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I just learned the dirty secret about 1995 EXC 300 and 250 engines- This is the only model year that KTM made flat topped pistons. Consequently there are none to be found. What I have heard but don't know for sure- is that if I can find the domed 1994 cylinder heads for both the 250 and 300 motors, I can buy 1994 pistons and they will work in these 1995 motors. If anyone can tell me if this is possible, I'd be forever grateful!!

Thanks,
Maicoman
 

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Welcome to the forum...

I just learned the dirty secret about 1995 EXC 300 and 250 engines- This is the only model year that KTM made flat topped pistons. Consequently there are none to be found. What I have heard but don't know for sure- is that if I can find the domed 1994 cylinder heads for both the 250 and 300 motors, I can buy 1994 pistons and they will work in these 1995 motors. If anyone can tell me if this is possible, I'd be forever grateful!!

Thanks,
Maicoman

Well I would like to be able to help you on this one but it is beyond my limited knowledge.
Perhaps our resident experts, augdog, DW, axzon or cors might have some valuable insight pertaining to this issue of yours.
They seem to always have the answers, especially to these tough questions.
Post some pics of your '95 if you feel so inclined, we would enjoy seeing them.


Rangerman:ricky:
 

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Discussion Starter · #3 ·
Rangerman,

Thanks for shaking the bushes for some answers to my piston dilemma! Figured this would be the place to find a solution. At the moment both my 250 and 300 EXCs are basket cases, so all I could offer in the way of pics would be boxes of bones! This is my first jump into the KTM world. I'm an old guy racing Vintage 70's Maicos, but sick of getting my *** pounded by 6" of rear travel, and after I made the mistake of riding one of my buddy's newer KTMs, I was hooked on the possibilities of owning a plush ride! Once I figure out how to post pictures on this forum, I'll get some out there.

Thanks again,
Maicoman
 

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Did someone say Maicos???

Rangerman,

Thanks for shaking the bushes for some answers to my piston dilemma! Figured this would be the place to find a solution. At the moment both my 250 and 300 EXCs are basket cases, so all I could offer in the way of pics would be boxes of bones! This is my first jump into the KTM world. I'm an old guy racing Vintage 70's Maicos, but sick of getting my *** pounded by 6" of rear travel, and after I made the mistake of riding one of my buddy's newer KTMs, I was hooked on the possibilities of owning a plush ride! Once I figure out how to post pictures on this forum, I'll get some out there.

Thanks again,
Maicoman
I do believe that you and augiedoggie have more than just KTM's in common then.
Seems to me he has mentioned his persuasion toward the Mighty Maicos...490's to be exact...
Maybe he will chime in here in the near future to enlighten us some more about your original question and his affinity towards Maicos.


Rangerman:roost:
 

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Is no answer a good answer

Couldn’t help myself once I heard there were maico’s around. I remember the sound of those old dinosaurs as if it were 40 years ago:|
They were the top of the top and the cats pajamas back in the day. Amateurs rode jap bikes the experts rode maico’s. Damn things were expensive but worth it. You could wear out 2 Honda’s trying to keep pace with a maico on the track. Until the poor bastard needed parts. Grow a friggin beard down to your balls waiting for parts. Racers used to trade em for jap bikes while awaiting repair parts. No good answer on your vintage KATO piston problem. Dicks Racing may be helpful here. Those guys know their stuff. Maybe fix you up with some ideas or old parts. Be sure to post up pictures of your before and after project. Good luck
 

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i know by the time you messed about with old tech , guys like milltech would cobble a kit and from then on its easy rebuild, im assuming its a project worth keeping though.

https://www.millennium-tech.net/ktm_bbk.php
even if you cant find a kit they do take orders.milltech was a member here a while ago so give thenm a big ktm forums shout out.
 

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I just learned the dirty secret about 1995 EXC 300 and 250 engines- This is the only model year that KTM made flat topped pistons. Consequently there are none to be found. What I have heard but don't know for sure- is that if I can find the domed 1994 cylinder heads for both the 250 and 300 motors, I can buy 1994 pistons and they will work in these 1995 motors. If anyone can tell me if this is possible, I'd be forever grateful!!

Thanks,
Maicoman
Short answer is yes, absolutely. Get a head from a 93 or94 and you can use the dome top pistons from 93-94
 

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I just learned the dirty secret about 1995 EXC 300 and 250 engines- This is the only model year that KTM made flat topped pistons. Consequently there are none to be found. What I have heard but don't know for sure- is that if I can find the domed 1994 cylinder heads for both the 250 and 300 motors, I can buy 1994 pistons and they will work in these 1995 motors. If anyone can tell me if this is possible, I'd be forever grateful!!

Thanks,
Maicoman
Welcome to the forum.

We started riding KTM 2 strokes 12 years ago {mini's) and are now riding 150sx in MX2 racing. I can not remember any of our bikes having domed pistons. I think the same applies to 250 and 300 bikes.

As the later model pistons would be a fraction different in size and perhaps even have a different diameter pin, this would not be a direct fit for your bike. But coming from a background where fitting stuff that was not meant for where I fit it, and make it work, it would be interesting to know if todays KTM pistons can be made to fit by making some changes (re-bore, lower/raise cylinder, or similar). What are the the measurements of your old pistons?
 

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This might be good news, I have a 2000 KTM 250 EXC and it is a flat top. The 2008 I have apart is a dome top. I recently realized the difference and was intrigued about the performance differences. I run the Vertex 22650B kit. I have a brand new one here waiting for install so I can take some measurements for you with the micrometer and we can compare. Just show your measurements and I will measure the same spots.
Box reads:

KTM EXC 250cc, 00-05
STD Bore - Replica
D. 66.35 - Size B
Ring - 53010006640
Pin - 715372
Clips - 72074
 

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I just learned the dirty secret about 1995 EXC 300 and 250 engines- This is the only model year that KTM made flat topped pistons. Consequently there are none to be found. What I have heard but don't know for sure- is that if I can find the domed 1994 cylinder heads for both the 250 and 300 motors, I can buy 1994 pistons and they will work in these 1995 motors. If anyone can tell me if this is possible, I'd be forever grateful!!

Thanks,
Maicoman
I bought a 1995 Ktm 300exc and ran into the same problem a while back. What I ended up doing was buying a 1996 head and piston which both worked perfect. Surprisingly the 1996 piston is also flat so I’m not sure if a new head is even needed but my head needed replacement anyways. Ran perfect for a while but eventually seized because I had used the circlips from the old piston which were slightly to big for the new 1996 one I had bought. The old ones were just easier to install and remove then the ones that came with the new piston. Circlip ended up melted to the side of the Cylinder. Anyways I let it sit for a while and ended up buying a used 1996 cylinder thinking it would fit because the piston and head were from 96. Didn’t end up fitting so now my old cylinder is being repaired and replated and hopefully it will be back and running in the next month. Long story short, a 1996 piston and head work on a 95 cylinder; However don’t make the same mistake I made using wrong size circlips and also don’t try to get a 96 cylinder as it doesn’t fit to the bottom end of the engine. Hope that helps.
 
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