.

its not bad to run the bike a little lean is it? im not going super hard on it ect..

 

[csdwarf]

Ive been reading other posts about this, and there seems to be some other people that have had the same problem.


A lot of people are saying air leaks, but that's hard for me to believe because i have the old seals out of the bike and they dont even look that bad( the engine was fully rebuild by previous owner)


He did put in Boysen reeds and put on a Pro curcuit 304 silencer


could these few upgrades need me to increase my pilot jet?


the surging isnt bad the bike performs perfect, its just anoyying when costing down a hill, listening to the engine go ,voom,voom,voom or when i stop and idle. i just want it to be smooth xD ( only surges when its warmed up)

 

[t_bare]

Try higher octane gas. My 300exc did the same thing until I started mixing gas 1gal race gas to 4 gal premium pump 40:1 to oil

Good Luck
t_bare

 

[csdwarf]

Kind of forgot about this post, but the problem was the bike was lean.

I had just gotten the bike and it ran so great I didnt touch it, then started looking into this problem,

Pulled the carb to clean it, pilot jet was clogged, cleaned it out.

problem solved, then I had to put my needle back down because it was running rich from when I changed it testing!

Thanks guys for all the help, problem solved.

Btw, bike ran great all last summer, now its getting to the end of this year, getting it ready again!

what compression supposed to be on this bike? mine is like 230 or something really high.

at what point should these get a new piston rings ect.

 

[dirt bike dave]

Compression always measures high on the KTM 250. That's part of why they run so good.

The forged pistons tend to last a long time. Good thing, because they are expensive.

As for rings, if in doubt, might as well put some fresh ones in and inpsect the piston. If the piston shows signs of heavy wear, repalce it, too, but I probably would not order one until you are sure you need one.

After you get the fresh rings in, you can get a nice base line compression check number, and you can re ring again after it starts to drop.