MC5 TOP END

[Grunter215]

PULLED THE BARREL OFF MY 1976 KTM 250 MC5 TODAY...LOOK INSIDE...AND THE LINER IS CRACKED BETWEEN PORTS!! QUESTION IS ARE THE '76-'78 BARRELS THE SAME, IM THINKING THEY ARE BUT NOT 100% SURE.ARE THE HEADS ALL THE SAME? CHECKED AL BUEHNER KTM FOR LINER BUT SOLD OUT.CHEERS

[MauriceR]

There is  78 top end on ebay right now, he says it measures 71.17 so that should be standard bore
http://www.ebay.com/itm/1978-KTM-250-MC5-Top-End-Assembly-Ahrma-Vintage-MX-/390622665010?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item5af2ecd932

[Slakewell]

Yes the 78 top end is a direct bolt on with a little bit more power as there is a extra port.

[ozktm]

Guys, you need to look at the base of the barrels where the transfer joins the cases.
The early barrels are and eliptical shape.
The late barrels are square shaped. Need to confirm when this changed.

If you use either on the wrong style cases they wont match too well in this area.
Picture coming later to show you.

Just check this area before you purchase one, as some guys don't even get the year model of their bike correct when they part it out.

Cheers,
Adrian.

[Grunter215]

The markings on top of piston.....71 - 2 - ELKO - 1274a. Whats the 2 mean??

[ozktm]

Basically there were two types of pistons.
Single ring and twin ring with the top ring being a dykes 'L' ring.

Depending on what size you need, Al B could have new modern wiseco pistons that are twin thin rings.

But the Mahle piston you have is getting harder to find in oversizes.

[Grunter215]

Thanks Adrian. Looked at another barrel but that was square transfer so anybody got a good usable oval transfer barrel to sell Or a bore sleeve to suit ??

[ozktm]

http://www.ebay.com/itm/1974-KTM-Penton-250-Hare-Scrambler-Cylinder-Barrel-/190422484373?pt=Motorcycles_Parts_Accessories&hash=item2c56108595&vxp=mtr

[ozktm]

http://www.ebay.com/itm/1975-KTM-Penton-250-Hare-Scrambler-Cylinder-Barrel-/350311071844?pt=Motorcycles_Parts_Accessories&hash=item51902ac064&vxp=mtr

[Grunter215]

Thanks Adrian. Question KTM boys...My 1976 250 MC5 motor and a 1978 250 GS motor, whats the same/different??Are MC/GS 250 54 cases the same. Will internals swap over? Rather than chase a barrel ,the whole motor option might be better. I contacted the above ebay items,asked about condition of bore etc, contact stopped,no replies. Also looked into getting bore liner made...thats a possible option. So now a GS motor come up,so hence the question...are they the same?

[Slakewell]

Someone on here the other day was selling a 78 motor. Yes you can just keep the bottom cases and swap them over. There is no real power advantage.