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CR250R@WINTERS · Jan 9, 2007

Hey guys,
At home, I am in the middle of going thru my 2004 250EXC and am just looking for any advice on installing the 250 SX piston and head mods on it. This is the first KTM rebuild for me. I have done many jap bikes, but this is the first KTM. I already have it all apart and I guess for the most part it’s like any jap 2 stroke.

One question I have for those that have done this mod before is: Since the SX piston is a dome piston and the EXC was a flat top, do I need to get that special little tool to measure the piston to head clearance or if you have the tool, is there any way you could actually measure the distance for me and let me know what it is. I imagine it will be fine, but since it is winter and I have the time, why not check it. Another question: I have always replaced the wrist pin bearing when changing pistons, but when I got my kit, which I assumed had it in it, there was not a new bearing. How many of you change them out every time? If you can think of any other tips, please let me know.

From what I hear it will be like a total different bike when its all bike together with the E3 pipe to boot. Sorry for the rambling, just kind’ve board here watching it snow out my window. Looks like winter has returned to Northern Michigan.

Oh, one other question: After installing the SX piston and head and the E3 pipe have you had to do any jetting changes?? Thanks again.

Fred T · Jan 9, 2007

CR250R@WINTERS said:
Hey guys,
At home, I am in the middle of going thru my 2004 250EXC and am just looking for any advice on installing the 250 SX piston and head mods on it. This is the first KTM rebuild for me. I have done many jap bikes, but this is the first KTM. I already have it all apart and I guess for the most part it’s like any jap 2 stroke.

One question I have for those that have done this mod before is: Since the SX piston is a dome piston and the EXC was a flat top, do I need to get that special little tool to measure the piston to head clearance or if you have the tool, is there any way you could actually measure the distance for me and let me know what it is. I imagine it will be fine, but since it is winter and I have the time, why not check it. Another question: I have always replaced the wrist pin bearing when changing pistons, but when I got my kit, which I assumed had it in it, there was not a new bearing. How many of you change them out every time? If you can think of any other tips, please let me know.

From what I hear it will be like a total different bike when its all bike together with the E3 pipe to boot. Sorry for the rambling, just kind’ve board here watching it snow out my window. Looks like winter has returned to Northern Michigan.

Oh, one other question: After installing the SX piston and head and the E3 pipe have you had to do any jetting changes?? Thanks again.

CR
I would suggest you also replace that wrist pin bearing since you don't want to go back in there. The "X" dimention I guess is measured with a piece of thick lead solder through the spark plug hole, then it's a matter of what thickness base gasket to use. I don't know those specs though. You let the piston smash the solder and then measure the thickness.

Clean up the power valve and make sure the flapper isn't getting into the piston at all after cleaning it. It shouldn't.

Your bike will run really sweet with a 38 pilot, NOZH #2 and 162/165 main. (40:1) This combo will give you a nice fat powerful bottom end that moves through the power band smoothly with a bit of a mid hit and then revs way out. You will love this mod and there is no downside to it really unless you really have issues with power and throttle control.

Might wanna check the reeds in the reed valve too while you are at it since it is a 2004.

CR250R@WINTERS · Jan 9, 2007

Thanks Fred,

I was hoping you might chime in. I will hava to look into what the best way to check the "x" dimensoin is. I know they make a tool to check it after putting the cylinder on and before installing the head. Off the top of your head, do you remember your air-screw setting?

Wolverine423 · Jan 9, 2007

You will probably find that a .004 base gasket to work best.

Fred T · Jan 9, 2007

CR250R@WINTERS said:
Thanks Fred,

I was hoping you might chime in. I will hava to look into what the best way to check the "x" dimensoin is. I know they make a tool to check it after putting the cylinder on and before installing the head. Off the top of your head, do you remember your air-screw setting?

1 turn +/- 1/2 turn. Adjust it as temps change.

salgeek · Jan 9, 2007

I could have sworn I read on KTMtalk that if you change to the SX piston it is advisable to change to the SX dome/head [jug is the same]???

IMO - there is no need to replace the wrist pin bearing. Change it along with the wrist pin if the pin is groved due to ingestion of a foreign substance such as dirt or sand.

Scott

Fred T · Jan 9, 2007

salgeek said:
I could have sworn I read on KTMtalk that if you change to the SX piston it is advisable to change to the SX dome/head [jug is the same]???

IMO - there is no need to replace the wrist pin bearing. Change it along with the wrist pin if the pin is groved due to ingestion of a foreign substance such as dirt or sand.

Scott

His words are below so he is installing the SX head and domed piston.

installing the 250 SX piston and head mods on it.

salgeek · Jan 9, 2007

Thanks FredT... Should have read more carefully. :cool:

jackdrinker · Jan 10, 2007

salgeek said:
I could have sworn I read on KTMtalk that if you change to the SX piston it is advisable to change to the SX dome/head [jug is the same]???

IMO - there is no need to replace the wrist pin bearing. Change it along with the wrist pin if the pin is groved due to ingestion of a foreign substance such as dirt or sand.

Scott

It's like $10 and already out... No need to skimp now..
You could get some plasti-gage and I have used modeling clay in the past..

KTM Mike · Jan 10, 2007

Mike - I think I have some plasti gauge at home if you need some.

