KTM big bore kit.

[evo550]

Does anyone know if there is such thing as a big bore kit avaliable for Ktm 250 sx (current version).
I know that there is a 300 upgrade kit avaliable through KTM, but it's alot to pay for 50 extra cc's, I was hoping for something along the 350 to 400 kit.
I was wanting to do a service honda version to my KTM but I think a full 500 might be a bit too big for me........unless there is a De bore kit for a 500 I don't know about.

[evo550]

I will take the silence as a no 
OK try another approach, has anyone had any experience with the '02 (roughly) KTM 380 motor, and any chance they will fit the current 250sx chassis.
I expect at least 10 replies on this by this afternoon, so get busy people

[JohnN]

From the feedback from others, that 300cc kit is the cats meow! While it's only 50cc's more than the 250, it brings the horsepower and torque up to a more equal number as the 450F lawn mowers...

While remaining light, easy to handle and fast, nice combination.

Not very familiar with the KTM's and I've never even seen a 380.

[admiral]

I will take the silence as a no 
OK try another approach, has anyone had any experience with the '02 (roughly) KTM 380 motor, and any chance they will fit the current 250sx chassis.
I expect at least 10 replies on this by this afternoon, so get busy people

i have a '99 380SX that i bought brand new that i have been wanting to get the motor into a modern KTM chassis. really i'm waiting to buy the finished product because i'm too lazy to do it myself. i did all the measuring for the job back in '08 and started looking for a rolling chassis. the 'Y' section of the front down tube/engine cradle has to be modified. the engine mounts don't fit and the cases have to be bored for the larger swingarm pivot bolt. head stay is different. engine mounts are the easy part to overcome. the 380 motor (and all '98-'02 250's and 300's) have a resonance chamber on the front of the motor that will hit the frame at the 'Y' section. i have seen some people who have done the conversion just fab up a flat plate to replace the chamber with. doing it this way would save the most grief as you could weld up the motor mounts and  then bore the cases for the swing arm and hang the motor in. the pipe even fits in the existing mounts. i saw another conversion that cut the 'Y' section out and welded in a new one along with a new cradle and engine mounts to fit properly like Service Honda would do. i have seen a third one which was the craziest one of all. believe it or not the 380 crank fits in the new generation cases and the jug bolts on. this guy had slipped it together on one of those electric start 300 models. the primary gear on the 380 crank didn't work with the clutch basket gear though. he had to modify it somehow, i can't remember exactly. i think he had to modify the 300's gear to fit the 380's crank or he made a whole new one. i do remember that the cases finally cracked and broke at the kick starter shaft. there had been incidents of people breaking the original 380 cases in that area although my bike never had any problems. so i think that the 380 crank/new generation cases is not the way to go even though it was a neat idea. i wish i could just buy the rolling chassis set up ready to accept the engine out of my bike. no muss no fuss. and John, if you are ever in the midwest (MO/IL) and want to ride the 380SX feel free to get in touch with me. it is retired from MX and i only use it the few times a year i trail ride. it's the back up bike to my 250SX now.

[JohnN]

Admiral - thank you very kindly for the offer to ride the 380!! If I'm out that way, I'll be sure to let you know.

 

[offroader]

On the ktm talk site under the oldies section search for 08 super 380.The guy that did the 380 swap to 08 chassis name is Dave.He was selling a frame not that long ago  ready for the 380 engine.You can also find the 380 to new cases swap on there.Personally I would rather just swap the whole 380 engine to the lmc.

[maicoman009]

I would definetely go with KTM's 300cc big bore kit! I own a 2008 KTM 300xc & it seems to be the perfect bike for the mostly woods riding that I do! I've had the opprotunity to ride my buddys 08 KTM 250sx & those bikes RIP!!! I can only imagine what the 250sx would run like with the 300cc big bore kit.One of the few mods I've done to my 300xc is install an F-2 carb splitter & I was actually quite shocked when I noticed a pretty decent gain to the low end & even into the midrange! I know that KTM"s 300 big bore kit is a bit pricey however I do believe I would have to go with that instead of the older 380cc engine.Even with my 300xc after I installed the F2 along with the FMF FATTY pipe & Turbine Core silencer it definitely gained a good bit more HP as well as more torque! One thing I will say though is when I installed the F2 in the carb I had to use a very small amount of JB Weld to secure it in the carb.

[ktm111]

I put a 300cc top on a 06' 250sx way cool . If you a vet rider or run in a 450 class it's the way to go. Call munn racing (888)850-7473 they sell a 300sx kit and you get everything you need to convert over for around $700.00 otd. It sounds like alot but think about what your getting. head,cycl,piston,rings,p.v. parts,gaskets,and ign. box.     KTM111