78 cylinder vs 74

[Carl Hill]

Anyone ever put a 78 cylinder on a 74 250? The 78 model I used to ride was the best running air cooled KTM I ever rode.

[454MRW]

The transfer ports on 78 to early 1980 are more squared off and are overall a larger area so they do not match up exactly. I have a 77 bottom end that has had the transfer port area enlarged to match 78-E80. They can be matched relatively easily, but obviously require complete engine disassembly to ensure that no filings get into the bottom end. I am looking for an early 1980 cylinder to use on this modified 77 bottom end, because the early 1980s has a third boost port. I am not sure it was used before that, as all other 250's that I have seen only have two boost ports above the intake.
I know generally speaking the 78 and later bikes had a smoother more broader powerband than the earlier 73-77. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1978-1979 MX-6 175 & 250 KTM's
1976-78 125-400 RM's & 79 PE250 Suzuki & 2012 DR650
2007 CR125R Honda
1977 MC250 Maico