Yup..boring here to....

crazytrails · Jan 17, 2007

Sounds Like The Bike Is Going To Rip. Good To Hear You All Are Stayin Busy.
And Whats With This Watching The Snow Thing, Us Dirt Riders Down Here In Muskegon Stud The Good Old Bikes Up With Kold Kutters And Ride All Year Long. :nod:

Wolf Child · Jan 17, 2007

Fred T said:
CR
I would suggest you also replace that wrist pin bearing since you don't want to go back in there. The "X" dimention I guess is measured with a piece of thick lead solder through the spark plug hole, then it's a matter of what thickness base gasket to use. I don't know those specs though. You let the piston smash the solder and then measure the thickness.

Clean up the power valve and make sure the flapper isn't getting into the piston at all after cleaning it. It shouldn't.

Your bike will run really sweet with a 38 pilot, NOZH #2 and 162/165 main. (40:1) This combo will give you a nice fat powerful bottom end that moves through the power band smoothly with a bit of a mid hit and then revs way out. You will love this mod and there is no downside to it really unless you really have issues with power and throttle control.

Might wanna check the reeds in the reed valve too while you are at it since it is a 2004.

so this is what I'm in for? heh heh...sounds sweet. Be prepared to have your brain picked clean. :laugh:

TCTrailrider · Jan 17, 2007

Wolf Child said:
so this is what I'm in for? heh heh...sounds sweet. Be prepared to have your brain picked clean. :laugh:

Wolfy, read it again.

"You will love this mod and there is no downside to it really unless you really have issues with power and throttle control."

Sound like anbody you ride with? :laugh: Enjoy, your gonna like that bike.

Wolf Child · Jan 17, 2007

TCTrailrider said:
Wolfy, read it again.

"You will love this mod and there is no downside to it really unless you really have issues with power and throttle control."

Sound like anbody you ride with? :laugh: Enjoy, your gonna like that bike.

under powered and overweight bikes do not count in this equasion. :nener:

CR250R@WINTERS · Jan 19, 2007

Hey Crazytails,

I guess I am not as die-hard as you southern boys are about riding in the winter. Unless you are talking about a snowmobile. The bike gets a little R&R and a good rebuilb in the winter. Makes for some good quality time in the shop wrenching and having a few cold ones along the way.

And yeah, you probably won’t be able to keep up with that RM of yours after I am done with the rebuild. See you in the spring! KTM rules.... :nener:

slowone · Jan 19, 2007

I'm not trying to hijack this thread! Anybody have jetting info for a stock 2006 250xc-w. I'm in Michigan and curious what people are doing to the stock 250's for jetting.

Fred T · Jan 19, 2007

Nick
Try a NOZH #2, stock pilot and a 162. Options on this are 38 pilot and a 165 main. Any variation of these jets. I find the air screw once jetted properly will fine tune if for just about any day. Good luck. What is your stock needle? I'll compare to what came in my 2007. My stocker was pretty good and some guys just move it to #3 from #4. If mine is different from yours I'll let you try mine.

FT

D.LEATHERS · Jan 19, 2007

Nick,
I Can't Believe That B.v. Didn't Have Your Scoot All Dialed In, He Rode It All Season Long In 2006. He Is Very Particular About His Bikes, It's Hard To Believe He Would Have Not Fine Tuned The Jetting To Be Nice And Crisp.

Dave L.

crazytrails · Jan 22, 2007

Hey, Lets Not Dog The Suzuki Mr. Winters. :yell: I Have A General Location Where You Live. :laugh: Im actually doing some engine mods to the bike also. Hopefully it will be different bike when im done. :p

3KDXXR2 · Jan 22, 2007

Hey Aaron what mod are you doing? Putting the yz engine in it :)

woodsy · Jan 22, 2007

Curtis,
Not sure how much swappin in a YZ motor would do em anyway,, he still has a few things to learn on that RM before moving up to a REAL motor :laugh:
Hey,, wait a minute.. He did whip all of us at Chaos Harescramble 2 years ago on a YZ250,, then he moved to Suzuki last year and cleaned house again.. Maybe I oughta shut up eay :whoa:

CR250R@WINTERS · Jan 23, 2007

Hey Aaron what mod are you doing? Putting the yz engine in it

Now that is funny!! :laugh:

Woodsy, Woodsy, Woodsy...........it sounds to me you are trying to turn Chaos into a competition. Most everyone there (except Aaron) realizes it is all for fun. :nener: Maybe next year we will have to have a competitve class......

KTM Mike · Jan 23, 2007

For those mods to be IMPROVEMENTS that motor would of course need to have been made in Austria.... not yapland

As I recall the official results, it seems it was a green bike and an orange bike that took official top honors...not a yeller one. We could consider some changes in scoring I guess.... lets see...I got it. Base Scoring on a color coded system as follows First Place: Orange Second Place Orange Third: Orange All other colors follow in order of Green, Red, Blue, Yellow....I like that plan.

bbarel · Jan 23, 2007

What was the competition?
Who can eat the most hot dogs?

crazytrails · Jan 23, 2007

hey now, cant everybody just get along. ;) And by the way, camp chaos is a race. its a race against yourself, just like enduros. i just ride until im tired, as should everyone else. Now don't make me tell YOUNG TEDDERS to yell at ya alll. :yell:

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