350cc Trivia question

[marsattacks]

Mr. Jack Penton earned a gold in the 350cc class in the '73 ISDT riding a Penton. Was this a bored 250cc Hare Scrambler w/ a KTM engine or some other setup? Did the bike have model name? A precursor to the Mint?  Bultaco engines are essentially interchangeable at the top end so a 350 jug can be put on a 250 bottom end but not sure if any bigger bore KTMs were avail back in the day. Just curious. I don't know the answer. Thanks and regards.

[brian kirby]

The Penton 400 is really a 352cc engine so I suspect that is what he rode.

Brian

[marsattacks]

Seems reasonable. The "production guide" lists 400cc KTM engines for '74 but lists the Mint 400 w/ the 400cc as brand new in '74 1/2. Looks like the bike that was ridden in the ISDT was a gold tank.

Incidentally almost all the Pentons in that year's ISDT seemed (from pictures) to have large oval "Penton" decals on the tank. Some had small oval "KTM" decals too. I'd love to find a large oval Penton decal (or get a repro) since my December '73 Hare Scrambler had one (owner-applied I am guessing) that is now gone.

[brian kirby]

They may have been pre-production bikes? I really dont know anything about the time line of the bikes other than whats on the "production guide" page. Someone that was on the Penton team back then would surely remember.

Brian

[OUCWBOY]

We can guess at this all day, but if I were a betting man, I would go with what Rob says. However, you never know what tricks JP and KTM had up their sleeves at that time. Seems that the 250 prototype was around in 1971?? Could have been a trial of someting!?!?!

Donny Smith
Paragould, AR

[tomale]

My memory would never win any awards but it seems to me that the orginal engine design was built for a much larger engine displacement and they simply down sized to fit what ever size bike they wanted. thus a (400) was a step down, and to build a  350cc motor would not be that hard...the cool thing about that is that there would be no worry if the engine would handle the power...which in my mind meets JP's core values, "you can't finish first if you dont first finish" not sure who actually coined that....
Given the fact that the (400) is really a 352, what would it take to down size it just a few cc's... what about adding another base gasket... would that be enough?

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)
72'sixday (project bike)

[tmc3c]

Brother Dane!! Do you care to set the record straight? I had a call that said it was a 250cc bored to a 270cc.



Thomas Carmichael


1970 125 Six Day
1976 250 Hare Scrambler

[brian kirby]

Along the same lines, we had a discussion on another site of the late 70s 350 class bikes that were all 255-270cc. Most were 255cc, just couple mm overbore 250, so they could qualify for the 350 class. The Can-Am 350 for example was really a 270, a 4mm overbore 250. It would not surprise me if the bikes in '73 had done the same thing and been in the 255-270cc range.

Brian

[tmc3c]

Thomas Carmichael


1970 125 Six Day
1976 250 Hare Scrambler

[marsattacks]

Yes seems right. I saw a post from Herr Clausen regarding a Hercules 350 that was in fact a 250 overbored to 255. As they say its not the arrow its the indian anyway.