KTM "blunt" transfer ports?

[Big Mac]

Saw a post by Penton Larry awhile back about the KTM 400 cylinders going to a blunt transfer port in '76-'77, as the preferred setup.

No idea what a blunt vs. non-blunt transfer port is or looks like, but guess it mellowed out power delivery?? From the recent know-your-cylinders piece in SKT, looked like the 400 cylinder only came in the 81-1R and 82-2R codes for pre-78 and post-78 revisions or configurations on 81mm and 82mm stnd bores.

Any education on what blunt transfer ports are, what benefit they provided and how to spot them vs. earlier version?


Jon McLean
Lake Grove, OR

[Merlin]

............the port dividers,"blunt" vs "knifed"...............

[454MRW]

It looks like these differences are similar to the transfer port changes made to the 250 engines around 1978. The earlier transfer ports that I have seen on the 250 engines have more rounded, slightly smaller transfers with knife edged dividers until the 1978-early 1980 versions that have slightly larger squared off transfer ports similar to the 400 pictured. That combined with the torque style exhaust that came into use also around 1978 supposedly smoothed out the power band and made the bikes a lot more tractable. I have yet to tear into any of my 77-79 400 engines to compare the differences. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 250'S

[rob w]

Mike, The picture above is a 250 cylinder. Bob

[Big Mac]

Aha...so the blunt or squared off port dividers made the power delivery smoother with less hit?

Thanks, all you smart guys.

Jon McLean
Lake Grove, OR